March 22, 2014

The Garden Guru: For a lush lawn, it’s all about timing

Get ahead of weeds and disease and a jump on new growth.

Rants, raves, reviews and resources for Dallas-Fort Worth parents

The past several years of drought combined with this winter’s cold have left North Texas lawns languishing and in need of special attention. But your steps to corrective care need to happen in sequence, so I thought this might be a good place to list them and arrange them in rough chronological order.

Scalping. (Immediately.) This is an optional process. It’s governed by how quickly you want to be seeing green grass and whether you have a multitude of broadleafed weeds that are disfiguring your lawn. Scalping refers to dropping the mower settings by one notch. You’ll be removing the winter-killed stubble and what little bit of spring green-up that has begun showing up.

The sun will hit the soil surface, warming it more quickly. New green blades will show up more visibly, giving the appearance of faster greening. Use the clippings in the compost pile or as mulch beneath shrubs in your landscape. Do not send them to the landfill.

Pre-emergent application. (Immediately.) It’s rare that we can apply Dimension, Halts or other pre-emergent herbicide this late. The cold weather a couple of weeks ago slowed germination of crabgrass, grassburs and other warm-weather weeds. But your time is up.

Apply the granules this weekend, and water moderately to spread them across the soil surface. You get no second chance on their control. Prevent them or live with them.

Application of broadleafed weedkiller, if needed. (One to two weeks after scalping.) This is best done as a spray to coat the weeds’ leaves, and you’ll probably be applying a blend of three weedkillers known as Trimec. Nurseries and hardware stores offer several brands. Read and follow label directions for best control of the weeds and also to avoid damage to trees and shrubs.

It’s best to make the application several days after you mow and to wait several more days before mowing again. Be patient — it takes broadleafed weedkillers 10 to 15 days to do their job.

Fertilize. (Early to mid-April) Soil tests almost always show our soils to be lacking only in nitrogen. Texas A&M recommends applying a high-quality, all-nitrogen fertilizer that has half or more of its nitrogen in slow-release form. I prefer not to use fertilizers that also contain herbicides. The two processes, I feel, are better done separately.

Rake in sandy loam topsoil to fill low spots. (Late April or early May.) This may not be needed, but it’s your chance to even out the surface of your lawn if you have low spots where a tree stump has decayed or where sprinkler lines were installed. You can use topsoil, or if the fill is going to be less than 1 inch, you could use dry sand. Turn your garden rake upside down to work the sand down to the surface of the soil.

Apply sphagnum peat moss if you see take-all root rot (TARR). (Late April or May.) Once again, this may not be necessary. If you have St. Augustine (or, less often, Bermuda) that is unusually slow to green up, it may be due to the TARR fungus. Affected areas will be yellowed, and you may even be able to see the fungal strands on the runners with minimal magnification.

The peat creates a highly acidic layer at the soil surface, and that impedes development of the disease much better than any fungicide. Results are quick and significant, but again, be certain that TARR is involved before you go to this expense and trouble.

Plant new grass from sod. (April if you must, but May is better.) If you’re trying to get new grass started, wait for the warm soils of late spring. A few precautions are in order. First, do not apply pre-emergent weedkillers in areas where you are going to be planting new grass.

Do not attempt to use Bermuda seed to overseed established turf. (It is too small and cannot compete.) And, if the bare areas are primarily near shade trees, new grass may suffer the same fate as the grass that was there before. Even St. Augustine, our most shade-tolerant grass, needs five or six hours of direct sunlight daily to grow vigorously.

Apply herbicide to eliminate nutsedge, if present in turf. (Any time after mid-May.) You may call it “nutgrass,” but it’s really a sedge (triangular stems when rolled between the thumb and index finger). It’s our most persistent weed, but products such as the original Image or Sedgehammer will eliminate it. Talk to your nurseryman. Read and follow label directions carefully.

Make a second application of pre-emergent herbicide. (Mid-June, 90 days after the first treatment.) This is the booster shot of preventive material, either Dimension or Halts. It is an important treatment for a full season of control of crabgrass and grassburs, but only if you made the first treatment.

Make a second application of fertilizer to turf. (Mid-June.) This should be the same all-nitrogen lawn food you applied in April. In the case of St. Augustine turf, it will be your last feeding until the final feeding of the year in early September. With Bermuda, you should fertilize again in early August and early October.

And that gets you into mid-summer’s lawn-care program. Lots of things can happen between now and then, so we’ll not project any further at this point. Hopefully we’ll all be enjoying great turf and ample rainfall by then.

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