Caring for your Trees & Shrubs This Summer

Be sure to keep trees and shrubs mulched and watered through the summer months. Organic mulches are better than gravel or rubber mulches, since the organic types encourage beneficial micro-organisms in the root zone, and they don’t heat up as much. If you’ve had problems with shotgun/artillery fungus, try using pine bark mulch (i.e., nuggets) or cypress mulch, rather than finely-ground hardwood mulches. Mulch should be 2-3” deep (more would cut off oxygen to the roots), applied out as far as possible, since the lawn grass is an enemy to the tree, competing for the same water and nutrients. Never let the mulch touch the trunk of the tree, or it can cause trunk decay and vole damage to the bark.

Trees and shrubs need one inch of water every 7-10 days. Supplement as needed, based on rainfall (you need your own rain gauge). Don’t do overhead watering of foliage in the evening, since that encourages more disease problems. If watering younger, individual trees, a 1” trunk caliper tree needs 10 gallons of water per week. Add 5 gallons for each additional inch of trunk caliper. Thus, a 5” caliper tree would need 30 gallons of water per week.

Don’t do much, if any pruning on trees and shrubs after July 1, since now that the days are growing shorter, plants sense the need to start “hardening off” for winter. Pruning any time between now and next February will “de-harden” the plant, putting it in a “growth mode” (even if new growth is not seen), resulting in tender woody tissues that could be damaged or killed by a cold winter. For the same reason, avoid fertilizing trees and shrubs until around Thanksgiving time. Roots are still active most of the winter to take up the nutrients.

Keep a close eye on plants to avoid severe damage from mites, aphids, beetles and borers. Samples of any unusual plant symptoms should be brought to your local County Extension Office before it is too late to solve the problem.

Submitted by Mike Klahr, Agent for Horticulture, Boone Co. Cooperative Extension