PR-483
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HORTICULTURAL CROPS—BLACKBERRIES
John Strang, April Satanek, John Snyder, Chris Smigell, Doug Archbold, Phillip Bush, Dave Lowry, and Darrell Slone, Department of Horticulture
Blackberries continue to be a popular market item for Kentucky consumers, and most growers find that high-quality blackberries are readily marketable. This study is being conducted as part of the New Crop Opportunities Fruit Project at the Horticulture Research Farm in Lexington, Kentucky. The first part of the study has been designed to evaluate two training systems for three thornless, semi-erect blackberry varieties using a double-T four-wire trellis. The second part is to evaluate the use of a plastic bailing-twine trellis for cane stabilization versus no trellis for two thornless, erect blackberry varieties.
Semi-erect thornless blackberry plants were set the spring of 2000 into black plastic-mulched beds. Each plot consisted of three plants of either Hull Thornless, Triple Crown, or Chester spaced 8 feet apart in the row with 12 feet between rows. Each plot was replicated three times in a randomized block design. All plants were trained on a double-T four-wire trellis with the lower two wires 2 feet apart and the top two wires 4 feet apart. Two training systems were useda conventional system and the Oregon system.
In the conventional system, primocanes were topped when they had extended 1 foot above the top of the trellis. Dead fruiting canes that had cropped were removed in the fall. During early spring dormant pruning, spindly canes and/or those that had red-necked cane borer swellings were removed. Lateral branches were pruned back to 18 inches in length, and those that were within 18 inches of the ground were removed completely.
Primocanes were not summer tipped for the Oregon system. In the spring, canes were not thinned, although those with red- necked cane borer swellings were removed. Low laterals, within 18 inches of the ground, were removed. Laterals above this were not cut back and were wound around, and sometimes loosely tied, to the closest trellis wire extending away from the plant.
Arapaho and Apache erect blackberry plants were set 3 feet apart in the guard rows on the north and south sides of the semi-erect blackberry plot. Trellising treatments (supported and unsupported) and varieties were each replicated three times in a completely randomized design. Plots consisted of three plants of the same blackberry variety. Metal fence posts were set at intervals of 9 feet and plastic bailer twine was run on both sides of the supported treatment at a height of 3.5 feet.
During the first (2000) growing season, canes were allowed to trail and grow as much as possible. In the spring of 2001, the erect blackberry canes were pruned severely to encourage the development of more vigorous shoots for the following season. During the summer of 2001 and 2002, primocanes were tipped at a height of about 3 feet. Spindly canes and those with red-necked cane borer swellings were removed in the spring of 2002. Laterals were cut back to a length of 16 to 18 inches.
The black plastic mulch was removed during the spring of 2001, and plants were watered by hand as needed. The summer of 2002 was dry, and a trickle irrigation system was installed. Plants were fertilized in February with calcium nitrate at the rate of 8 lb/100-foot row (43.5 lb N/A). Weeds were controlled by hand weeding, spot treatment with Roundup® and in 2002 with Princep 4L. A conventional fungicide spray program using Kocide, Captan, Nova, and Benlate was maintained. Japanese beetles and green June beetle pressure was severe in 2002, and both Sevin and malathion were used for control. Bird pressure was also severe early in 2002, and an avian alarm was set up. The plants were harvested in 2001 and 2002. Data were collected for yield, fruit size, and fruit soluble solids.
Analysis of the 2002 data suggested that there was a mix-up in labeling of the Arapaho and Apache plants at planting. A visual inspection of the plants during the dormant season indicated that this was so. Arapaho canes remain green during the winter, while Apache canes turn red. Plants and plots were subsequently relabeled, and the data analysis was corrected. This resulted in the loss of precision in the 2002 data.
Statistical analysis was not conducted on the 2001 yield data (Table 1), but trends for berry weight and soluble solids (% sugar) content were similar to those obtained in 2002. Triple Crown tended to be the highest yielding and Hull Thornless the lowest yielding in 2001, while this was reversed in 2002, although there was no significant difference in yield. The fruit load in 2001 could have been responsible for the reversal in 2002. Arapaho and Apache had very low yields in 2001 due to severe spring pruning.
Results for the semi-erect blackberries for 2002 are presented in Tables 2, 3, and 6. There were no significant differences in yield between the three semi-erect blackberry varieties or between training systems. Triple Crown had a larger berry size than the other two varieties. Triple Crown berries also had 1.3% higher soluble solids (sugar) content than Chester, which in turn had 2% higher soluble solids content than Hull Thornless. The Triple Crown fruit were noticeably sweeter than the other berries. They also had a higher pH (Table 6) than Chester and Hull Thornless. Pickers felt that Triple Crown had the most attractive looking fruit. Average berry size was slightly larger for the conventional training system in contrast with the Oregon training system. There was no difference in berry pH between the conventional and Oregon training systems (data not shown).
Results for the erect blackberries are indicated in Tables 4 and 5. There was no difference in yield, average berry weight, or soluble solids content between the Apache and Arapaho plants. Nor was there a difference in yield or berry weight between the no-trellis and string-trellis treatments. However, there was a trend for Apache to yield more than Arapaho and for the string-trellis plants to yield more than the no-trellis plants. These trends may become more apparent in future harvests as a mix-up in the Arapaho and Apache plants at planting, which resulted in a loss of two degrees of freedom in the 2002 analysis, is rectified. The string-trellised plants did have slightly lower soluble solids content. Berry pH did not differ between the Arapaho or Apache varieties, and this was not affected by trellising (data not shown). Bird losses were more severe on the erect blackberries because these were the first to ripen. Pickers indicated that of the two thornless erect blackberries, Apache had the more attractive fruit.
| Table 1. Thornless blackberry yield, berry weight, and soluble solids, 2001 harvest. | ||||
| Variety | Average Yield (lb/A) | Average Berry Wt. (g) | Soluble Solids (%) | |
| Triple Crown | 6,471 | 7.6 | 10.0 | |
| Chester | 5,908 | 5.2 | 7.6 | |
| Hull Thornless | 1,897 | 5.5 | 6.5 | |
| Apache1 | 2,517 | 8.0 | 11.4 | |
| Arapaho1 | 353 | 4.3 | 11.7 | |
| 1 | The erect thornless blackberries were pruned severely the spring of 2001. | |||
| Table 2. Thornless semi-erect blackberry variety yield, average berry weight, and soluble solids, 2002 harvest. | ||||
| Variety | Yield1 (lb/A) | Average Berry Wt.1 (g) | Soluble Solids1 (%) | |
| Hull Thornless | 13,459 a | 5.4 b | 8.6 c | |
| Chester | 10,865 a | 5.2 b | 10.6 b | |
| Triple Crown | 9,815 a | 6.9 a | 11.9 a | |
| 1 | Numbers followed by the same letter are not significantly different (Duncan Waller LSD P = 0.05). | |||
| Table 3. Thornless semi-erect blackberry yield, average berry weight, and soluble solids based on training system, 2002 harvest. | ||||
| Training System | Yield1 (lb/A) | Average Berry Wt.1 (g) | Soluble Solids1 (%) | |
| Conventional | 10,722 a | 6.0 a | 10.3 a | |
| Oregon System | 12,037 a | 5.7 b | 10.4 a | |
| 1 | Numbers followed by the same letter are not significantly different (Duncan Waller LSD P = 0.05). | |||
| Table 4. Thornless erect blackberry variety yield, average berry weight, and soluble solids, 2002 harvest. | ||||
| Variety | Yield1 (lb/A) | Average Berry Wt.1 (g) | Soluble Solids1 (%) | |
| Apache | 6,131 a | 6.6 a | 10.6 a | |
| Arapaho | 2,947 a | 7.0 a | 10.9 a | |
| 1 | Numbers followed by the same letter are not significantly different (Duncan Waller LSD P = 0.05). | |||
| Table 5. Thornless erect blackberry yield, average berry weight, and soluble solids based on training system, 2002 harvest. | ||||
| Training System | Yield1 (lb/A) | Average Berry Wt.1 (g) | Soluble Solids1 (%) | |
| No trellis | 3,786 a | 6.0 a | 11.0 a | |
| String trellis | 5,291 a | 7.6 a | 10.4 b | |
| 1 | Numbers followed by the same letter are not significantly different (Duncan Waller LSD P = 0.05). | |||
| Table 6. Thornless semi-erect blackberry pH, July 9, 2002, harvest. | ||
| Variety | Berry pH1 | |
| Triple Crown | 3.2 a | |
| Chester | 2.9 b | |
| Hull Thornless | 2.9 b | |
| 1 | Numbers followed by the same letter are not significantly different (Duncan Waller LSD P = 0.05). | |
Joe Masabni and Dwight Wolfe, Department of Horticulture
In the spring of 2000, a blackberry cultivar trial was established at the University of Kentucky Research and Education Center, Princeton, Kentucky.
The trial consisted of five cultivars, Navaho, Arapaho, Apache, Kiowa, and Chickasaw, allocated to five replications or blocks in a randomized complete block design. Each cultivar-replication combination consisted of a 10-foot-long plot followed by a 5-foot-long grass area to serve as a buffer. Plots consisted of six plants spaced 2 feet apart within each plot and 14 feet between rows. Plants grew well and looked healthy throughout the season of 2000. However, in 2001, all Navaho plants developed symptoms of Tobacco Ring Spot Virus. Navaho plants were removed during the fall of 2001 after laboratory confirmation of virus infection. In 2002, plots were harvested between June 18 and Aug. 1, on a two- to six-day schedule as dictated by the ripening process. Yield and berry size (weight of 50 berries per plot) data were recorded at each harvest, and total yield and average berry size calculated.
Results are shown in Table 1. Arapaho ripened the earliest but also had the lowest yield. Conversely, Apache yielded the most fruit but was also the last to ripen. Kiowa and Chickasaw were intermediate between Apache and Arapaho in both yield and ripening date. Arapaho had the shortest harvest period of 25 days, followed closely by Chickasaw with 39 days. Kiowa had the longest harvest period of 44 days.
