Too much shade can hurt lawns

Published 12:12am Sunday, June 26, 2011

Often, the things people plant first in new landscapes are the lawn and shade trees. As time goes on, however, sun-loving lawn grasses and shade trees don’t go together particularly well.

Shade trees grow up to do exactly what they were planted to do – create shade. Eventually, areas where grass had always grown well before will no longer get enough sun.

Bare areas occur under and around trees because conditions are too shady for grass to thrive there.

If you’re trying to deal with this sort of situation, here are some things you can do.

The amount of sunlight reaching the turf can be increased by selectively pruning trees in your landscape. The lower branches and some of the inner branches may be pruned to allow more light to reach the lawn below. Raising and thinning the canopy on older, mature trees is best done by a professional arborist who can determine which branches should be removed without adversely affecting the tree. After this is done, the existing grass will (hopefully) do better. Or if the grass has died out in the area, you can lay new sod. Remember, the tree will continue to grow, and this should be considered, at best, a temporary solution.

St. Augustine is considered the most shade-tolerant grass for our area and should be tried if shade is an issue. Understand that the word tolerance does not mean this grass thrives in the shade. All of our lawn grasses prefer full sun; it’s just that St. Augustine will do well with some shade during the day.

Ryegrasses and fescues will grow quite well in shady areas during our cool season, but they must be replanted every fall as the heat kills them in May. During summer, areas where these cool-season grasses were growing are bare.

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 and therefore have 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. Grass growing under trees needs less fertilizer because it grows more slowly, but it may need more irrigation as the tree roots compete with the grass for water.

If after these efforts you still can’t get grass to grow under your tree, it’s time to accept the situation and stop wasting your time and money trying to make grass grow where it can’t. Unless cutting down the tree is an option, you have two choices. Cover the area with a few inches of mulch, or look at the area as an outstanding opportunity to create a new garden with shade-loving plants.

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. Bare soil areas often become compacted over time. Use a garden fork rather than a shovel or spade to turn the soil under the tree because the fork will cut fewer roots.

If you need to bring in extra soil to create the bed, choose a garden soil mix high in organic matter and spread no more than about 4 inches deep. Don’t 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 an area which will cover a large part of the tree’s root system, do not apply more than 2 inches of fill.

The simplest solution is to plant the area entirely with a low-growing ground cover. I think that the three 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-spreading.

Other ground covers suitable for larger areas include ferns, such as holly fern, autumn fern, wood fern and many others, English ivy, Japanese ardisia, liriope (Liriope muscari), Algerian ivy and the asparagus fern(Asparagus sprengeri).

Many other plants thrive in partially shaded to shady conditions.

For colorful bedding plants, try impatiens, wax begonias, caladiums and torenias.

Shade-tolerant perennials include ferns, hostas, ground orchid, strawberry begonia, indigo, ligularia, aspidistra, purple heart, ajuga, cardinal flower, Indian pinks, violets and the many gingers, to name a few.

Shrubs to consider include hollies, azaleas, nandinas, cleyera, sago, hydrangea, ligustrum, aucuba, fatsia, mahonia, pittosporum, red buckeye, sasanqua, camellia, Christmas berry (Ardisia crispa) and many others.

When the lawn grass finally decides that an area has become too shady to grow there any longer, don’t fight it. Instead, open yourself up to the wonderful possibilities of planting a beautiful and satisfying garden of shade-loving plants.

Dan Gill is a LSU AgCenter horticulturist.