Lawns vs. Shade trees: Which One Wins?

Lawn vs. Tree

Wonder why you can’t grow a lush lawn under your large shade trees? What about that supposed “shade tolerant” grass that is thinning out in the shade? Lawns and shade trees don’t go hand in hand, but there is a lot of marketing about shade tolerant grasses. If your lawn isn’t thriving under your large trees, there are a few important reasons why it’s struggling.

Grasses need at least 6 hours of direct sunlight to thrive.

Lawns Love Sun

Lawngrasses, in general, are sun-loving plants that need at least six
hours of direct sunlight to thrive. And by “thrive” we mean that the
lawn grows densely and vigorously, without thinning out. There are some
varieties of lawngrassses that are considered more shade tolerant. But
shade tolerant does not mean shade loving. Even shade tolerant grasses
will thin out in too much shade and can completely fail in dense shade.

St. Augustine is most typically planted in shady situations, but even
its shade tolerance has a limit – and in the full shade found
underneath large trees such as live oak and pecan, it will slowly thin out
and succumb to low light levels.

You may look longingly at your neighbor across the street with shade
trees and a pretty lawn and wonder why your grass can’t look the same.
The angle of the sun, placement of your home, height of the tree
canopy, and surrounding structures, can make all the difference. Not all shade is the same. Light
levels will vary significantly in each space. Just because your
neighbor’s lawn looks good, doesn’t mean you have the correct sunlight
levels and duration for a happy lawn.

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No amount of extra water or fertilizer will substitute for adequate light for your lawn.

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Keep the Lawn or the Tree?

Ultimately, you may need to choose between your trees or your lawn.
Obviously, trees are crucial to our urban environment, and we never want
to remove or damage trees just for a lawn, if we don’t have to. We
typically recommend transitioning shady lawn areas over to shade-loving
groundcovers or mulch. The area will look much nicer with the
appropriate plant choices, and you’ll have a lot less maintenance to
deal with. Bonus!

Be careful – there are things you shouldn’t do:

The health of your trees is affected directly by what you decide to grow and do below their canopy.

• Overapply mulch near the trunk. If it looks like a volcano then you need a mulch do over!
• Improperly limb up your trees or thin out the canopy
  to try to let more light in just for a little bit of lawn growth.
  Unnecessary thinning weakens your trees and makes them susceptible to
  breakage, along with pests and diseases.

• Till extensively beneath your trees. Your tree’s important
  feeder roots are located near the surface of the soil. When you till or
  dig extensively under your tree’s canopy, you do serious damage to the
  root system that takes up water, nutrients, and air. Rather than tilling up all the soil, or digging big beds, plant
  individual small groundcover plants so as to cause the least amount of
  root damage possible. Spreading groundcovers will eventually fill in the
  area on their own.

• Overwater & overfertilize the lawn to try to get it to fill out.
  You can’t replace sunlight with water or fertilizer. This will not work
  & will adversely affect your trees. It can also encourage many fungal diseases.

• Allow groundcovers to grow up tree trunks. They can easily girdle and rot the base of your trees. You should always be able to see the root flare.

Don’t let groundcovers girdle your trees. The root flare should always be exposed.

Unfortunately, lawns often lose the battle when they go up against large shade trees. But the value of trees in our urban environment is undeniable: better air quality, lower energy costs, cooler temperatures, higher property values, beauty, and habitat for wildlife. We think that’s a good trade!