Can trees and grass get along?

Published 12:00 am Friday, October 19, 2018

By Mark Martin

City of Salisbury Arborist

Everybody has heard of surf and turf. Today I want to discuss trees and turf (turf grass, that is).

Have you ever seen fescue growing in the forest? Ninety-nine percent of the time you won’t see grass growing naturally in the forest. Grass and trees have different growing requirements.

Depending on the type of tree, they tend to grow up and spread out. They shade the ground and drop a lot of leaves or needles to reduce competition.

Layers of leaves or needles hold moisture, keep roots cool and develop their own compost layer, providing a special environment for fungi to develop. Trees not only use fungi for nutrients but possibly to commutate and share resources between each other. Wow.

This environment also has an acidic pH of around 5 to 6 depending on the area. Grass tends to like more basic soils with a pH of 6 to 7.

Trees benefit from a more complete fertilizer with micro nutrients applied in early spring every few years.

Because grasses are constantly being mowed and we like grass to be green, they benefit from a fertilizer containing higher levels of nitrogen, phosphorus and potassium (NPK) that is applied multiple times each year.

Both trees and grass roots need oxygen to live, so although aeration helps decompact soils for both, trees tend to feed at their drip line. Planting grass under the canopy of trees does cause conflict.

Some trees like red maples and willow oaks naturally grow their roots very close to the surface, if not on top of the ground. Mowers, string trimmers and aerators can cause heavy damage to tree roots and trunks.

It’s also very likely that growing grass in the shade of a tree will be difficult, as grass needs at least six hours of sun in a day. Mother Nature provides trees with all the mulch needed, but humans like to rake those leaves up and put out mulch.

If you must rake leaves, my suggestion for tree rings and natural areas is to use a pine bark or needle product no more than 6 inches deep and spread at least to the drip line of the tree if possible. Please no “volcano mulch.” Too much mulch around the base of trees can cause rot and just looks weird.

I believe it’s possible for trees and turf grass to get along and there’s nothing better than having a picnic on a sunny day on the grass in the shade of a tree.

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