SHADY LAWN PRODUCTION
by Jerry Parsons, Ph.D.
Horticulture Specialist, Texas Agricultural Extension Service in San Antonio

Shaded lawns require special care to maintain satisfactory grass cover. That means mowing higher and more frequently, watering more often, giving particular attention to controlling leaf diseases and removing fallen tree leaves.

Shaded turf is weakened by lack of sunlight and competition for water nutrients from roots of trees and shrubs. Thus, grass that is growing in shade generally is shallow-rooted and is more succulent and less hardy than grass growing in full sunlight.

As a result, the shaded grass is more susceptible to drought stress and disease attacks. To reduce stress and to promote healthy turf, mow the grass ½ to 1 inch higher than grasses growing in full sunlight. Also, mow shaded lawns frequently enough so that only 1/3 of the foliage is removed at each mowing. Thus, grass mowed at a height of 2 inches should be mowed when it reaches 3 inches.

Because shaded turf is shallow-rooted and tree roots are competing for available moisture, water more frequently during drought stress periods. And, because grass growing in shade is not able to utilize fertilizer as readily as grass in full sunlight, fertilizer should be applied only in early spring and fall.

Leaf diseases, particularly Gray Leaf Spot and Helminthosporium, can seriously thin most lawn grass that has been weakened by the effects of shade. So apply a fungicide containing PCNB (Turfcide) or chlorothalonil (Daconil) to shaded areas at monthly intervals during the growing season. Severe disease infestations will require more frequent applications. Treated areas should not be watered for 48 hours.

It's not a good idea to use chemicals for weed control on St. Augustine grass in heavy shade because they may further weaken the grass and increase its susceptibility to disease. Trees and shrubs may also be damaged by some weed killers.

Removing tree leaves that accumulate in the fall will also help shaded grass.

In many home landscapes, shade develops to such a degree that grass cannot be maintained. Even St. Augustine grass, the most shade-tolerant of turf-grasses, requires at least 30% direct sunlight to maintain satisfactory growth. Consider replacing shaded grass areas with a bark mulch or a ground cover.

SO REMEMBER:

* Use shade tolerant grasses, such as St. Augustine or Zoysia

* Raise the height of the mower blade 1 inch. Instead of 1 ½ - 2 inches, mow up to 3 inches in height.

* Avoid excessive nitrogen which may promote diseases - particularly in shade.

* Avoid foot traffic in these areas.

* Select trees with more open crowns.

* Thin out crowns of existing trees to allow more light to penetrate.

* Improve air movement by removing solid screens of nearby
shrubbery.

*Remove fallen leaves promptly in the fall and winter.

* Prune tree limbs to a height of 8-10 feet to permit more sunlight to reach the grass.

* If the above practices do not help, try some of the shade-tolerant ground covers.

Ground covers are low growing plants that spread by underground or above-ground stems that have an inherent trailing growth habit. As these plants grow and develop, they produce a continuous mat on the soil surface.

Ground cover plants may range from woody vines to dwarf shrubs, depending on individual needs. Some of the most prominent uses of ground covers in typical situations are to cover bare areas of ground, prevent erosion of the soil, add variety to the yard or garden; regulate foot traffic in the yard or garden when used as edging for pathways, or to tie together unrelated shrubs and flower beds in the landscape.

Ground covers are frequently used under or around trees where grass grows poorly or where exposed tree roots make mowing a hazard. Ground cover plants eliminate the need for mowing as well as concealing the exposed tree roots.

Many possibilities for living ground covers are now available locally. For shade or partial shade, consider vinca, Algerian ivy, English ivy, mondo grass, and Liriope. Excellent choices for sunny locations include: Asiatic jasmine, creeping junipers, purple leaf honeysuckle, Liriope, santolina, and confederate jasmine.

Ground covers can be planted any time during the growing season. Fall and spring plantings give best results if potted or canned plants are used.

Ground covers are slower than grass in covering bare ground. Consequently, weeds are likely to grow, especially the first year. A mulch of bark, compost, or other organic material will control most weeds, as well as retain moisture in the soil. Pull the weeds by hand if they break through the mulch or use a fusilade-containing product such as Ortho Grass-B-Gon, which will kill all grass without damaging the ground cover.

Water on a regular schedule throughout the growing season, particularly during dry weather. During the winter months, water the plants thoroughly when the weather is dry and the temperature is above freezing.

Ground covers usually need pruning only to removed dead wood and keep the plantings in bound.