In 2002, Chickasaw plants showed symptoms of Impatiens Necrotic Spot Virus and were subsequently removed.
| Table 1. 2002 blackberry yield and fruit size of the 2000 blackberry cultivar trial at the UK Research and Education Center, Princeton, Kentucky. | ||||||
| Cultivar | Yield (lb/A) | Berry Size (g/berry) | Percent Fruit Ripened By | Harvest Period | ||
| June 30 | July 15 | |||||
| Apache | 9,801 | 7.6 | 3 | 64 | 6/27-8/1 | |
| Kiowa | 7,499 | 8.7 | 19 | 71 | 6/18-8/1 | |
| Chickasaw | 6,192 | 7.0 | 17 | 85 | 6/18-7/26 | |
| Arapaho | 3,454 | 3.5 | 76 | 100 | 6/18-7/12 | |
| * LSD (5%) | 2,987 | 0.9 | NA | NA | NA | |
| * | LSD = Least significant difference at the 5% level. | |||||
Charles T. Back and R. Terry Jones, Department of Horticulture
Blackberry (Rubus), a native plant, grows well in Kentucky, and new improved blackberry cultivars offer a chance for crop diversification and a high income per acre crop for Kentucky agricultural producers. Blackberries have multiple uses, including fresh or processed consumption, wine production, and medicinal purposes. Rubus has lower establishment and labor costs than many horticultural enterprises. It is also important to note that blackberries have the potential to be grown on hilly land and strip mine sites and have a low erosion potential in conjunction with sod strips. With available mechanization, blackberries can be grown on a large scale and mechanically harvested, or they may be grown on small scale and hand-harvested for local fresh markets.
A thorny and thornless blackberry cultivar and advanced breeding selection trial was planted as a randomized complete block in May 2000 on raised beds. For the thorny cultivars, six plants/replication were planted 2 feet apart in the row. The thornless erect cultivars were planted with four plants/replication at a spacing of 3 feet in the row. Plants of a thornless semi-erect cultivar (Triple Crown) were planted 4 feet apart in the row with three plants per replication. All rows were spaced 8 feet apart. There were a total of five replications for all the cultivars and selections with a 3-foot space between replications. The blackberries received a single application of 50 lb actual N/A from ammonium nitrate in March of 2001, 2002, and 2003. The blackberries were observed for vigor, winter/spring hardiness, disease problems, as well as fruit yield, berry size, appearance, and firmness.
Many thorny and thornless blackberry cultivars have a tendency to de-harden and break dormancy early in Quicksand where 60° to 70°F temperatures in January and February may be followed by 10° to 20°F temperatures in March and April. This weather pattern occurs at least once every four or five years and did so in 2002 and 2003. Thornless cultivars such as Hull and Triple Crown, while considered less hardy than thorny blackberries, do very well here under our growing conditions because they are slow to break bud and remain dormant later into the spring. Table 1 shows the bloom development and the presence of floricane injury for both years. Canes showing injury at that time tend to die during warm weather prior to harvest, reducing yield and berry quality. Entries or selections preceded by an "A" and followed by a number are unreleased breeding selections, are not for sale, and are not available commercially at the time of this testing and reporting.
The 12 cultivars being tested at Quicksand were evaluated three years after planting for survival (Table 3). A grower who invests $2,700 to $3,300 in order to establish an acre of blackberries needs at least two good fruiting years to break even and begin making a profit. Among the 12 cultivars being tested, eight still had plant stands of 80% or better, whereas four of the cultivars had stands of 60% or less. An unidentified Phytophthora species was isolated from the decaying roots of many of the blackberry cultivars with poor stands.
Yield and berry size of the three thorny blackberry cultivars tested are shown in Tables 4 and 6. Kiowa produced the highest average yield (5,675 lb/A) and had the least amount of visible cane injury. Unfortunately, Kiowa is very susceptible to a fungal disease called double blossom. In a warm, humid climate, it would be hard to raise Kiowa without having a good fungicide spray program. Kiowa canes also have a tendency to lie down, thus making picking and mowing difficult. The selection A1854 had a tremendous fruit set in 2002, but the injured floricanes in all five reps slowly went down hill, resulting in a smaller berry size. The plants did not recover and have died out (Table 2). Shawnee had an average yield of 5,566.5 lb/A and has an attractive berry but is also subject to cold temperature floricane injury. In past trials at Quicksand, Shawnee has had problems with hardiness and double blossom and was included in this trial as a check for those problems.
The highest yielding thornless blackberry (Tables 5 and 6) was Triple Crown (8,102 lb/A) followed by A1689 with a two-year average of 5,173 lb/A and Ouachita (A1905) with 4,919 lb/A average. The three cultivars A1857, Navaho, and A2049 all suffered severe floricane injury and plant death. In 2003, the fruit from Navaho were so small and dried they were not marketable. The plants died out in 2003. The numbered cultivars A1689 and Ouachita (A1905) appeared to suffer less cane injury and produced attractive fruit. The fruit quality of these two selections made them the "pickers' choice" among all the blackberries harvested the past two years. Additional tests are needed to determine the long-term suitability of any blackberry cultivar to our climatic conditions, and further tests are planned for 2004 on these and additional blackberry cultivars and selections planted in 2002.
| Table 1. Blackberry cultivar/selection bloom and floricane evaluation. | |||||||||
| Cultivar/Selection* | Percent Full Bloom | Floricane Injury | Comments | ||||||
| 5/04/02 | 4/25/03 | 5/04/02 | 4/25/03 | 5/04/02 | 4/25/03 | ||||
| A1963 | 0 | 0 | injury | 8% | 3/5 reps visible injury | 4/5 reps visible injury | |||
| A1539 | 80 | 30 | none | 10% | - | 4/5 reps visible injury | |||
| A2049 | 48 | 50 | injury | - | 3/5 reps visible injury | plants died out | |||
| A1857 | 37 | 0 | injury | 40% | 2/5 reps visible injury | 4/5 reps injury | |||
| A1854 | 98 | 45 | injury | 10% | 1/5 reps visible injury | plants dead 3/5 reps | |||
| A1960 | 15 | 0 | injury | 76% | 4/5 reps visible injury | 5/5 reps injury | |||
| A1689 | 1 | 0 | slight injury | 0 | 1/5 reps visible injury | 0/5 reps injury | |||
| Ouachita (A1905) | 6 | 0 | none | 5% | 1/5 reps injury | ||||
| Navaho | 1 | 0 | severe injury | 65% | 4/5 reps severe injury | 5/5 reps injury plants dying | |||
| Kiowa | 5 | 0 | none | 17% | - | 5/5 reps injury | |||
| Shawnee | 61 | 11 | none | 7% | - | 5/5 reps injury | |||
| Triple Crown | 0 | 0 | none | 0 | - | 0/5 reps injury healthy plants | |||
| * | Entries or selections preceded by an “A” and followed by a number are unreleased breeding selections and are not available commercially at the time of this testing and reporting. | ||||||||
| Table 2. 2003 blackberry cultivar survival evaluation. | ||||||||||
| Cultivar* | Date | Plant1 No./Year | Avg. No. Floricanes2 | Avg. % Floricane Injury3 | Avg. No. Primocanes4 | Disease Rating5 | Comments | |||
| 2000 | 2001 | 2003 | ||||||||
| A1963 T6 | 7/28 | 6 | 5.8 | 5.6 | 18 | 78 | 16.8 | 0 | good regrowth | |
| A1539 T | 7/28 | 6 | 5.2 | 5.2 | 9.8 | 74 | 15.8 | 0 | good regrowth | |
| A2049 T | 7/28 | 6 | 5.8 | 1.6 | 0.4 | - | 0.4 | - | dead/dying plants | |
| A1857 T | 7/28 | 6 | 6 | 5.0 | 10.6 | 90 | 8.8 | - | 3/5 reps dying | |
| A1854 | 7/28 | 6 | 5 | 3.2 | - | - | - | - | 5/5 reps dying | |
| A1960 T | 7/28 | 6 | 6 | 3.6 | 6.4 | 92 | 5.8 | - | 5/5 reps dying | |
| A1689 T | 7/28 | 4 | 2.4 | 4 | 5.2 | 74 | 12 | - | 2/5 reps dying plants | |
| Ouachita (A1905 T) | 7/28 | 6 | 5.2 | 4.8 | 14.2 | 88 | 11.6 | - | 4/5 reps good regrowth | |
| Navaho | 7/28 | 4 | 4 | 2.4 | 5.2 | 57 | 4.6 | - | 5/5 reps dying out | |
| Kiowa | 7/28 | 6 | 4.6 | 5 | 10 | 90 | 7.6 | DB | 3/5 reps dying out | |
| Shawnee | 7/28 | 6 | 5.6 | 5.8 | 11.4 | 92 | 13 | DB | good regrowth | |
| Triple Crown | 7/28 | 3 | 3 | 3.6 | 7.2 | 1 | 9.4 | 0 | 5/5 reps healthy | |
| * | Entries or selections preceded by an “A” and followed by a number are unreleased breeding selections and are not available commercially at the time of this testing and reporting. | |||||||||
| 1 | Number of live plants/rep. | |||||||||
| 2 | Number of floricanes present. | |||||||||
| 3 | Percentage of injury or death to the floricanes: 0 = no injury,1 = 10-20% death while 5 = 80-100% death. | |||||||||
| 4 | New primocane present actual count/rep. | |||||||||
| 5 | Presence of disease: DB = Double Blossom, OR = Orange Rust, PH = Phytophthora Root Rot; 0 = no disease, 5 = 100% diseased. | |||||||||
| 6 | “T” means the cultivar is thornless. | |||||||||
| Table 3. Survival of blackberry cultivars after two years. | ||
| Cultivar* | Percent Plant Survival1 | |
| A1963 T | 93 | |
| A1539 T | 87 | |
| A2049 T | 27 | |
| A1857 T | 84 | |
| A1854 | 53 | |
| A1960 T | 60 | |
| A1689 T | 100 | |
| Ouachita (A1905 T) | 80 | |
| Navaho | 60 | |
| Kiowa | 83 | |
| Shawnee | 97 | |
| Triple Crown | 100 | |
| * | Entries or selections preceded by an “A” and followed by a number are unreleased breeding selections and are not available commercially at the time of this testing and reporting. | |
| 1 | Blackberry survival after two full years. Plant survival is based on live plants in five replications. | |
| Table 4. 2002 thorny blackberry cultivar/selection evaluation, Quicksand. | ||||||||||
| Cultivar/Selection* | Harvest Start1 | Harvest Days2 | Pounds Fruit/A | Fruit Size (oz) | Taste3 | Appearance4 | % SS5 | Disease Rating6 | Remarks | |
| Kiowa | 6/27 | 40 | 7185 A | 0.322 | T | A+ | 8.0 | 2.4 | Double Blossom | |
| A1854 | 6/18 | 35 | 4052 A | 0.123 | S,T | A | 9.0 | 0.6 | ||
| Shawnee | 6/20 | 36 | 4010 A | 0.382 | S | A | 8.4 | 2.5 | Double Blossom | |
| LSD | 3805 | 0.478 | ||||||||
| * | Entries or selections preceded by an “A” and followed by a number are unreleased breeding selections and are not available commercially at the time of this testing and reporting. LSD 5% Least significant difference at the 5% level. | |||||||||
| 1 | The first day of harvest for that cultivar. | |||||||||
| 2 | The number of days between first and last harvest for each cultivar. | |||||||||
| 3 | Taste of fresh fruit: T = tart, S = sweet, B = bland. | |||||||||
