Tree shade can cause grass to not grow well, resulting in thinning lawns
It’s amazing how many times I’ve gotten questions about growing grass in shady areas. This is a common issue as shade trees in a landscape grow larger over time. Eventually, the shade they create may not allow grass to grow well in the most shaded areas. When dealing with this sort of situation, you have several options.
You can increase the amount of sunlight reaching the turf by selectively pruning trees. Lower branches and some of the inner branches may be removed to allow more light to reach the lawn below. Raising and thinning the canopy on large trees is best done by a professional arborist who can determine which branches should be removed without affecting the tree adversely. Be aware that this is a temporary solution because the trees will continue to grow over the years, and shade will once again become a problem.
You can choose a grass that will tolerate some shade. St. Augustine grass is considered the most shade-tolerant of the grasses we use for lawns. Among the St. Augustine varieties available, Palmetto is considered one of the more shade-tolerant. Don’t expect it to grow in heavy shade, however.
Grass growing in shaded areas should be mowed at a slightly higher setting on your lawn mower than normally recommended. This allows the leaf blades to grow longer, providing more surface area to absorb what light is available and produce food through photosynthesis. St. Augustine can be mowed at a height of 3 inches.
Avoid excessive fertilization because this can increase disease problems. Grass growing in the shade actually requires less fertilizer because it grows less vigorously.
If after these efforts you still can’t get grass to grow under your tree, it’s time to accept the situation (as we gardeners often must do), and stop trying to make grass grow where the shade simply won’t allow it to. Unless cutting down the tree is an option, your next step is to look at the choices for situations where grass won’t grow.
The easiest solution is to simply mulch the area. Leaves, pine straw or other mulching materials can be applied 4 to 6 inches deep over the areas under a tree where grass no longer grows well. This is relatively inexpensive and easy to do and, I think, looks very attractive and natural. After all, in nature trees grow with a layer of decomposing leaves over their roots. Simply add more mulch as time goes by to maintain a 4-inch to 6-inch depth. Weeds are rarely an issue and can easily be controlled.
Another option is to plant the area with a shade-loving ground cover or even landscape it with shrubs, annuals and perennials that thrive in shade. For inspiration, take a drive around older neighborhoods with mature trees. You’ll see how beautifully areas under large trees can be landscaped using a variety of ground covers, annuals, perennials and shrubs.
The most important thing to remember when creating landscaped areas under a tree is to respect the root system of the tree itself. Avoid severing any roots larger than 1 inch in diameter. Use a gardening fork rather than a shovel or spade to turn the soil under the tree because the fork will damage fewer roots.
If you need to bring in extra soil to create the bed, use as little as possible – preferably no more than 2 to 4 inches. Do not pile several inches of soil up around the base of the trunk of the tree because this can lead to decay. If you intend to fill over an area that will cover a large part of the tree’s root system (which extends out well beyond the reach of the branches), do not apply more than 2 inches of soil.
The simplest planting is to plant the area entirely with a low-growing ground cover. I think that the best ground covers for covering large areas are monkey grass (Ophiopogon japonicus), creeping lily turf (Liriope spicata) and Asian jasmine (Trachelospermum asiaticum). These ground covers are reliable, easy to grow and relatively fast growing.
Other ground covers suitable for larger areas include ferns, such as holly fern (Cyrtomium falcatum), leather leaf fern (Rumohra adiantiformis), autumn fern (Dryopteris erythrosora, known for its coppery red new fronds), sword fern (Nephrolepis cordifolia) and many others. Also consider English ivy (Hedera helix) and Japanese ardisia (Ardisia japonica).
Many plants thrive in partially shaded to shady conditions. Indeed, gardening in a shady area should not be looked at as a challenge or problem, but as a chance to grow a wide variety of beautiful plants. I personally enjoy gardening in the shade, particularly in the heat of the summer. Gardens in shady areas are also often easier to maintain because they generally have fewer weed problems.
When the lawn grass finally decides that an area has become too shady for it to grow anymore, don’t fight it. Instead, mulch or choose a ground cover that will thrive in the shade. Or open yourself up to the wonderful possibilities of planting a beautiful and satisfying garden of shade-loving plants.
Dan Gill is a horticulturist with the LSU AgCenter. He can be reached at DGill@agcenter.lsu.edu