Lawn care around trees

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Lawn care can sometimes conflict with tree care and cause problems that affects tree health. Lawn maintenance consists of mowing, weed eating, watering, fertilizing, herbicide use, and adding or removing soil for flowerbeds and pathways. All of these practices can be done in a manner that does not harm the tree if done carefully around the trees. Mowing: Tree roots and trunks are often damaged by lawn mower blades and decks. Wounding tree roots and trunks harms the tree and allows disease pathogens to enter the tree, causing internal tree rot, and shortening the life span of the tree. Mowing damage can be avoided by:

• raising lawn mower blades
• mulching around trees to prevent grass growth
• controlling grass growth with herbicides

Weed eating: Young tree trunks have thin bark and are often damaged by string trimmers. If string trimmer damage is all the way around the trunk it can girdle a tree and cause mortality. Weed eating damage can be avoided by:

• placing a piece of corrugated pipe around the base of the trunk until the tree develops thick bark
• mulching around trees to prevent weed growth
• controlling weed growth with herbicides

Watering: Grass tolerates frequent shallow watering from an above ground sprinkler system, but this watering method is not beneficial to trees and can even harm them. Wetting tree trunks frequently creates a favorable environment for fungal pathogens to grow which can lead to rot. Set sprinkler heads so that they do not wet tree trunks and water grass only once per week to avoid excess moisture. Frequent shallow watering usually does not reach tree roots, especially if there is a thick layer of sod on the ground. Trees need to be watered deeply once every two weeks during dry periods. Using a soaker hose or other slow watering method is best for getting moisture to the roots. See info sheet on Properly Watering Trees for more information. Fertilizing & herbicide use: Shade trees typically do not need fertilizer. It is more beneficial to irrigate, mulch, and control weeds to improve tree growth and vigor than to fertilize. As an alternative to using chemical fertilizer, spread a thin layer of compost across the top of the ground annually to improve soil health and increase nutrient levels. If you think your soil lacks specific nutrients the tree needs, you should always have your soil tested before applying fertilizer. Find out how to take a soil sample and submit a soil test by visiting http://www.texasplantandsoillab.com/soil-testing.aspIf. Principles for fertilizer use:

• Always follow the manufacturer’s recommendations when applying fertilizer. If too much fertilizer is applied, the salts in it can stress, burn, and kill roots.
• Never fertilize at planting because tree roots need time to adjust to transplant shock. Wait at least three months after planting before applying fertilizer.
• Only fertilize in the spring. Fertilizing in late summer or fall can increase frost cracks.
• Fertilizers are activated by moisture, so always water before fertilizing, and continue watering regularly as long as the fertilizer remains active. Some fertilizers contain broadleaf herbicides, such as products labeled “Weed and Feed”. Trees are in the broadleaf category. If overused, misused, used frequently or consistently, these herbicides can cause leaf discoloration, curling, or burning, branch dieback, and even kill the tree.

If you have trees in your lawn, it is best not to use these products for weed control. Use a spot treatment that is foliar activated as opposed to a broadcast treatment which is soil activated. If overuse is recent, an activated charcoal root rinse may be used to help decontaminate the soil. Don’t add or remove soil for flowerbeds & paths: Adding soil around a tree trunk or to the top of tree roots can reduce oxygen levels and suffocate trees causing bark splitting, branch dieback, and mortality. Removing soil from around an existing tree can damage tree roots causing branch dieback or even tree death.