I have received a variety of e-mails requesting more information on how to care for the three types of zoysia grasses.

One from Cindy F. asks, "What is the recommended mowing height for zoysia, and if maintained at a proper height will it require regular verticutting to keep the thatch under control? And finally, if verticutting is required, how often should I expect to do it?"

All of this depends on which type of zoysia you have. Emerald, the finest-textured one, develops thatch more rapidly than El Toro, and El Toro is faster than Z3. Maintaining correct mowing height is the first step in keeping the thatch under control for all three types. Recommended height for emerald is 1/2 inch to 3/4 inch, Z3 is in the same range, possibly up to 1 inch, and El Toro can be cut between 3/4 inch to 1 1/2 inches. Keeping all of them nearer the lower range will lessen the rate of thatch buildup. A reel-type power mower will have to be used for any cut under 1 inch. Mowing frequency is just as important as mowing height. Mow often enough to comfortably keep the grass within the range. This may be once a week in the summer and less often in the winter.

How much and how often you fertilize and irrigate are also factors in thatch development. The key is moderation. Too much fertilization with high nitrogen turf fertilizers and over-watering will both cause the grass to grow faster, which means the thatch is also building up faster. Watering schedules depend on seasonal demands and on the soil type. Clay soils should be watered deeply every three days or so, sandy soils more often but for shorter watering times.

Zoysia grasses do not require much fertilization. Two annual applications of a good turf formulation is usually enough to keep the grass green and healthy. Lawns need and use more nitrogen than any other mineral supplied in fertilizers. I always recommend a formulation with at least 25 percent nitrogen (the first number on the front of the bag) with at least half of the N in a slow-release form. Look on the back of the bag for the section giving the analysis. The amount of slow-release nitrogen, if any, will be found there. Apply enough fertilizer at each application to give 1 pound of nitrogen per 1,000 square feet. For example you will need 4 pounds of a 25 percent formulation to apply 1 pound of N.

Even if staying within these mowing, fertilizing and watering recommendations, it is likely that sooner or later the thatch will build up to a point that requires verticutting. It is likely to happen more often with emerald zoysia.

An annual top dressing of compost will help to keep thatch under control, particularly if used in combination with core aeration and could substitute for one of the annual fertilizer applications. Apply a thin layer of the organic matter, no more than 1/2 inch, and rake it into the thatch layer. This is best done a day or two after mowing.

There is still time to verticut this year, but do not wait much longer. Zoysia grows slower than other warm-season grasses and requires more time to recover. Allow two months for good recovery during summer and fall; mid-September should be the cut-off for this season. Recovery will be much slower if it extends into January and February.