Plant Answers

Weekly Express-News Article
By Calvin R. Finch, PhD, SAWS Water Resources Director, and Horticulturist
Saturday, March 3, 2007

“Lawn Care”

It is too early to fertilize your lawn, but there is still plenty to do.

When the weather improves in February, many of us have the urge to fertilize the grass thinking the lawn will green up faster. It is not true. The green weeds in the lawn benefit by the nutrition, but not the dormant or semi-dormant lawn grasses. For a grass to utilize the nutrients in fertilizer, the grass must be actively growing. That growth does not begin until the air and soil temperatures have increased for a period of time, sometimes after April 15. If you apply the fertilizer before then, much of the nutrients are wasted if your goal is to benefit the lawn.

There really is no reason to ever use a “weed and feed” fertilizer/herbicide in the San Antonio area. The timing is just not correct. We apply pre-emergent herbicides now and in August, and we fertilize in late April and in October. The timing never coincides. “Weed and Feeds” are accidents waiting to happen because too many folks forget that the products include herbicides. The herbicides will kill vegetables and flowers. Use fertilizers and herbicides, but use them separately.

Aeration and top dressing is something to do right now that will benefit the lawn greatly. Rent a core removing aerator, aerate the lawn, and then spread compost one-half inch deep over the surface of the lawn. The process helps address compaction and introduces organic material to the root system with the net effect that you have a healthier and more water efficient lawn. SAWS’ customers will receive a rebate for $100 - $150 depending on the size of your lot. Visit the SAWS’ website at www.saws.org for the application and more information.

If crabgrass and sandburs or other summer weeds were a problem in 2006, apply a pre-emergent herbicide such as XL or Amaze in early March. The pre-emergents, when applied as per the instructions on the label, do a good job of preventing the germination of annual weeds. Sandburs, are especially tough to control. They require a second application of pre-emergent herbicide. In addition to this application in early March, add another layer in May as per label instructions.

Winter weeds are the issue now. Your lawn may have dandelions, rescue grass, winter rye, bedstraw, henbit, and thistles. Keep the winter grasses mowed and they can be quite attractive, the problem is that any winter weeds will stress the lawn. Pulling them by hand is very effective if you have the time. It can be satisfying because most of the winter weeds are easy to pull. It is also good exercise. Toss the weeds in the compost pile. If you would prefer to use a herbicide, consider Green Light Wipe Out. It will kill most of the weeds listed and does not hurt St. Augustine grass as long as you follow label instructions.

The live oak leaves are dropping on the lawn now. The most environmentally appropriate, and also the easiest way to deal with them is to allow the leaves to decompose on the lawn. They contribute nutrients and organic material as they decompose. Speed up the decomposition process by running the mower over the leaves. The chopped leaves disappear within a few weeks.

If you prefer to rake up the leaves, use them for mulch or in the compost pile. The leaves are too valuable to bag and send to the landfill. It is a double waste. The leaves contribute to your landscape health and they take up valuable landfill space.

A layer of four inches of live oak leaves over the root zone speeds up the growth rate of newly planted trees. Two to four inches of mulch reduce the water needed for shrubs, perennials, annuals, and vegetables. Live oak leaves are especially useful as mulch because they are easy to spread and are attractive. If after all my arguments you still do not want to use the leaves in your landscape, find a neighbor that will use them.

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