Growing lawns under trees

The area under trees is often "dry shade"

Just as "grass doesn't grow on a playground" it often has a tough time growing under trees.

A combination of factors makes growing grass under trees very difficult. Lawn grasses not only have to compete with tree roots for moisture and nutrients, they also have a tough time getting enough sunlight. Therefore, there are several steps you can take to encourage lawn growth in the dry shade under trees.

The area beneath a tree can be very dry as well as too shady for a good lawn. Thin tree branches to allow more sunlight to reach the lawn. Consider using mulch or ground cover in extremely shady areas.

Keeping grass growing under a tree

In order to grow grass under a tree, you will need to do the following:

Thin-out tree branches to allow the maximum amount of sunlight to reach the ground. You will need to repeat the thinning-out procedure every few years. Avoid "topping" trees if at all possible.
Mow the lawn at the tallest height possible without the grass laying-over. Longer grass blades are able to intercept more sunlight. Also, longer shoots mean deeper roots!
Water lawn areas beneath trees thoroughly once a week during dry spells. Tree canopies can shed rainwater away, making the soil beneath trees extremely dry. In addition to that, tree roots remove moisture from the soil, creating severe competition with lawn grasses.

Planting grass under a tree

In spite of proper thinning, mowing, and watering, shady areas under trees often need to be reseeded every year or two. It's often necessary to add just enough soil to create a seed bed, since the existing soil can be filled with fibrous roots. While it can be very detrimental to add soil over most tree's root zones, limited soil fill over some tree roots shouldn't cause any major problems.

IMPORTANT NOTE: The depth and extent of the soil fill should be limited as much as possible. Some tree species can be killed by just a couple inches of soil over their root zones. Consult with a professional landscaper or arborist before adding soil to a tree's root zone.

In the example below, we were contracted to seed an area beneath a pin oak that had recently been thinned-out by a tree service. Due to the mature size and species of the tree, it was determined that adding a thin layer of soil to the root zone wouldn't cause any serious problems.

Area beneath the tree has very little lawn grass

BEFORE: The area beneath this Pin Oak was very shady before a tree service thinned the canopy to permit more sunlight to reach the lawn surface.

Tree root zone has been covered with a thin layer of soil

A thin layer of shredded topsoil was used to smooth the area and create a seed bed.

Area has been seeded with a shade mix comprised mostly of fescues

The area was then seeded with a "shade mix" consisting mostly of Fescues. Starter fertilizer was also applied to encourage new and existing lawn grasses.

One month later the existing grass and seeded areas are looking much better

AFTER: One month later, the tree's root zone looks like a lawn again. Proper follow-up care (as outlined above) will be necessary to keep this lawn looking good.

SUMMARY

In most cases, tree roots will eventually find their way back to the lawn surface, and this sort of "fix" may only be temporary. If you have an extremely difficult area that seems impossible to grow grass, consider mulching the area or planting a shade-loving ground cover. Remember to check with a professional before adding soil to a tree's root zone.

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