One of the perennial questions our arborists hear from customers is how to get more grass to grow under their trees. Whether it is from canopy shade or root growth, there seems to be a constant struggle between grass and trees. Unfortunately, most turf grass is not bred to live in harmony with large trees, and trees often find themselves in competition for resources with surrounding grass. In many cases, homeowners have to choose between uniform turf coverage and tree health.
Why Does Grass Not Grow Under Trees?
Simply put, turf grass and trees do not come from the same natural environment.
Turf grass is bred and grown to thrive in bright sun with regular watering. The root systems of sod grasses form heavy thatch that captures moisture and nutrients and reduces competition from weeds and other plants in the same area. Turf needs relatively shallow soil, as its roots are close to the surface.
Trees, on the other hand, are most at home in a forest environment. Rather than being surrounded by grass, trees in a forest cover the ground around themselves with dropped leaves or needles (yes, evergreens have a “leaf exchange” too!). This “leaf litter” acts as natural mulch and breaks down into compost, creating layers of rich soil providing both nutrients and stability to trees. This natural mulch and compost also prevents the growth of potentially-competing plants. Additionally, while the trees’ canopies need bright sun, the root zone is kept shaded, both to aid in the breakdown of the leaf litter and help prevent other plants from growing.
Turf Grass And Trees Do Not Get Along
In an urban environment, turf grass and trees are artificially united in a single ecosystem. The trees’ natural growth process and self-mulching is often altered, as leaf litter is removed by homeowners. As turf grass tries to expand into a tree’s root zone, it encounters shade and surface roots, both of which are not conducive to growth. Where trees and turf grass coexist, they often compete for resources, especially water. Lawn sprinklers and irrigation systems provide enough water for grass, but are not able to properly water trees. Synthetic fertilizers for turf grass (especially “weed and feed” products) can actually be harmful to trees.
Luckily, there are alternatives to this unhealthy cycle of competition!
What Can I Do About Grass Not Growing Under My Trees?
In an ideal world, all trees would be able to live in their preferred environment: surrounded by a large area of mulch and compost, properly irrigated, and not in competition with other plants for resources. Proper mulching around your trees will not only help the trees grow, but the mulch will regulate soil moisture and temperature, making trees more resistant to temperature shifts or periods of drought. While it may be hard to imagine a yard without grass, proper mulching around your trees and reducing the amount of turf grass brings a natural beauty and can save on water usage dramatically.
If you still want some color under your trees, rather than the natural soil, there are some ground cover options that can brighten up your yard without causing undue competition with your trees. Native grasses and groundcover that have evolved or been bred to complement the needs of trees are a great choice to reduce water usage, add beneficial nutrients to the soil, and attract native pollinators. For more information, and some specific recommendations, check out this post from our friends at Native Gardeners.
Can’t I Just Trim My Tree So That Grass Will Grow?
While it is possible to trim a tree’s canopy to increase the amount of light that reaches the ground below, and trees need a certain amount of thinning for air circulation, this is not a long-term solution, and too much thinning can lead to tree decline and death. Trees produce food and energy in their leaves, and removing leaves leads to one of two things: if a tree is healthy, it will simply grow more leaves to replace the ones lost; or, if a tree is already stressed, it will not have the energy to put out new leaves and will begging to suffer from lack of proper nutrition. For healthy trees, industry standards dictate removing no more than 25% of living canopy per year. For stressed or older trees, the acceptable percentage is even smaller. “Lion tailing” a tree (removing a majority of interior growth, leaving only small areas of canopy at the end of branches) is never an acceptable practice. If you are considering thinning your trees for light transmission, be sure to consult an ISA Certified Arborist to evaluate your trees’ health and provide guidelines for healthy trimming.
Why Does My Neighbor Have Grass Under Their Tree When I Don’t?
As with many tree questions, determining why one tree or yard seems to grow differently from another can be difficult. There are several factors that can determine how trees and turf grass will interact, including:
Tree species and age
Turf grass variety
Direction and amount of daily sun
Presence of other landscaping (shrubs, flower beds, etc.)
Micro-environmental factors (soil condition, use of fertilizer/chemicals)
Ultimately, it is up to the homeowner to choose to focus on turf grass health or tree health. Unfortunately, it is difficult to get both types of landscaping to cooperate and thrive. Before investing in costly sod installation or other landscaping, be sure to understand how grass, trees, and other plants will interact with and affect each other.
At Texas Tree Surgeons, we love trees and we love our community! While we are inveterate tree huggers and may be a little biased, it is still true that properly-cared-for trees do more to capture atmospheric carbon, reduce urban heat islands, curtail excessive water usage, and provide mental and physical health benefits. We understand it can be heard to break away from social pressure to have an immaculate, green lawn, but homeowners who have moved toward native and natural landscaping are often amazed to see how easy, beautiful, and inexpensive their trees and gardens can be. We are always happy to talk about how to organize your yard around native trees for a look that is beautiful, unique, and low-maintenance. Let us know how we can help!