Saturday, December 28, 2002
Submitted by Calvin Finch, Ph.D., Manager, Conservation Division, Water Resources & Conservation Department, SAWS, and Horticulturist
A Marvelous Year for San Antonio Lawns

 

This year was marvelous for lawns. That makes two pretty good years in a row. If your St. Augustine, zoysia, Bermuda, or buffalo lawn is in top form, it should be brownish straw colored at this time of the year. It should also be thick enough that winter weeds are shaded out. Such a lawn requires minimal care this winter. Certainly do not waste irrigation water on it. The soil is relatively moist and the grass is not using much water. If you water now you are encouraging winter weeds and making it easier for fungus to develop. There is another good reason not to waste water in the winter: SAWS and other water purveyors calculate the sewer bills for the year based on winter water use. It makes sense to do it that way because almost all water used in the winter is indoor water. All indoor water flows into the sewer and must be treated.

            Even with the good weather this year for lawns, many of us do not have grass thick enough to prevent winter weeds. My lawn is very green right now because the rescue, rye and annual blue grass have taken over the stressed St. Augustine and Bermuda grass. Even with the rain my lawn has too much shade, the soil is too poor, and the dog traffic too heavy to form a thick sod.

            Other St. Augustine lawns may also have the problem of St. Augustine Decline (SAD). St. Augustine Decline is a virus disease that attacks lawns of common St. Augustine grass. Recognize the disease by the mottling on the blade. Regular chlorosis (iron deficiency) has yellow lines running up and down the blade, SAD has the mottling. A SAD infected lawn does not respond to fertilization and watering; it thins out more each year. SAD is addressed by plugging in Floratam or other named St. Augustine varieties that are resistant to the disease.

            If you have a winter weed lawn like mine, it can be battled or enjoyed. The good news is that as long as temperatures approach 32 degrees F. every few weeks, the weeds will not grow much. Keep the lawn neat by mowing every 3 or 4 weeks. The frequency will need to be increased as we approach spring and the weeds respond to the more mild temperatures with rapid growth. Unfortunately, each of the weed grasses grows at different rates. The key is to mow enough to prevent maturation of seed heads.

            If you decide that you want to try to produce a better lawn next year, winter is a good time to aerate the lawn and top dress. Rent a plug-cutting aerator from your neighborhood rental store. If they have a 4-hour minimum, share the rental with two or three neighbors. Aeration is fast if the soil is reasonably moist. The machine cuts a plug and lays it on the surface of the lawn. The 4-inch hole is a channel for water and oxygen to reach the root system. Gases produced by natural processes can also escape. The effect is profound. Not only does the grass respond, trees grow better.

            To increase the impact of aeration, top dress the lawn with a half inch of compost after aeration. The organic material filters into the aeration channels to improve soil condition in the root zone. Compost increases water-holding capacity and drainage, encourages microbial activity, and improves nutrient efficiency.

            Compost spreading is easy and good exercise with a shovel but, if you want it to be even easier, there is at least one contractor out there, Oak Hills Top Soil & Mulch (in Boerne, 830-249-3575), who will spread the compost for you. They have a machine that works like a reverse vacuum cleaner to spread the compost evenly. Call them for their price. You may also want to check with your supplier to see if they have access to other contractors.

            The question always comes up, “Why use compost instead of top dressing?” Top dressing is sand plus compost. The sand is filler as far as I am concerned. Sand is inert material that fills space. Use top dressing to fill holes but for most impact use pure compost. Compost is where the action is.