| 4 | Appearance: A- = below average, A = average, A+ = above average. | |||||||||
| 5 | % SS is the percent soluble solids of fresh berries. | |||||||||
| 6 | Disease ratings are on a 0 to 5 scale: 0 = no disease seen, 5 = 100% of plants have disease present. | |||||||||
| Table 5. 2002 thornless blackberry cultivar evaluation. | ||||||||||
| Cultivar/Selection* | Harvest Start1 | Harvest Days2 | Pounds Fruit/A | Fruit Size (oz) | Taste3 | Appearance4 | % SS5 | Disease Rating6 | Remarks | |
| Triple Crown | 7/06 | 28 | 7623 A | 0.193 A | S | A | 10.0 | 0 | ||
| A1689 | 6/30 | 37 | 4793 B | 0.188 B | S | A | 9.3 | 0 | ||
| Ouachita (A1905) | 6/24 | 41 | 3472 BC | 0.183 C | S | A+ | 10.2 | 0 | ||
| A1963 | 6/26 | 33 | 2165 CD | 0.178 D | S | A+ | 8.3 | 0 | ||
| A1960 | 6/23 | 40 | 2103 CD | 0.166 E | S | A+ | 9.9 | 0 | ||
| A1539 | 6/19 | 43 | 1873 DE | 0.164 E | T | A+ | 9.2 | 0 | ||
| A1857 | 6/20 | 26 | 801 DEF | 0.134 F | ST | A | 10.9 | 0 | uneven drupelets | |
| Navaho | 6/26 | 23 | 537 EF | 0.010 H | ST | A- | 8.8 | 0 | uneven drupelets | |
| A2049 | 6/21 | 28 | 452 F | 0.119 G | ST | A- | 10.5 | 0 | ||
| LSD 5% | 1369 | 0.004 | ||||||||
| * | Entries or selections preceded by an “A” and followed by a number are unreleased breeding selections and are not available commercially at the time of this testing and reporting. LSD 5% Least significant difference at the 5% level. | |||||||||
| 1 | The first day of harvest for that cultivar. | |||||||||
| 2 | The number of days between first and last harvest for each cultivar. | |||||||||
| 3 | Taste of fresh fruit: T = tart, S = sweet, B = bland. | |||||||||
| 4 | Appearance: A- = below average, A = average, A+ = above average. | |||||||||
| 5 | % SS is the percent soluble solids of fresh berries. | |||||||||
| 6 | Disease ratings are on a 0 to 5 scale: 0 = no disease seen, 5 = 100% of plants have disease present. | |||||||||
| Table 6. 2003 blackberry cultivar evaluation. | |||||
| Cultivar/Selection* | Pounds Fruit/A | Fruit Size (oz) | Taste1 | Appearance2 | |
| A1963 | 2843.7 | 0.175 | S | A | |
| A1539 | 6178.3 | 0.189 | S | A | |
| A2049 | 703.3 | 0.19 | ST | A- | |
| A1857 | 4945.9 | 0.159 | ST | A | |
| A1854 | 3908.6 | 0.122 | ST | A | |
| A1960 | 2242 | 0.151 | ST | A | |
| A1689 | 5552.1 | 0.212 | S | A | |
| Ouachita (A1905) | 6366.1 | 0.173 | ST | A | |
| Navaho | 1577.2 | 0.087 | ST | A | |
| Kiowa | 4165.4 | 0.312 | ST | A+ | |
| Shawnee | 7123 | 0.118 | ST | A+ | |
| Triple Crown | 8581.8 | 0.122 | S | A+ | |
| LSD 5% | |||||
| * | Entries or selections preceded by an “A” and followed by a number are unreleased breeding selections and are not available commercially at the time of this testing and reporting. LSD 5% Least significant difference at the 5% level. | ||||
| 1 | Taste of fresh fruit: T = tart, S = sweet, B = bland. | ||||
| 2 | Appearance: A- = below average, A = average, A+ = above average. | ||||
Douglas Archbold, J. Matthew Fulkerson, and Valeria Sigal Escalada, Department of Horticulture
Blackberry fruits have a short shelf life, and some quality loss can occur under recommended refrigerated storage conditions. Blackberry growers in Kentucky have indicated some preference for fiber baskets over plastic clamshell containers for marketing the berries, although the latter type of container is most common in the major retail chains. Shelf life of blackberries in the fiber baskets has not been directly compared to that in the clamshell containers, although more water loss from berries in the open basket may be expected, which could affect their quality and appearance. Modified atmosphere (MA) storage, raising CO2 and/or lowering O2 from ambient levels, has become common postharvest practice for extending shelf life of many perishable crops such as blackberries, and simple, cost-effective techniques for MA use are commercially available regardless of the scale of production. Although blackberries grown on the West Coast are commonly stored and shipped under MA conditions, the response of eastern thornless blackberries to MA storage has not been reported. The objectives of this work were to study 1) the influence of storage container type on blackberry fresh weight during postharvest storage and 2) the response of Chester thornless blackberry to MA conditions in refrigerated storage.
Chester thornless blackberries were harvested once a week for four weeks from the thornless blackberry planting at the University of Kentucky Horticulture Farm. Six fiber baskets and six plastic clamshells, each with 150 to 200 g of fruit, were prepared and weighed on each harvest date. The containers were placed in 2°C storage, and after a week were removed, weighed again, and set at room temperature. They were reweighed again after three days.
For MA studies, quality of a sub-sample of 12 to 15 berries was measured as described below on each harvest date, and 150 to 200 g of fruit were placed into plastic bags and weighed. The open bags were set into 1-liter Mason jars. To incorporate a modified atmosphere into each jar, the lids were loosely placed on each jar, and a needle was inserted through a septum in the lid to inject the MA. Then, 20% CO2 or 5% O2, with the other gases at ambient levels, was flushed through each bottle for approximately 30 seconds. After this application, the needle was removed and the lid was sealed. Control jars of ambient air were sealed shut without flushing. The containers were stored at 2°C. After seven days, the jars were removed from cold storage, and the quality of the fruit in half the jars of each treatment was measured. The bags of fruit were removed from the remaining jars and were set open in clamshell containers at ambient temperature for three days, at which time fruit quality parameters were measured. There were at least three containers per MA treatment per harvest date analyzed at seven and 10 days after harvest.
Quality traits of individual fruit measured included color using a Minolta Chroma Meter Model CR-200 and firmness using a Chatillon Force Gauge. A harvest date mean and a jar/container mean for color and firmness values were derived from the data. Data were analyzed by analysis of variance (ANOVA).
In cold storage, the fruit in the fiber baskets lost significantly more fresh weight than those in the clamshell containers (8.5% versus 6.3%). During the post-cold storage three-day period at room temperature, berries in the fiber baskets also lost significantly more fresh weight (15.1% versus 10.6% in the clamshell containers). Thus, fiber baskets may work well for immediate marketing of blackberries, but they are inferior to clamshells if a period of cold storage precedes marketing.
Neither modified atmosphere treatment affected the postharvest quality of Chester blackberries during or after cold storage. Fruit firmness increased slightly, less than 10%, during cold storage and decreased about 25% during the subsequent three days at room temperature. Fruit color somewhat intensified during postharvest storage. The blackberries tolerated the MA conditions with no obvious adverse effects even though they were in the upper range of conditions that are commercially used, but there was no obvious benefit to the use of MA. It remains to be determined if other eastern thornless blackberry cultivars will respond comparably.
John Hartman, Chris Smigell, R. Terry Jones, Paul Bachi, Julie Beale, April Satanek, and John Strang, Departments of Plant Pathology and Horticulture
Blackberries in Kentucky are subject to several serious diseases. Some of these diseases are present in native blackberries growing in the wild and represent a threat to domestic blackberries growing nearby. In addition, some diseases may be endemic to certain regions of Kentucky due to unique weather or topography.
Orange rust. This disease affects both blackberry and black raspberry and can often be seen in native or naturalized wild plantings. In Kentucky, orange rust is caused by the fungus Gymnoconia nitens, but the fungus Arthuriomyces peckianus, causing identical symptoms, may also be involved. Orange rust is the most important of several rusts of blackberry. Infected plants can be easily identified shortly after growth appears in spring when newly formed shoots appear weak and spindly. The new expanding leaves on such canes are stunted or misshapen and pale green to yellowish. The leaf edges may have a bronze color. The lower leaf surfaces of these infected shoots bear tiny orange pustules, visible with a hand lens. In a few weeks, the lower surface of infected fully expanded leaves are covered with highly visible waxy, bright orange blister-like pustules. Spores from these pustules, when blown to nearby healthy plants, will initiate new infections. Diseased blackberries become infected systemically, even below ground, and will bear little or no fruit.
Rosette. Also called "double blossom," rosette disease, caused by the fungus Cercosporella rubi, mainly affects blackberries, and only rarely raspberries or black raspberries. First symptoms are flowers with distorted petals, giving the appearance of a double flower (hence double blossom). The mycelium of the fungus grows over the flower pistils and stamens, producing a whitish spore mass. Unopened flowers are usually elongated and larger, coarser, and redder than normal. Sepals on infected flowers enlarge and occasionally become leaf-like. On some varieties, shoots may appear abnormal with leafy proliferation (rosette) or witches'-broom. Berries do not develop from infected branches, and other parts of the cane may produce only small, poor quality fruit.
For both of these diseases, blackberries can become infected from fungal spores produced on wild blackberries nearby. Therefore, it is important to remove and destroy infected blackberry plants as they occur in the field and also wild blackberries and other brambles near the planting.
The objective of this study was to begin a survey of blackberry plantings and native blackberry patches in Kentucky for presence of orange rust and rosette diseases.
Selected and representative commercial blackberry plantings and wild brambles statewide were surveyed as opportunities occurred on field visits by Extension personnel during the 2003 growing season. Blackberries were examined for symptoms and signs of orange rust disease and for symptoms of rosette disease. Samples of plants showing symptoms of either disease were collected and disease identifications were verified microscopically as needed in the University of Kentucky Plant Pathology Department Plant Disease Diagnostic Laboratory.
