For The Answer
Saturday, May 1, 2004
By Calvin Finch, Conservation Director, SAWS, and Horticulturist
Lawn can be attractive, and lawn mowing is good exercise (if you use a push mower) but environmentally it is not necessarily the best choice for a landscape. Lawn grass, if we manage it in the traditional way to be lush and green all summer, requires more water, pesticides, and labor than alternative groundcovers. The alternative options include permeable hardscape and low-growing perennial plants.
Permeable hardscape is a material that covers the ground but allows water and oxygen to penetrate the soil. A concrete driveway would be impermeable hardscape whereas brick without mortar on sand would be permeable hardscape. Other good permeable hardscape options are decomposed granite, patio blocks, or flagstone surfaces, as long as mortar is not used. The surfaces are attractive, functional for use, easy to construct, good for tree roots, and water efficient. Mulch used as hardscape works for walking and is attractive but is not as good for tricycles, wheelchairs, or patio furniture. Every home improvement store and many gardening books have instructions on how to construct permeable hardscape.
Hardscape is good for deep shade under oak trees because it is often too shady for lawn grass to grow. St. Augustine and zoysia have some shade tolerance. Bermuda and buffalo grass have almost no shade tolerance. Monkey grass (also called mondo grass) prospers in the shade. A planting of monkey grass looks like lawn grass without requiring mowing, regular watering, or pesticides. It is another good choice for a groundcover in deep shade.
English ivy also provides a groundcover in the shade. It spreads much faster than monkey grass. Rooted cuttings placed every 18 inches and watered every week the first season will fill the area in just one season. Deer do not usually eat monkey grass, but they love English ivy so do not use it in neighborhoods blessed with the pests.
Asiatic jasmine is the most versatile groundcover available. It grows in shade or sun, is usually not eaten by deer, and can be trimmed to have straight edges and flat surfaces. If you prefer, it can be allowed to grow in a rolling natural manner. The foliage is evergreen and dark green. Weeds are not a problem because of the density. As good as Asiatic jasmine is for use as a groundcover in San Antonio, it has some negative characteristics to consider. Asiatic jasmine is slow to become established. If you use inexpensive 2-inch rooted cuttings, it may take three growing seasons to fill in the yard. Many nurseries offer 1-gallon containerized stock on sale at least once per year. Using 1-gallon stock speeds things up. During some cold winters the jasmine will defoliate but it quickly recovers in early spring.
Dwarf ruellia is another versatile groundcover. Plant it in sun or shade. ‘Katy’ has a blue flower and ‘Bonita’ has a pink flower. White is also available. The dwarf ruellia are tough xeriscape plants that can produce an attractive groundcover. They are not nearly as invasive as their tall cousin, the Mexican petunia. Dwarf ruellia grows to about 12-inches tall. Hummingbirds love the blooms. The deer used to pass on this plant but now eat it in most neighborhoods. The more sun that you provide to dwarf ruellia, the more it blooms.
I think buffalo grass is more suitable as a groundcover than it is as a manicured turf. Plant it in heavy soil in full sun and let it grow to 5 or 6-inches tall. The tall blades shade out weeds and the grass can go dormant during the summer. If you try to mow buffalo grass low, expect Bermuda grass and other weeds to invade the lawn
Other groundcovers to consider are cemetery iris in full sun and Texas Gold columbines under deciduous trees. Spreading junipers can be very attractive in full sun. Use the spreading nandina in morning or dappled sun. The spreading lantanas are also very effective on hot sites. The problem of winter dieback can be addressed by using attractive mulch like shredded cedar under the plants. It looks good and reduces weed growth.
Use lawn grass where you need it but use groundcovers and permeable hardscape where possible. You will use less water and after it is established you will not have to spend as much time caring for the planting.