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Wednesday, May 22, 2013

Sensible alternative to trying to grow grass under trees

 As a Landscape Architect, one of the most common concerns I encounter is that lawns do not grow well under trees.  So I’m often asked how to make lawns grow there. 
Invariably, my response is “don’t even try!” Making north Texas lawns grow well within the root zones of trees usually means putting a whole lot of stress on trees, which often results in the tree's premature death (a tree under stress attracts more bugs, too, which can affect other plants as well). Lawns and trees are simply not compatible.

A tree’s roots are spread throughout the soil directly underneath its canopy. Contrary to what we all learned in school, most of these roots are in the top 6-inches of the soil, where the most nutrients are found. So, if a lawn is encouraged to grow in the same area where a tree’s roots are, there’ll be constant struggle between lawn and tree. This may make lawn care people happy (and wealthy) but avoid getting caught in the struggle. There are several reasons why trees and lawns don’t coexist.  


A typical lawn requires a lot of water. A typical tree doesn’t. So if you water the lawn whenever it needs it, the tree’s roots will suffer – and may rot. Also, since it’s shady under a tree, the water will stay there too long - it won’t evaporate as quickly as it does in the sun.

Typical lawns require a lot of fertilizer. Since a high level of fertilization isn’t needed by most trees, they could “overdose” on chemical fertilizer.  Some kinds will even kill them over the years. Even more damaging is the use of “weed and feed” fertilizer, or other chemical fertilizers with a high salt content, which can easily weaken or kill a tree.


Since almost all lawns require sun, and a tree creates shade, a homeowner’s impulse is to remove some of the tree’s leafy branches. But a tree needs every leaf it creates, to grow. If too many branches are removed, the tree’s ability to photosynthesize is lessened, and it suffers.


Disturbing a tree’s roots (even slightly) by tilling, adding soil or adding sod stresses the tree by interfering with its ability to obtain nutrients from the soil through its roots. This is why planting lots of cute little flowers beneath trees is a terrible idea.
Over the years, I’ve found that by far the most successful solution is to plant a ground cover under the drip zone of the tree. Forget about a lawn right there!  The goal is to grow a ground cover in as much of the tree's root zone as possible. Of course, if the tree is a newly-planted “stick”, plan the ground cover bed for the tree’s size in about 10 years.  

 Adding a layer of soil on top of the tree’s roots (putting very heavy stress on the tree), will very likely kill the tree over a period of several years. Instead, carefully plant the ground cover under trees - it's lawn. It's far better for the trees' health.

Some of the most reliable “under-tree” ground covers for north Texas are pigeonberry, vinca major, Virginia creeper, cedar sedge, inland sea oats, liriope, wood fern and horseherb. Among these I often randomly plant some shade-loving flowers (Turk’s cap, columbine, spiderwort etc.) for some seasonal color. Several do a wonderful job of attracting birds and butterflies too.
Match the tree’s preferences for water, fertilizer etc. to whatever you plant beneath it, and you’ll have a healthy, extremely low-maintenance area that’ll be a lot more attractive than half-dead grass, exposed tree roots or bare dirt.


1 comment:

  1. Invariably, my response is “don’t even try!” Making north Texas lawns grow well within the root zones of trees usually means evergreens