Archived UK Plant Disease Diagnostic Laboratory databases were searched for county records of blackberry orange rust and rosette diseases. Data from 1983-1992 and 1993-2002 were searched and recorded.
During the past 20 years, blackberry orange rust has been observed in 30 Kentucky counties (Table 1, Figure 1). The disease appears to be distributed throughout the state wherever blackberries are grown. Western, central, and eastern regions of Kentucky are equally represented in the survey. The survey this year doubled the number of counties reporting orange rust compared to grower and county agent sampling during the previous 20 years. This suggests that the true extent of orange rust in Kentucky will only be found with a dedicated survey for the disease or that orange rust disease has not been noticed by or caused much concern for growers in the past.
Blackberry rosette is found in 16 counties, and it also appears to be distributed within each region of the state (Table 2, Figure 2). However, it appears that 11 to 20 years ago the disease was more commonly noticed or caused concern in Western Kentucky, one to 10 years ago in Central Kentucky, and now is being more commonly noticed in Eastern Kentucky. Again, the survey in one year added significantly to the total number of counties recording rosette disease.
Records of the two diseases in this survey are likely biased toward counties where commercial blackberries are grown; this is where Extension personnel would make most of their investigations. Based on disease distribution revealed in this survey, it should be assumed that blackberry orange rust and rosette diseases can occur statewide. Kentucky blackberry growers will want to know where these diseases are a threat so that they can be alert to the need for eradication of wild plantings nearby and for the need to apply appropriate and timely controls on their blackberry crops.
| Table 1. Kentucky counties with records of blackberry orange rust disease. | |||
| 1983-1992 Laboratory Data | 1993-2002 Laboratory Data | 2003 Survey | |
| Bourbon | Daviess | Barren | |
| Crittenden | Fayette | Bell | |
| Logan | Graves | Bracken | |
| Madison | Jackson | Bourbon* | |
| Morgan | Marion | Breathitt | |
| Todd | Muhlenberg | Carter | |
| Warren | Shelby | Daviess* | |
| Woodford | Fayette* | ||
| Fleming | |||
| Garrard | |||
| LaRue | |||
| Mason | |||
| Nicholas | |||
| Jackson* | |||
| Owen | |||
| Powell | |||
| Robertson | |||
| Scott | |||
| Simpson | |||
| Woodford* | |||
| * | Previously reported. | ||
| Table 2. Kentucky counties with records of blackberry rosette disease. | |||
| 1983-1992 Laboratory Data | 1993-2002 Laboratory Data | 2003 Survey | |
| Caldwell | Bourbon | Breathitt | |
| Harlan | Fayette | Laurel | |
| Livingston | Kenton | Whitley | |
| McCracken | Madison | Woodford* | |
| Washington | Owen | ||
| Pulaski | |||
| Taylor | |||
| Woodford | |||
| * | Previously reported. | ||
HORTICULTURAL CROPS—GREENHOUSE CROPS
J.W. Buxton and J.A. Pfeiffer, Department of Horticulture
Improper irrigation significantly limits the growth, quality, and profit of commercial container-grown crops. Generally crops are either irrigated too frequently or more likely insufficiently irrigated, especially under bright, warm conditions. Also, most crops are not irrigated uniformly. The objective of this study was to develop an automatic, no-runoff irrigation system that controls and maintains a uniform water/air ratio in the growing media of all containers in a growing area.
The Controlled Water Table (CWT) irrigation system is a modification of capillary mat irrigation used extensively in commercial greenhouses (Figure 1). The vertical placement of the water surface in the trough below the bench determines the air/water ratio in the container growing medium. With the water surface at bench level (0 CWT), the medium holds the maximum amount of water. Lowering the water surface in the trough below the bench decreases the water content and increases the air content in the growing medium. CWT has been used to grow many commercial greenhouse crops in various container sizes (2,3,4,5). Geranium studies are discussed in this report.
Rooted geranium cuttings were planted in a 15-cm plastic container containing a peat-based growing medium. Peter's Peatlite fertilizer (15N-7P-14K) at the rate of 100 mg N per liter with proportional amounts of other elements as indicated by the fertilizer analysis was used as the fertilizer source. The six plants of each treatment were spaced on 30.5 cm centers in a randomized complete block design with three replications. At the conclusion of the research, geranium tops were cut off at the medium surface, and leaf area and plant dry weight were determined. Data for leaf area are presented here.
At constant CWT, the medium air exchange occurs very slowly; therefore, CO2, ethylene, and other gasses accumulate and may become toxic, and O2 concentration is lowered (1,6). In fluctuating CWT studies, the level of the water surface goes up and down between the two distances below the bench surface. When the water in the trough moves from the high to the low level, the amount of moisture in the growing medium decreases and the amount of air increases. Also, the possible toxic gases in the medium will be flushed out when the water rises, and fresh air is moved into the medium when the water goes down.
Constant CWT. Geraniums in 15-cm containers were grown with the CWT set at 0, 2, 4, and 6 cm (Figure 2). Plant growth at CWT 0 and 2 cm was significantly larger than that of those grown at CWT 4 and 6 cm. Roots of plants grown at CWT 0 cm grew mostly in the middle of the container and few reached the bottom, indicating that the water content was too great and the air content too low near the bottom. However, roots of plants at CWT 2 cm were distributed uniformly from the center to the bottom of the container.
Fluctuating CWT and Day/Night Regulation. A day/night regulation of a fluctuating CWT was compared with the constant CWT. The treatments were CWT 2 cm day (D) and night (N), CWT 2 cm D, 2-4 cm D and N, and 2-4 cm D. In the CWT 2-4 cm treatments, the nutrient solution fluctuated between 2 cm and 4 cm. The CWT table was turned off at 7 p.m. and came on at 7 a.m. The control for the fluctuating system is shown in Figure 3. The CWT treatments did not significantly affect geranium leaf area or dry weight (Figure 4). Alternating the CWT between 2 and 4 cm appears to have some benefit, and turning the system off at night seems to reduce growth in both the constant and fluctuating CWT compared to being on continuously. However, the variability within the study was large, and additional studies are needed to confirm results.
Fluctuating CWT. In this study the treatments were CWT 2 cm, CWT 2-3 cm, CWT 2-4 cm, and CWT 1-4 cm. The leaf area of plants grown at a constant CWT of 2 cm, 2-3 cm, and 2-4 cm treatments had the same leaf area. However, plants grown at 1-4 cm were significantly smaller than the plants in the other treatments (Figure 5). Apparently, dropping the water table to 4 cm below the bench, even for a short time, reduces growth. Plants grown in constant CWT 4 cm in the previous discussion above also grew poorly (Figure 2).
Plant placement from trough. The first plant in each treatment is 15 cm from the trough, whereas the sixth pot is 165 cm from the trough. While young plants grow at the same rate, as plants became larger, the first pot was larger than the sixth pot (Figure 6). At the end of the experiment, samples of water from the mat were analyzed for N, P, K, Ca, Mg, Zn, Cu, Fe, and Mn. Only the data for N and Fe are shown (Figures 7a and 7b). The amount of N, K, P, Ca, Mg, and Mn in the mat decreased from position 1 to 5, whereas the amount of Fe increased the greater the distance from the trough. Zn and Cu remained nearly constant. In general, the amount of each nutrient at position 6 was greater than at position 5. The evaporation of water from the mat edge at position 6 probably concentrated the nutrients. The data suggest the first pot removes more nutrients, such as N, relative to the water uptake, and the next pots in the row receive decreased concentration of some nutrients the greater the distance from the trough. Future work will identify the nutrient concentration needed at different stages in development.
A CWT irrigation system is adaptable for the production of many container-grown plants and provides several advantages over other irrigation systems.
Other advantages include:
Robert G. Anderson, Department of Horticulture
The cut flower market in the United States remains strong. Rose sales are up; more than 1.22 billion rose stems were sold in the United States in 1998, and per capita consumption has doubled in the last 20 years (6). Unfortunately, U.S. production has not only lost a significant portion of domestic share but has failed to expand with the global market. For roses, the percentage of domestic sales from imports in 1975, 1981, 1988, and 1992 ranged from 1%, 15%, 34%, and 52% respectively, and was 78% in 1998 (6). U.S. production has decreased only 40% in the last 10 years, but the market continues to expand with product from overseas.
The primary market periods are three major U.S. holidaysValentine's Day, Mother's Day, and Christmas. In order to have flowers for these peak market periods, the plants must be maintained year-round in controlled environment greenhouses. Hybrid tea roses are unusual, because they flower continuously throughout the year. Thus, each rose plant must be visited by a worker once or twice a day, every day of the year, for flower harvest. Consequently, production costs are quite high, because labor must be used to harvest flowers every day of the year and thus to try to sell the flowers throughout the year, even when market demand is low. Of course, all other overhead and energy costs must be maintained for the calendar year as well. The primary market periods are certainly an important target, however. Valentine's Day prices of $1.10 to $2.25 per rose stem in the Chicago market compare favorably with the year-round average of $0.33 (1).
Cheap labor overseas has been a main factor in the loss of U.S. rose production. Traditional methods of rose production (15,8) practiced in the United States, and now overseas, are labor intensive and monotonous, thus utilizing large numbers of unskilled, low-wage employees. While low production costs overseas were the main factor in the loss of this industry, current environmental laws and the nation's need for sustainable agricultural production systems that reduce the energy input per product and that increase the wages for individual employees are also important.
Greenhouses in Kentucky and the United States did not disappear with the change in the rose market; these businesses simply adapted to other markets and crops. The bedding plant industry that produces flowers for home and commercial landscapes has increased dramatically in the last 20 years. As the greenhouse industry changed, plant production technology changed as well. Ebb-flood irrigation, palletized benches, plug technology, and robotic transplanters have changed greenhouses (10). Greenhouse operators that have invested in new labor-efficient equipment are looking for new crops to pay for their investments.
An alternative to conventional rose production is to grow roses for only six months of the year. This production schedule would allow roses to be grown as part of the currently successful bedding plant business. Roses could be grown from cuttings started in August just as poinsettias are potted. Roses would compete with garden mums and poinsettias for greenhouse space in the summer and fall, but both crops have saturated their markets and prices have not increased in a number of years. After cut stems are harvested for Christmas and Valentine's Day, the plants can be discarded. This six-month alternative is well supported by an economic evaluation of single stem roses (5). An unusually high internal rate of return (175%) was estimated for Valentine's Day rose production integrated into a typical greenhouse system that produced bedding plants, garden mums, and poinsettias.
