Fall tree care         

By John Fulton

[OCT. 4, 2006]  The first half of this week hasn't even felt like fall, but the calendar says it has been upon us for a couple of weeks now. One of the most often asked questions is, "What do I do with my trees in the fall?" The response is, "It depends on what kind of tree you're talking about."

Pruning trees in the fall is a no-no in the early fall. Remember, pruning is a rejuvenation process. This means that cutting limbs off sends a hormone signal to the tree or shrub to grow more shoots. There isn't much of a worse time to prune than right before trees are going dormant. Late fall, meaning after Thanksgiving, is usually OK.

There are some other factors in fall pruning as well. Pruning oak trees before the end of October can lead to oak wilt. The beetles that transmit the wilt are attracted to the sap. We need to wait until there is no sap or there are no beetles.

December is a good time. Of course, you'll want to pick one of the better December days to do your pruning chores. Really the high-sap-flow trees are best done in December. This group would include maples, sweet gums and elms.

Fertilizing is a great thing, as long as you don't get carried away. Early September is really better to make use of all the nutrients, but early October is better than not doing it. Just watch the nitrogen. A lawn application rate to provide no more than a pound of nitrogen per 1,000 square feet is the norm. Providing this rate in the fall and spring (like May and September) is about ideal for trees and lawns. Also remember that vigorous growth by trees helps get away from some of the problems, such as borers. It has actually been found that trees in decline give off pheromones that attract borers and other insects to "finish them off."

Water is really an important part of fall management, especially for evergreens. As we have stretches of dry weather, it is a good idea to water. This helps keep the moisture level up in needles, and that is important to help prevent drying out later on. Watering with an inch of water in one shot is the best system. Remember, you can either add or conserve moisture. A mulch layer of at least 2 inches can go a long way in conserving what you or Mother Nature apply. Most people have seen the evergreens that dry out in late fall and winter. They have really brown needles. The addition of water before the ground freezes is important, but you may need to consider a wind buffer or use of an anti-desiccant as well. One common name is Wilt-Pruf. These products lightly coat needles to slow down the evaporation. There is nothing worse than an evergreen being short of water, having the ground frozen and having drying winds as well.

"Fall is for planting." That's one of the slogans for the fall tree planting campaign. Fall does work well, particularly for potted stock. Make sure you follow recommendations for the size hole and so on. For freshly dug stock, you've removed about half the root system by digging. This means you should probably prune off about half the above-ground portion as well. Go ahead and do it. This is the exception to the rule of no early fall pruning.

There are several questions about selecting trees. There is a tree selecting assistant available under the "Horticulture and Environment" section at www.extension.uiuc.edu. Good luck in all your fall tree endeavors.

[John Fulton, unit leader, University of Illinois Extension, Logan County Unit]