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Managing lawns in the shade

June 10, 2002|By Keith Mayberry, Imperial County-University of California Cooperative Extension adviser

Most turfgrasses do not tolerate shade very well. Bermuda grass does not tolerate shade period! Most types of turfgrass need four to five hours of full sun or a full day of filtered shade Adjacent to the north side of tall fences or north-facing walls, it is not possible to have more than a couple of hours of partial sun.

Of all the commonly grown warm-season turfgrasses, St. Augustine has the best shade tolerance (partial shade). Even St. Augustine will not grow much in deep shade. Zoysiagrass will also tolerate some shade, but zoysiagrass is very hard to establish and is slow growing.

To encourage growth of grass in the shade you need to reduce the amount of fertilizer applied. Shaded grass need half the amount of fertilizer as does grass growing in the sun.

Set the mower to a taller height (at least ½ inch higher) than you would for grass growing in the sun. The shaded grass needs all the leaf area it can muster to provide food to the plant. Higher and less frequent mowing of turf in the shade decreases incidence of diseases.


Traffic should be minimized for grass growing in the shade. Foot traffic and kids' play injure the grass, which is slow-growing already. Grass in the shade need every advantage to be able to survive under less than ideal conditions.

In the summer, a shade tree can remove 100 gallons of water a day from the soil. A lawn that is wet one day may be bone dry within two days. If the grass roots become too dry, they will start to die. A dry root system is also more susceptible to disease and decay once the lawn is irrigated again. Be sure to check often to see if the lawn needs irrigating.

Large trees, such as mulberry or Indian laurel, block out sunlight. Grass does not grow well under a tree canopy. Some homeowners have tried to modify the canopy by cutting out some branches or removing the low-lying branches. While this may seem like a good solution, there are some severe consequences. Mulberry and laurel trees respond to pruning by developing a profuse growth of small branches on the remaining limbs. When the new "twig-like" branches leaf out, the shade becomes even denser than before. In addition, the pruning wounds and potential sunburn as a result of the pruning will increase the likelihood that mulberry trees will become infected by the sooty canker fungal disease that is responsible for killing thousands of trees in the Imperial Valley.

Cool-season perennial grasses may survive the summer when grown in deep shade. We have seen Marion Kentucky bluegrass growing under mulberry trees. The grass was somewhat patchy but from a distance it gave the visual appearance of a solid lawn. Newport Kentucky bluegrass is also reported to be shade-tolerant.

There are some homeowners experimenting with tall fescues. These grasses should look their best in the late fall, winter and spring. They will barely survive the summer. You could try planting one or more types of "Eastern" cool-season grasses after the weather has cooled off in the fall. Some experts find that a mixture of cool-season grasses is better than planting just one type.

When growing cool-season grasses in the shade, do not fertilize them during the summer. Instead apply nitrogen fertilizer in the spring and fall, times when the cool-season grasses are actively growing.

Alternatives to turf for the deep shade areas include using wood chips, leaf mulch, bark, rock, brick, stone, gravel, etc. to cover the soil.

Another option is to plant shrubs or ground covers that tolerate shade such as heavenly bamboo, euonymus, ficus sp., asparagus fern (it becomes stringy in deep shade), natal plum, aralia ivy, Japanese aralia, Algerian ivy, yaupon, junipers (somewhat scraggly in deep shade), Japanese privet, dwarf lillyturf, sweet osmanthus, philodendron, photinia, Japanese mock orange, African bird of paradise (not Mexican or red bird of paradise), cape honeysuckle (it blooms less), bougainvillea (it doesn't bloom as much), dwarf star jasmine, Sandankwa viburnum and xylosma.

Tip-of-the-week: If you have flowerbeds or a vegetable garden area, now is the time to kill unwanted weed seed, and soilborne pests by solarizing. This is a fancy term by laying down a blanket of clear plastic sheeting over pre-wetted soil and letting the hot sun's rays cook the soil. First remove all the old plant debris, rocks or other obstructions. Next sprinkle the area to wet the soil to a depth of about 18 inches. Next cover the soil with clear plastic sheeting. Many stores sell inexpensive sheeting used as a drop cloth for house painting. Be sure there is good contact between the plastic and the soil. Finally cover the edges of the plastic with stone, brick, soil, or similar heavy material to prevent the plastic from blowing up in the wind. Then sit back and wait six weeks before removing the sheeting. You can spade up the soil, rewet and put the plastic sheet back down for another cycle of heating to do a better job of deep solarizing.

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