Roses can be grown from cuttings quite easily. Rose growers have used cuttings for the last 100 years as part of their production system, and all miniature roses for pots are propagated from cuttings (14). Cuttings have been used to produce roses for many university experiments (7,12,11,16). Evaluation of single node cuttings for cut rose production was begun in the late 1980s (2,17,13). In general, typical propagation systems, intermittent mist, bottom heat at 70° to 75°F, and application of rooting hormone work well. Anderson (3,4) proposed the use of single node rose cuttings as the source of plants for a mechanized cut flower production system.
1. Develop a production model to produce roses from cuttings for Christmas and Valentine's Day.
Roses are relatively easy to grow from cuttings. Flowering stems were harvested for cuttings on Aug. 16 and 29 and on Sept. 9 and 12, 2002. Cut rose stems were cut into 4- to 5-cm segments, each segment having a single leaf and bud. The lower 1 cm of each cutting received a 5-sec. dip in a solution of 750 ppm IBA in 50% ethanol. Cuttings were placed into a 6-cm pot containing a commercial growing medium. The cuttings were placed under intermittent mist, and the rooting media temperature maintained at 75°F.
Approximately 750 rooted cuttings from 14 red rose cultivars were transplanted into MetroMix 560 growing medium in 6-inch pots on Sept. 28 and on Oct. 22 and 27. Plants were placed pot to pot in a greenhouse that received ambient light levels. Greenhouse temperatures were maintained at an average daily temperature of 60°F during the fall and winter. Plants were irrigated by hand with a fertilizer solution, Peter's 20-10-20, with an EC of 1.0 to 1.2 dS and pH of 5.5 to 6.5 each day.
Pruning practices were compared during the winter of 2002-2003. Plants were pruned to 5 inches or 12 inches on Dec. 2 and compared with unpruned plants that were tied together in groups of four plants. The tying technique allowed light to reach the lower parts of the plant where new shoots could emerge.
2. Prepare economic simulations of the model that focus on production costs for alternative plant densities, containers, and pruning systems.
It is relatively simple to compare the yield of cut rose stems with sample production costs. Commercial greenhouses have an operating cost of approximately $0.25 per square foot per week (Will Southerland, 2002, personal communication). Rose plants transplanted in mid-October will use greenhouse space for 16 weeks if roses are harvested for Valentine's Day. Cut rose production, in this system, costs $4.00 per square foot of space used. The plants were planted into 6-inch pots, so there are four plants per square foot of space. Thus, the returns need to be at least $1.00 per plant. At prices of $1.00 or more per cut stem, this system needs to produce at least one high-quality stem per plant.
3. Validate the optimal economic model by growing the roses in the greenhouse in replicated studies.
Rose growth is directly related to the amount of light the plants receive. The winter of 2002-2003 had unusually low light levels, so overall rose performance was poor. All cultivars of roses pruned to a 5-inch height in early December had a yield of less than one stem per plant. `Olympiad' and `Cesar Chavez' roses produced 1.5 and 1.2 stems per plant in the 12-inch and tied treatments.
4. Evaluate cultivars of red roses for their performance in a short-term production system.
Modern red greenhouse rose varieties, `Black Magic' and `Fahrenheit'; traditional red greenhouse rose varieties, `Samantha' and `Taboo'; modern garden roses, `Cesar Chavez', `Burning Desire', `Opening Night', `Veteran's Honor', `Crimson Bouquet', and `Cardinal's Song'; and traditional red garden roses, `Olympiad' and `Ingrid Bergman', were evaluated in this study. `Black Magic', `Olympiad', `Cesar Chavez', and `Kardinal' will be used in 2003-2004 studies.
Robert G. Anderson, Department of Horticulture, and Master Gardeners from McCracken, Warren, Hardin, Pulaski, Jefferson, Fayette, Boone and Campbell Counties
Annual and perennial garden flowers have been evaluated for many years at the University of Kentucky. Trials have occurred at the University of Kentucky Arboretum since 1993. These trials were expanded at the Horticulture Research Farm in 1999 and 2000 with grants from the Kentucky Department of Agriculture, the Kentuckiana Greenhouse Association, and the New Crop Opportunities Center.
Demonstration gardens have been established at eight locations across the state. We wish to thank the Extension agents and Master Gardeners at these garden locations for planting, maintaining, and evaluating the annual flowers in these trials.
Selected annual flowers were grown in Lexington and distributed to the demonstration gardens in May. The Master Gardeners and Extension agents planted the flowers in their trial gardens and evaluated them four times during the summer (mid-July, early August, late August, mid-September). All gardens were mulched with wood chip mulch; drip irrigation was used throughout the summer, and plants were fertilized during the summer. Plant performance (Table 1) was evaluated on a 1 to 5 scale with 1 = poor and 5 = excellent. The evaluation was based only on the individual gardener's determination of the quality of the plants. Although personal tastes are reflected in individual evaluations, the overall evaluation was accurate for the plant performance in each garden. The demonstration gardens seem to be a good educational activity for the Master Garden educational program. It is the goal of this program to allow Master Gardeners to see new flowers and compare them to the reliable annual flowers seen in Kentucky gardens.
Photos and details about plant performance are continually added to the Kentucky Garden Flowers Web site: <http://www.uky.edu/Ag/Horticulture/gardenflowers>. Also, going to the University of Kentucky home page <www.uky.edu> and searching for a plant will direct the reader to the Kentucky Garden Flowers location.
| Table 1. Evaluations of annual flowers, 2002. | ||
| Variety | Scientific Name | Rating* |
| Spreading Petunia—‘Wave Pink Improved’ | Petunia x hybrida | 4.7 |
| Lantana—‘Miss Huff’ | Lantana camara | 4.6 |
| Mealy Cup Sage—‘Victoria’ | Salvia farinacea | 4.5 |
| Vinca—‘Big Ruby’ | Catharanthus roseus | 4.5 |
| Lantana—‘Samantha’ | Lantana camara | 4.4 |
| Lantana—‘Patriot Sunburst’ | Lantana camara | 4.4 |
| Summer Snapdragon—‘AngelMist Purple’ | Angelonia angustifolia | 4.3 |
| Lantana—‘Patriot Cherry’ | Lantana camara | 4.3 |
| Lantana—‘Patriot Hot Country’ | Lantana camara | 4.3 |
| Summer Snapdragon—‘AngelMist Pink’ | Angelonia angustifolia | 4.3 |
| Summer Snapdragon—‘AngelMist Purple Stripe’ | Angelonia angustifolia | 4.3 |
| Summer Snapdragon—‘AngelMist Lavender’ | Angelonia angustifolia | 4.3 |
| Lantana—‘Weeping Lavender’ | Lantana camara | 4.3 |
| Narrow Leaf Zinnia—‘Crystal White’ | Zinnia angustifolia | 4.2 |
| Lantana—‘Patriot Hallelujah’ | Lantana camara | 4.2 |
| Spreading Petunia—‘Easy Wave Shell Pink’ | Petunia x hybrida | 4.1 |
| Spreading Petunia—‘Wave Blue’ | Petunia x hybrida | 4.0 |
| Summer Snapdragon—‘AngelMist White’ | Angelonia angustifolia | 3.9 |
| French Marigold—‘Aspen Red’ | Tagetes patula | 3.8 |
| Lantana—‘Patriot Cowboy’ | Lantana camara | 3.8 |
| Lantana—‘Patriot Desert Sunset’ | Lantana camara | 3.8 |
| Lantana—‘Patriot Dove Wings’ | Lantana camara | 3.8 |
| Tooth Ache Plant—‘Peek a Boo’ | Acmella (Spilanthes) oleracea | 3.7 |
| Polka Dot Plant—‘Rose Splash Select’ | Hypoestes phyllostachya | 3.7 |
| Summer Snapdragon—‘AngelMist Deep Plum’ | Angelonia angustifolia | 3.6 |
| Spreading Petunia—‘Easy Wave Cherry’ | Petunia x hybrida | 3.4 |
| Spider Flower—‘Sparkler White’ | Cleome hassleriana | 3.4 |
| Brazilian Snapdragon | Otacanthus azureus | 3.3 |
| Spider Flower—‘Sparkler Blush’ | Cleome hassleriana | 3.2 |
| Spider Flower—‘Sparkler Rose’ | Cleome hassleriana | 3.1 |
| Globe Amaranth—‘Gnome Mix’ | Gomphrena globosa | 3.0 |
| Cupflower—‘Summer Splash Blue’ | Nierembergia hippomanica | 2.8 |
| Spider Flower—‘Sparkler Lavender’ | Cleome hassleriana | 2.7 |
| Wishbone Flower—‘Summer Wave Blue’ | Torenia fournieri | 2.6 |
| Cupflower—‘Summer Splash White’ | Nierembergia hippomanica | 2.5 |
| Flowering Tobacco—‘Avalon Mix’ | Nicotiana x sanderae | 2.5 |
| Flowering Tobacco—‘Heaven Scent Mix’ | Nicotiana x sanderae | 2.4 |
| Flowering Tobacco—‘Domino Mix’ | Nicotiana x sanderae | 2.2 |
| Flowering Tobacco—‘Saratoga Mix’ | Nicotiana x sanderae | 1.9 |
| Flowering Tobacco—‘Havana Appleblossom’ | Nicotiana x sanderae | 1.8 |
| * Rating of 1 to 5 with 1 = poor and 5 = excellent. | ||
Robert G. Anderson and Kirk Ranta, Department of Horticulture
Annual and perennial garden flowers have been evaluated for many years at the University of Kentucky. Trials have occurred at the University of Kentucky Arboretum since 1993. These trials were expanded at the Horticulture Research Farm in 1999 and 2000 with grants from the Kentucky Department of Agriculture and the Kentuckiana Greenhouse Association. Grants from the New Crop Opportunities Center allowed expansion of the trials to more than 20,000 square feet of trial gardens in Lexington. Additionally, demonstration gardens have been established at eight locations across the state (listed below).
The collection of perennials in our ongoing trials continues to expand. We have nearly 1,000 individual plants in the perennial trials, with more than 150 species and cultivars in the plots at the Horticulture Research Farm in Lexington. Our trials include the Perennial Plants of the Year from the Perennial Plant Association and some native plants. We now have three years' experience with some, so our ratings have many observations. However, our ratings should be used only as a guide to determine which perennials you might sell or use in Kentucky landscapes. In general, those that have grown well for two or more seasons are marked (++), and those that have not done too well are marked (-); those unmarked need more time to determine a rating.
