Start thinking about next year now! It may seem too early, but lessons can be learned now that will save time and money in the 2006 growing season.

Cultural
By planning to put more cold sensitive species away from overwintering house walls, or by using a blanket, growers can minimize cold damage to plants this winter. In previous years the sweet bay magnolias shown below were covered with a blanket inside this overwintering house and no damage was incurred. However, over the 04-05 winter a blanket was not used. Not only was cold damage present, as shown by dead or damaged plants along the outer wall of the house, but completely decayed roots were also found on plants in the interior of the house. No pathogens were detected, instead the rot appeared to be linked solely to saturated conditions. The saturated conditions were in large part due to using 50% compost in the container substrate. Compost has tendency to shrink rapidly and the resultant substrate is very water retentive due to the small particle size. In addition, compost generated from manure is often very high in salts, which can easily burn roots. A quick nitrate test of these roots in April 2005 yielded a very strong color reaction, indicating that the roots were exposed to high levels of fertilizer at some point in production. Because soluble salts were not high, the high nitrates are not likely due to a heavy spring 2005 fertilizer application, but rather a 2004 application. Research, including research done at UK, shows that due to shrinkage and salt issues, compost should be used in container substrates at a maximium rate of 20% by volume. Plan ahead and schedule deliveries so that you will have time next spring to have compost and other substrate inputs tested prior to potting up. Prior to potting up is the easiest and least expensive time to make adjustments.

Source: Best Management Practices Guide for Container Grown Plants. Southern Nursery Association. Marietta, GA, 2000.

Managing irrigation is always a challenge and the challenge is greater without some key pieces of knowledge. Take some time this fall to get those critical pieces of information together and reap the rewards next season.

Crucial to managing irrigation is knowing how much each emitter is supposed to apply per hour and how much each emitter actually does apply. (These can be two different amounts.) To monitor how much an emitter is applying, allow it to run for 10 minutes into a bucket inside an empty socket pot, measure the amount collected, and then multiply the amount collected by 6 to estimate a 1 hour irrigation application. Most emitters for pot-in-pot systems emit 5 or 6 gallons of water per hour. Exactly how much water is needed every day by each plant is difficult to estimate, but more extreme cases of over and underwatering can be avoided by simply measuring emitter output and comparing it to common industry practice. Nine gallons per day for a 15 gallon tree in pot-in-pot production is probably too much while 1-2 gallons is too little. On shade and ornamental trees in 15 gallons, a total of 3-4 gallons of water divided among 3 applications per day (cyclic irrigation) is often sufficient. A leaching fraction of not more than 25% is a good gauge of how much water to apply. More involved methods include using an evaporative pan and moisture sensors. Seasonal weather, substrate, species, as well as rate of fertilization and any other factor that affects the growth rate can influence how much water a plant uses. In addition, as the season progresses, more substrate air space is filled with roots, and more canopy has developed (which is responsible for most water loss, through transpiration), thus more water is needed. The second year in a pot, even more canopy has developed and more of the substrate has decomposed, further reducing air space. This air space in the substrate is what retains water after irrigation and is essential to providing plants with water.

If emitters vary in output greatly or otherwise appear to be clogged, clean and consider placing the stakes with emitters outside of the socket pot, in the soil. This may require a longer stake but will eliminate the need for removing the emitter when the plant is harvested. This is only practical for 180 degree spray emitters.

Source: Best Management Practices Guide for Container Grown Plants. Southern Nursery Association. Marietta, GA, 2000.