greennewsdaily

A common lawn challenge we hear at the nursery is thinning or dying grass under trees.The most commonly blamed culprit is the obvious lack of sunlight in that area. While shade does contribute to poor grass growth there is a lot more going on than meets the eye- literally!

Trees do not want anything growing under them and will do what is necessary to make that happen. Trees and grass are natural rivals and can interfere with each other’s growth.

Shade– The most visible limiter of grass growth. While trimming trees up to let more light in may make a slightly better environment for grass, recent studies have shown that raising tree canopy height does not prove very efficacious in getting grass to thrive and is a temporary solution at best. Heathy trees will regrow leaves and branches quickly.

Roots– Tree roots tend to be closer to the surface creating areas of low soil depths in the 1-2 inch range. Most turf grasses thrive in soil depths of 6-8+ inches of soil. Trees compete with plants (or grass) growing in their root areas for water and nutrients often using much of those available resources and leaving little for the grass. 

Chemicals– One of the largest defense mechanisms that trees utilize are called allelopathic chemicals. These are biochemicals produced by plants that can affect the growth, survival, development, and reproduction of other plants. These chemicals can be either beneficial or, more often, detrimental to the target plants. The term “allelopathy” refers to the phenomenon of one organism producing biochemicals that influence another. These chemicals are produced by tree roots as well as fallen tree leaves (like tannins in oak trees) to make the root zone area less hospitable to grass or other plant material to grow there. 

So, what can you do?

We recommend adding mulch or gravel in lieu of grass in the tree root zone areas. While mulch is preferable, gravel will usually be fine for most situations. Shade plants or groundcovers can be added to break up and add interest to these areas. Always be cautious when digging in tree root zones to minimize root damage. A minimalist approach is advisable when adding plants in tree root zones as to not disturb the trees. Mulch should be added at a depth of 2-3 inches.

If you want grass consider replacing the thinning sod with a more shade tolerant turfgrass like St. Augustine or wide blade variety Zoysia grass. 

Adding soil to tree root zones should be done in moderation. While covering any exposed roots is generally okay, adding more than 2-3 inches could cause serious issues for the tree like dormant bud sprouting (suckers at ground level) up to complete tree death

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