Photos and details about plant performance are continually added to the Kentucky Garden Flowers Web site: <www.uky.edu/Ag/Horticulture/gardenflowers>. Also, going to the University of Kentucky home page <www.uky.edu> and searching for a plant will direct the reader to the Kentucky Garden Flowers location.
Agastache `Tutti Frutti' (`01-`02) ( - )
Amsonia hubrectii (`01-`02) (+)
Artemisia absinthium `Huntington Gardens' (`01) ( - )
Aster apellus `Triumph' (`00-`02) (-), Aster laevis `Bluebird' (`00-`02) (++), Aster latiflorus `Prince' (`00-`02), Aster novi-belgii `Celeste' (`01-`02), Aster novi-belgii `Purple Monarch' (`01-`02), Aster novi-belgii `Snow Cushion' (`00-`02), Aster novi-belgii `White Swan' (`00-`02) (++), Aster novi-belgii `Winston Churchill' (`01-`02), Aster novi-belgii `Woods Purple' (`00-`02), Aster x frikarti `Monch' (`00-`02), Aster oblongifolius `Raydon's Favorite' (`02), Kalimeris mongolica (`01-`02) (++), Kalimeris mongolica `Variegata' (`00-`02) (++)
Astilbe `Sprite' (`00-`02) (++)
Aquilegia x hybrida `Rose w/White Edge' (`02), `Songbird Cardinal' (`02), `Winky Red & White' (`02)
Baptisia pendula (`01-`02)
Buphthalum salicifolium `Sun Wheels' (`00-`02) ( - )
Bellis perennis `Galaxy Rose' (`02), `Rose Border' (`02), `Tasso Strawberry & Cream' (`02)
Calamagrostis acutifolia `Karl Foerster' (`00-`02) (++), Calamagrostis acutifolia `Overdam', (`02), Variegated Feather Reed Grass, Calamagrostis brachytricha, (`02), Korean Feather Reed Grass
Chasmanthium latifolium (++) (`00-`02)
Ajania pacificum `Pink Ice' (++) (`00-`02), Chrysanthemum `Hillside Pink' (`01-`02), Chrysanthemum yezoense (`00-`02), Dendranthema rubellum `Clara Curtis' (`00-`02), Dendranthema rubellum `Mary Stoker' (`00-`02)
Chrysanthemum (Leucanthemum) x superbum `Becky' (`02)
Conradina verticillata
Coreopsis `Tequila Sunrise' (`01-`02), Coreopsis grandiflora `Domino' (`02), Coreopsis grandiflora ` Early Sunrise' (`02), Coreopsis lanceolata `Baby Sun' (`02)—Lanceleaf Coreopsis Coreopsis rosea `American Dream' (`01-`02), Coreopsis verticillata `Moonbeam' (`00-`02) (++)
Crocosmia crocosmiifolia `Venus' (`00-`02)
Dianthus allwoodii `Doris' (`02)—Allwood Pink, Dianthus allwoodii `Frosty Fire' (`02)—Allwood Pink, Dianthus deltoides `Brilliant' (`01-`02)—Maiden Pink, Dianthus gratianopolitanus `Bath's Pink' (`02) (++)—Cheddar Pink
Echinacea pallida (`00-`02), Echinacea paradoxa (`00-`02), Echinacea purpurea (`00-`02) (++), Echinacea purpurea `Magnus' (`00-`02) (++), Echinacea simulata (`00-`02), Echinacea tennesseensis (`00-`02) (++)
Erianthus alopecuroides (`00-`02)
Erigeron `Azure Fairy' (`00-`02) ( - )
Eupatorium coelestinum (`01-`02) (++)
Eupatorium maculatum (`00-`02) (++), Eupatorium maculatum `Carin' (`02), Eupatorium maculatum `Gateway' (`02)
Fuchsia magellanica `Ricartonii' (`02) ( - )
Gaura lindheimeri `Siskiyou Pink' (`01-`02)
Geranium `Dusky Rose' (`00-`02), Geranium cantabrigiense `Blokova' (`00-`02), Geranium cantabrigiense `Karmina' (`00-`02), Geranium cinereum `Ballerina' (`00-`02), Geranium clarkei `Kasmir Purple' (`00-`02), Geranium maculata `Claridge Druce' (`00-`02), Geranium phaeum `Samobor' (`00-`02)
Helenium `Coppella' (+) (`00-`02)
Helianthemum `Annabel' (`01-`02) (++), Helianthemum nummularium `Double Red' (`01-`02)
Helianthus angustifolius `Gold Lace' (`02), Swamp Sunflower, Helianthus mollis (`00-`02)—Downy Sunflower, Heliopsis `Loraine Sunshine' (`00-`02) (++)—False Sunflower
Hemerocallis `Stella d'Oro' (`01-`02) (++)
Heuchera x brizoides `Bressingham Hybrid' (`01-`02), Heuchera micrantha `Palace Purple' (++) (`00-`02)
Hibiscus moscheutos `Disco Bell Pink' (`00-`02) (++), `Disco White' (`00-`02) (++), `Kilimanjaro Red' (`01-`02) (++), `Ranier Red' (`01-`02) (++), `Mauna Kea' (`01-`02) (++), `Etna Pink' (`01-`02) (++), `Matterhorn' (`01-`02) (++)
Lagerstroemia indica `Supersonic Mix' (`02)
Limonium latifolia (`00-`02)
Lobelia speciosa `Fan Burgundy' (`01-`02)
Lychnis coronaria `Angel Blush' (`01-`02), Lychnis flos-jovis nana `Peggy' (`01-`02) ( - )
Marshallia grandiflora (`02)—Barbara's buttons, Marshallia mohrrii (`02)
Miscanthus sinensis `Morning Light' (`01-`02) (++)
Monarda didyma `Fireball' (`02)—Petite Bee Balm, `Jacob Cline' (`01-`02), `Marshall's Delight' (`01-`02), `Pink Supreme' (`02)—Petite Bee Balm
Calamintha nepeta `White Cloud' (`02)—Savory Calamint, Nepeta `Dawn to Dusk' (`00-`02) (++), Nepeta `Subsessilis' (`00-`02) (++), Nepeta faassenii `Six Hills Giant' (`00-`02) (++), `Walker's Low' (`02)
Origanum laevigatum `Herrenhausen' (`01-`02) (++)
Parthenium integrifolium (`00-`02) (++)
Pennisetum alopecuroides `Hameln' (`01-`02) (++)
Penstemon barbatus `Prairie Dusk' (`01-`02), Penstemon digitalis `Husker Red' (`00-`02) (++), Penstemon fruticosa `Purple Haze' (`01-`02)
Perovskia atriplicifolia (`00-`02) (++), `Little Spire' (`02)
Persicaria amplexicaule `Firetail' (`01-`02), Persicaria bistorta `Superbum' (`01-`02)
Phlox maculata `Miss Lingard' (`00-`02) (++), `Natasha' (`00-`02) (++)
Phlox paniculata `David' (`02), `Jill' (`02), `Margie' (`02), `Nicky' (`02), `Robert Poore' (`02), Phlox pilosa `Eco Happy Traveller' (`02)—Downy Phlox
Ratidiba columnifera `Mexican Hat' (`00-`02) (++)
Rudbeckia fulgida var. sullivanti `Goldsturm' (`00-`02) (++)—Cone Flower, Rudbeckia fulgida var. fulgida (`02)—Cone Flower, Rudbeckia hirta (`02)—Black Eye Susan, `Autumn Colors' (`02), `Cordoba' (`02), `Goldilocks' (`02), `Indian Summer' (`02), `Prairie Sun' (`02), `Sonora' (`02), `Toto Gold' (`02), `Toto Lemon' (`02), `Toto Rustic' (`02), Rudbeckia laciniata `Herbstonne' (`02)—Cutleaf Cone Flower, Rudbeckia occidentalis (`02) `Black Beauty', Rudbeckia subtomentosa (`00-`02) (++)—Sweet Black Eye Susan, Rudbeckia triloba (`00-`02) (++)—Brown Eye Susan
Salvia `Blue Hill' (`00-`02) (+), `Blue Queen' (`00-`02) (+), `May Night' (`00-`02) (++), `Blue Hill' (`00-`02) (+), `Snow Hill' (`00-`02) (+), Salvia lyrata `Burgundy Bliss' (`00-`02) ( - )
Scabiosa caucasica `Perfecta Alba' (`00-`02), Scabiosa columbaria `Butterfly Blue' (`00-`02), `Pink Mist (+)' (`00-`02)
Schizostylis coccinea (`00-`02)
Sedum spectabile `Autumn Joy' (`00-`02) (++), `Brilliant' (`00-`02), `Stardust' (`02), Sedum spurium `Vera Jameson' (`00-`02) (++)
Solidago rugosa `Fireworks' (`02)
Spirea latifolia (`00-`02) (++)
Sporobolis heterolepis (`02)
Stokesia laevis `Blue Danube' (`00-`02) (-), `Klaus Jellito' (`00-`02), `Mary Gregory' (`00-`02) (-), `Omega Skyrocket' (`02), `Purple Parasols' (`00-`02), `Silver Moon' (-) (`00-`02)
Verbascum `Helen Johnson' (`00-`02), Verbascum `Jackie' (`00-`02)
Veronica `Fascination' (`00-`02), Veronica `Giles van Hess' (`00-`02), Veronica `Goodness Grows' (`00-`02), Veronica `Spring Dew', Veronica `Waterperry' (`01-`02), Veronica `White Jolanda' (`00-`02) (++), Veronica alpinia `Alba' (`01-`02) (++), Veronica austriaca `Crater Lake Blue'(`00-`02), Veronica longifolia `Sunny Border Blue' (`00-`02) (++), Veronica peduncularis `Georgia Blue' (`01-`02) (+), Veronica spicata `Blue Carpet' (`02), `Icicle' (`00-`02) (+), `Noah Williams' (`00-`02), `Red Fox' (`00-`02), `Rose' (`02), `Sightseeing' (`02)
We wish to thank the Extension agents and Master Gardeners at all our garden locations for all their help with these trials. Please take some time next year to visit these trial and demonstration gardens:
Robert G. Anderson, Department of Horticulture
Lettuces, greens, and herbs are specialty crops for specialty markets. These crops may be quickly adaptable to the float beds common in tobacco greenhouses. In response to grower interest and the rapidly expanding market for organic produce, relatively soluble organic fertilizers were evaluated for the growth of Bibb and Grand Rapids lettuces in float beds in the spring and fall of 2000.
Plants were grown in plastic soufflé cups (50 ml) with holes cut in the bottom. These cups were placed into holes (plant density of 35 m-2) in polystyrene sheets (2.5 x 85 x 120 cm), and the sheets were allowed to float on the water surface of the float bed. Commercial organic fertilizers derived from fish waste (Mermaid's Fish Powder, GreenAll Fish Emulsion), digested seaweed (Algamin, EcoNutrients), bat guano, and a formulated organic fertilizer (Omega, from bonemeal, bloodmeal, and rock phosphate) were compared to a standard inorganic fertilizer (16-2-10 N-P-K) maintained in the water at 1.2 mS cm-1. Dissolved oxygen was maintained at a minimum of 4 ppm in all treatments. Lettuce (`Ostinata', `Diamond Gem', `Red Sails', `Oakleaf') fresh and dry weights were determined after four weeks of fertilizer treatment. Weekly water analyses determined available NO3, NH4, P, K, Ca, Mg, Fe, S, B, Mn, Zn, Mo, pH, EC, and alkalinity.
Organic fertilizers did not produce plants comparable to the inorganic fertilizer control during the four-week production period. Fish waste and digested seaweed were of little value for lettuce production. Commercial quality lettuce could be produced in bat guano and the formulated fertilizer but would require 10 to 20 days longer than inorganic fertilizer.
The high organic content of the fish waste dramatically reduced available oxygen in the water, so the lettuce roots could not grow in the water. Overall nutrient content of the fish waste products was low to moderate and very low in the digested seaweed. These fertilizers offer only limited hope for commercial production. Also, the nutrient levels in the bat guano and formulated fertilizer solutions were comparable or higher than those in the inorganic fertilizer. These fertilizers are good sources of nitrate, so the lettuce grew reasonably well.
These preliminary studies demonstrated that significant additional work is necessary to develop a system to utilize organic fertilizers for greenhouse production of lettuce in float beds. A formulated fertilizer seems to be the best approach to the development of a reliable nutrient solution. The Omega fertilizer was a good start but had too much P, which caused Ca and Mg deficiencies. The nutrient solution should be monitored constantly, but it would require a great deal of work to determine what additions can stabilize the nutrient levels and pH. Also these additives must meet organic certifications standards. There appeared to be lettuce variety responses to the fertilizers and the float bed system, so many varieties would have to be evaluated. In addition, visual differences in disease infection occurred among the fertilizer treatments used.
Robert G. Anderson, Department of Horticulture
Kentucky has more than 30 acres of greenhouses with modified pond or tank hydroponic beds for "float" tobacco transplant production. These facilities could be used to grow other crops during the fall, winter, and spring. Previous work has demonstrated that lettuces can be easily grown in such production systems (1,3). This study evaluated production of two types of pac choi, `Mei Qing Choi' and `Tatsoi' that could be grown in the same system and sold in Asian vegetable markets.
Plants were grown in two ways in this study. In the first system, plants floated in holes (35) cut in six 90-cm x 55-cm x 2.5-cm polystyrene sheets. The holes were 4 cm in diameter and spaced 8 x 9 cm. In the second system, plants were placed in contact with a capillary mat draped over small rectangles of 2.5-cm polystyrene (5 cm x 5 cm). The capillary mat absorbed water from the hydroponic solution to satisfy the plants' needs. The capillary mat system was used to determine if sufficient oxygen would be available to the plants' root system in non-aerated hydroponic ponds.
Six 1.08 m2 wooden hydroponic ponds or tanks were built in two rows of three on one side of a 9- x 18-m naturally ventilated sidewall plastic greenhouse. Tanks were lined with black polyethylene and filled with water to a depth of 15 cm to make a tank volume of approximately 164 L. Electric water pumps were placed in three tanks to oxygenate the water; previous work demonstrated that oxygen levels would be maintained at 4 to 6 ppm with this procedure. Brassica plants were grown in 29-ml plastic soufflé cups (Solo Cup Company, Urbana, IL) that had holes drilled in the bottom. A commercial inorganic fertilizer (Peter's 20N-4P-16.6K, Scotts, Maryville, OH) was added to the water in each tank and maintained at an EC of 1.2 dSm-1 (approximately 160 ppm NO3-N).
Seed of `Mei Qing Choi' pac choi (Brassica rapa Chinensis group) and `Tatsoi' (Brassica rapa Narinosa group) were purchased from Johnny's Selected Seeds, Albion, Maine. A single crop was grown in February 2001. Seeds were sown (Jan. 15) in the cups and germinated at an average daily temperature of 25°C. Seedlings were fertigated twice per week with 150 ppm 20-4-16.6 inorganic fertilizer before placement in the hydroponic tanks. The plants were placed in the hydroponic ponds on Feb. 5 and grew under natural light conditions. The greenhouse had a heat set-point of 16°C and a ventilation set-point of 24°C. Plants were harvested from the tanks on March 7, and dry weights were measured for nine plants in each replicate. Plants were grown with and without aeration with three replicates in a randomized complete block.
Thirty days was sufficient to grow high-quality heads of `Tatsoi' and `Mei Qing Choi' pac choi. `Mei Qing' has a relatively typical pac choi head with large, nearly white, thick petioles. On the other hand, `Tatsoi' forms a loose head of long thickened petioles with dark green leaf blades. It seems both would be fine for stir fry cooking and salads, but petioles of `Tatsoi' are similar in form to celery, rather than a pac choi.
Aeration of the hydroponic solution is clearly necessary for the production of these plants. Dry weights were nearly double for those plants in aerated treatments compared to those in non-aerated treatments, typical of a tobacco "float" bed (Table 1). Aeration is just as important for lettuce in tank or "float" bed production (1,2). In planning this experiment, it was thought that plants grown on the capillary mat would be similar in aerated and non-aerated treatments and that these treatments would be similar to the floating plants in the aerated solution. This did not occur (Table 1). The plants were too top heavy to maintain good contact with the capillary mat to receive sufficient water for normal growth. This system needs to be redesigned to re-evaluate the use of capillary mats with non-aerated hydroponic solutions. Although aeration is somewhat difficult to arrange for "float" beds, it is critical to the success of vegetable plant production in this type of hydroponic system.
| Table 1. Mean shoot dry weight (g) and standard error of ‘Mei Qing’ and ‘Tatsoi’ brassica grown with inorganic fertilizer. | |||||
| Brassica Cultivar | Aerated | Non-Aerated | |||
| Floating | Capillary Mat | Floating | Capillary Mat | ||
| Mei Qing | 3.97 + .22 | 2.54 + .16 | 1.98 + .10 | 1.79 + .11 | |
| Tatsoi | 3.55 + .20 | 2.19 + .17 | 1.84 + .10 | 1.34 + .08 | |
HORTICULTURAL CROPS—NURSERY CROPS
Robert E. McNiel and Steve Elkins, Department of Horticulture
Aesculus parviflora (bottlebrush buckeye) has made many recommended plant lists during recent times. However, few plants are available on a regular basis in the nursery trade. Seed was the main method of propagation until the 1990s when Bir and Barnes (2) established a protocol for cutting propagation. Fordham (4), in his discussion of propagation of bottlebrush buckeye, devoted his explanation to seed, except for a final comment that root cuttings and root suckers can be a source. Seed availability, timing, or facilities may still limit this plant from being propagated in significant numbers by either seed or cuttings.
Layering has been recommended as a form of propagation for plants forming suckers by several authors during the 1900s (1,8). While addressing layering in one form or another, neither Mahlstede and Haber (7), Macdonald (6), Dirr and Heuser (3), nor Hartman et al. (5) define layering as a technique for bottlebrush buckeye. Bailey (1) addresses the benefits of wounding during the layering process. As a means of producing large numbers of bottlebrush buckeye with limited facilities and less dependence on timing, we looked at mound layering as an alternative method of propagation.
Aesculus parviflora plants were planted on the University of Kentucky Horticulture Research Farm during the early 1990s in north/south rows. During 1998 the plants were bush-hogged to the ground. Multi-stem regrowth occurred during 1999 and 2000. In August 2000, research was initiated to determine if rapid propagation could occur by mound layering Aesculus parviflora . Sawdust was row mounded 18 inches deep and 3 feet wide around 41 plants. Starting in August 2000, three stems on 10 randomly selected plants were treated on a monthly basis. Treatments included cutting into non-rooting one- or two-year old stems near the base, treating with No. 3 Hormex, and keeping the stem gapped with a section of toothpick. A drip irrigation system was installed in the plot and scheduled to run 20 minutes twice a day at 9:00 a.m. and 2:00 p.m. One-GPH emitters were spaced every 2 feet along 2-inch diameter lines. Irrigation was turned off during the dormant months.
During March 2001, plants treated each of the previous months were evaluated for rooting. Plants treated during August 2000 had roots formed at the wound site on 29 of 30 stems. Plants treated in September 2000 had roots formed at the wound site on eight of 30 stems. No roots were found on stems treated during October through February. During November 2001, plants were again evaluated for rooting. Rooting had occurred on all plants treated through May 2001 (Table 1). The tendency was for more stems rooting (99%) for months (August, September, April, May) when treatments were on plants that were in active growth than when treated plants (84%) were in their dormant period (October through March). A plant was left untreated, and during March 2001 three plants were completely pruned back to within 3 inches of the ground for comparison to the treated plants. At the November 2001 harvest time, the unpruned plant had 14 stems that were rooted, and the three pruned plants generated a total of 68 rooted stems on current season growth. No other wounding or hormone treatment occurred on these four plants. Stems on these plants rooted with the sawdust treatment of mound layering and irrigation. The other 37 original plants were also producing new stems during 2001. Between untreated old growth stems and new growth stems, an additional 617 rooted stems were removed from these 37 plants, an average of 16.7 rooted stems per plant.
Rooted stems had either new coarse or fine roots. Coarse roots were most common, and it was suspected that stems with fine roots might not survive. This was not tracked as to root type, but survival of rooted stems as liners was recorded. Rooted stems were placed in 3-quart containers and overwintered in an unheated Quonset house. Eighty-three percent of the stems from treated plants leafed out and developed into the liner stage (Table 1). Ninety-three percent of the stems from untreated plants leafed out and developed into the liner stage.
Rapid propagation of Aesculus parviflora through mound layering is very feasible. Mound-layering without wounding and hormone treatment will generate rooted shoots. Stems that do not root under normal mound-layering techniques will benefit from wounding and hormone treatment.
| Table 1. Stems rooted and successfully established as a liner during month by month treatment. | ||
| Month | Rooted Stems | Survival in the Liner Stage |
| August, 00 | 30 | 28 |
| September, 00 | 30 | 25 |
| October, 00 | 25 | 22 |
| November, 00 | 26 | 19 |
| December, 00 | 25 | 19 |
| January, 01 | 27 | 16 |
| February, 01 | 25 | 23 |
| March, 01 | 23 | 21 |
| April, 01 | 30 | 27 |
| May, 01 | 29 | 24 |
Robert E. McNiel and Kirk Ranta, Department of Horticulture
Aesculus parviflora (bottlebrush buckeye) has been awarded elite status by being named to several outstanding-plant lists or to state plant-recognition programs. Individual plants displayed in retail settings have not always had comparable sales appeal. Instead of irregular or tall lanky growth, it was thought that lower branched and more uniform plants would be more acceptable by the buying public. Research was established to evaluate stem number, placement, and length as influenced by pruning plants during production. Seeds were collected from Aesculus parviflora and planted on the University of Kentucky Horticulture Research Farm during the fall of 2000. The resulting seedlings (6 to 30 inches tall) were harvested in November 2001 and individually placed in 3-quart containers. Plants were overwintered in a 13- x 48-foot unheated Quonset house covered with opaque poly. During February 2002, 130 plants were divided into three groups of 40+ plants. Three treatments consisted of unpruned stems, stems cut back to within 2 inches of the substrate line, and stems cut back to within 6 inches of the substrate line. Data were analyzed by analysis of variance using the General Linear Models Procedure (SAS).
During June 2002, data were collected as new stem counts originating from two positions on the remaining plant: originating above substrate line or from the base or below the substrate line.
The average number of shoots per plant was determined by averaging the count from two positions on the plant (above and below the substrate line) (Table 1). Unpruned plants showed apical dominance within the population. This resulted in the fewest shoots per plant (0.81) as many terminal buds continued to elongate without producing many additional shoots either above or below the substrate line. Pruning encouraged additional bud break whether pruned at 2 or 6 inches. Plants pruned at 6 inches had more of the stem remaining and thus had more buds. This yielded more total shoots (1.97) than plants pruned at 2 inches (1.58) (Table 1).
Plants pruned at 2 inches produced more shoots below the substrate line (1.90) than above the substrate line (1.26) (Table 3). Plants pruned at 6 inches produced more shoots from above the substrate line (2.47) than below the substrate line (1.47) (Table 4). For shoots that were produced, pruning did not influence average new shoot length (Table 1). Average new shoot length (inches) on unpruned plants did not differ from lengths on plants pruned at 2 or 6 inches (Table 1). Average total shoot length did present differences among treatments. On unpruned plants, average total shoot growth from below the substrate line (13.00) exceeded shoot growth originating above the substrate line (4.67) (Table 2). For plants pruned at 2 inches, no difference occurred for shoot growth for the below (14.75) and above (12.37) substrate positions (Table 3). For plants pruned at 6 inches, average total shoot length above substrate level (15.28) was statistically different from average total shoot length below substrate level (12.73) (Table 4).
Plants that were pruned did not produce flower buds, regardless of pruning height (data not shown). Unpruned plants did occasionally produce flower buds.
Plant branch height, compactness, and uniformity can be influenced by pruning Aesculus parviflora during container production practices. Pruning at 2 or 6 inches above the substrate line increased branching and improved the quality of the plant versus those unpruned. Pruning at 2 inches above the substrate line increased the number of stems arising from the base versus pruning at 6 inches. This should benefit the appearance of plants marketed in 3- or 4-quart container sizes. Work is continuing to see if either of these pruning heights will influence plant quality when it is moved to 3-gallon or larger production sizes. By achieving better quality in plant appearance through more stem development and lower branching, Aesculus parviflora may have better sales appeal at the retail level.
Statistical analysis was completed with the assistance of Dr. John Snyder, Department of Horticulture, University of Kentucky.
| Table 1. Average total number of shoots per plant (including above and below the substrate counts) and average length of those shoots for three pruning treatments on Aesculus parviflora. | |||
| Pruning Treatment | Number of Shootsy | Average Length of Shootsz (in.) | |
| Unpruned | 0.81 C | 5.17 A | |
| Pruned at 2 inches | 1.58 B | 5.93 A | |
| Pruned at 6 inches | 1.97 A | 6.20 A | |
| y | Means with the same letter for each variable are similar at p ≤ 0.01; n = 260. | ||
| z | Means with the same letter for each variable are similar at p ≤ 0.01; n = 182. | ||
| Table 2. Total number of shoots and average total shoot length produced at two positions on plants that were not pruned.z | |||
| Position | Number of Shoots | Average Total Shoot Length (in.) | |
| Above substrate | 1.30 A | 4.67 B | |
| Below substrate | 0.32 B | 13.00 A | |
| z | Means in the same column with the same letter for each variable are similar at p ≤ 0.01; n = 182. | ||
| Table 3. Total number of shoots and average total shoot length produced at two positions on plants that were pruned at 2 inches.z | |||
| Position | Number of Shoots | Average Total Shoot Length (in.) | |
| Above substrate | 1.26 B | 12.37 A | |
| Below substrate | 1.90 A | 14.75 A | |
| z | Means in the same column with the same letter for each variable are similar at p ≤ 0.01; n = 182. | ||
| Table 4. Total number of shoots and average total shoot length produced at two positions on plants that were pruned at 6 inches.z | |||
| Position | Number of Shoots | Average Total Shoot Length (in.) | |
| Above substrate | 2.47 A | 15.28 A | |
| Below substrate | 1.47 B | 12.73 B | |
| z | Means in the same column with the same letter for each variable are similar at p ≤ 0.01; n = 182. | ||
Stephen Berberich, Robert Geneve, and Mark A. Williams, Department of Horticulture
Passion flowers are members of the genus Passiflora and are among the most exotic flowers in cultivation. The Passiflora genus includes more than 450 species that, with rare exception, are tropical or sub-tropical flowering vines that climb with tendrils. Given the many passion flower species and hybrids, there is much variation to the color and shape of the flowers and foliage (5). Although most passion flowers are easily propagated from cuttings (2), there is little information available to growers about the cultural practices necessary for successful nursery production of these vines.
The overall objective of this project is to produce tropical vines with unusual flowers for the summer garden center container market using standard outdoor nursery production (Figure 1). This requires cultural practices that maximize growth and flower production.
In the summer of 2001, a preliminary study carried out using Passiflora `Blue Bouquet' determined that fertilizer concentration had a significant impact on shoot length. Accordingly, the objective of the current study was to evaluate effect of increasing fertilizer concentrations on shoot length, flower number, and bio-mass in several cultivars from diverse genetic backgrounds.
Four cultivars, Passiflora `Blue Bouquet', P. `Amethyst', P. `Fledermouse', and P. `Lady Margaret' were propagated from two node cuttings taken in early March and treated with indole-3-butyric acid (IBA) (1,000 ppm in talc) and stuck in Oasis rooting cubes. Cuttings were placed in an intermittent mist bed (5 sec. every 10 min.) with bottom heat (75°F). After three weeks, cuttings were moved to 4-inch plastic containers with a peat/bark medium (Scott's Metro Mix 360) and placed in the greenhouse. The greenhouse was maintained with day/night temperatures at 78/68°F. Plants were fertilized with a 100 ppm fertilizer solution (Peter's 20-10-20) at each watering.
Plants were moved to 5-quart containers (Nursery Supplies, Inc. Classic 500) in Barky Beaver (Professional Grow Mix, Moss, TN) southern pine bark substrate on May 15, 2002, and moved to the outdoor nursery and placed on trickle irrigation. Each container was treated with slow-release fertilizer (Osmocote 14-14-14) at 15, 20, or 25 g per container. The plants were harvested after two months of growth in the nursery (July 15) and evaluated for number of shoots, shoot length, number of nodes, dry weight, and number of flowers.
All cultivars except P. `Fledermouse' produced greater shoot length (Figure 2) and biomass (Figure 3) with 25 compared to 15 g of fertilizer. P. `Amethyst' and P. `Blue Bouquet' showed the most significant increase in shoot length (72% and 50%, respectively) and biomass (92% and 49%, respectively).
However, the results for flower numbers were quite different. P. `Fledermouse' and P. `Blue Bouquet' showed no increase in flowering at higher levels of fertilizer. Conversely, P. `Amethyst' showed a 93% increase in flower number when fertilizer was increased from 15 g to 25 g and P. `Lady Margaret' showed a 15% increase in flower number with the same increase in fertilizer (Figure 4).
One likely reason for these data is depletion of fertilizer toward the end of the production cycle. Controlled-release fertilizers such as Osmocote can increase nutrient release by as much as 30% for every 10°C increase in temperature (4). Therefore, nutrient loss can be quite severe during hot weather. During the nursery production phase, with the containers in direct sunlight, they can build up considerable heat, and the substrate temperature can rise well above ambient temperature (1). Furthermore, although the manufacturers' recommended rate of fertilizer for this size container is 14 grams, because of the high growth rate of passion flowers, a much higher concentration may be necessary. Due to nutrient leaching and the effect of increased temperatures on the controlled release fertilizers, multiple applications may be necessary to prevent nutrient supply depletion as the season progresses (3).
The differences in the data for flower numbers may be due to the genetic diversity of the plants studied. It is quite possible that some of these varieties will not flower early in the season regardless of cultural practices. Indeed, this is the most likely explanation for the results collected for flowering of P. `Fledermouse' and P. `Blue Bouquet'. Further evaluation is needed to determine if flowering is influenced by cultural practices or if flowering in these varieties is a factor of the plants' genetics.
Although P. `Lady Margaret' had the shortest shoot length of all varieties tested, it had the greatest number of flowers, and it had the highest biomass relative to shoot length. It produced a plant with much heavier shoots and leaves along with increased flowering. The increase in fertilizer concentration resulted in an increase in shoot length, flower number, and biomass for P. `Amethyst'. Two varieties, P. `Fledermouse' and P. `Blue Bouquet', produced long shoots; however, neither one had a significant number of flowers. Indeed, many of these plants had no flowers at all in time allowed by the given production schedule. Ultimately, P. `Lady Margaret' and P. `Amethyst' showed the greatest potential and were most productive when grown using this production scheme.
This study has shown that selected varieties of passion flower can be successfully grown in Kentucky as a single-season crop using the production schedule presented above. Acceptable plants can be raised in the two-month production scheme in an outdoor nursery using one application of 25 g of Osmocote 14-14-14 fertilizer. These plants have good potential as high-value, container-produced plants for patio or garden use in a market where customers are looking for exotic, tropical vines.
