The questions about applying pre-emergent weedkillers started before Christmas lights were back in the box. Well, finally the time is at hand and the stampede can begin. But please let me explain the sequence.
Scalp your lawn
This isn’t as brutal as one might guess from its name. You’re merely dropping the mower down by a notch, maybe two. Your purpose is to remove all those grass blades that were turned brown by the really cold weather in January.
By getting it out of the way you’ll be able to see your lawn’s spring green-up earlier, and the sun will reach and warm the soil more efficiently. Those are two good things. Scalping also removes a lot of the rank-growing, cool-season weeds.
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Scalping dry grass is a dusty, nasty job that requires protective gear. Wear a high-quality respirator. It doesn’t have to be a military-issue gas mask, but it ought to be better than the throw-away white things you wear when you’re painting. And wear good goggles to protect your eyes. This is a dusty job, so don’t cut that corner.
Use the clippings as mulch around your shrubs and perennials or put them into the compost pile. They’re valuable sources of organic matter for soil improvement in upcoming seasons. Whatever you do, please don’t send them to the landfill. Unless it has a recycling center for yard waste, it doesn't want them.
Time for the pre-emergents
Once you have the lawn scalped you’ll have clear access to the ground. It will be easy to apply your pre-emergent granules and get uniform coverage over your entire lawn.
Let’s take a step back, however, and identify what these granules are and why we apply them. The name “pre-emergent” gives you a clue. You apply this type of weedkiller before weeds actually germinate. They attack sprouting seedlings to prevent their developing into mature weeds. So that means they are only effective on annual weeds that start anew each year from germinating seeds (not perennials that come back from their root systems), and it means they are only effective just before the weed seeds start to sprout.
Timing is critical with pre-emergent herbicides. If you’re trying to prevent germination of crabgrass and grassburs, you must treat between March 5 and March 15. That will put down the layer of pre-emergent in waiting as the weed seeds try to sprout soon after that period.
Because Texas has a really long growing season, and because the pre-emergents that consumers normally find in stores are effective for about 100 days, you will need a second application, you might say a “booster shot,” between June 5 and 15. Without both of those treatments you will not have maximum protection.
What kind of pre-emergents are available? Several are marketed to consumers, and others are available to commercial applicators. Dimension, Team, Halts and Balan are sold for home lawn applications. Let a Texas Certified nursery professional discuss your options with you.
Remember, however, that these are pre-emergent products that are intended to stop the growth of weeds you cannot see currently – the weeds of warm weather, most notably crabgrass and grassburs (sandburs). Applied at this time these products will have no impact on weeds you are seeing in your late-winter lawn. To prevent cool-season weeds you will need to apply pre-emergent granules in late August or very early September, before their seeds start growing. We’ll talk about pre-emergent applications for them at that time.
However, rather than leave you hanging with weeds in your lawn right now, let me do the best I can to help you eliminate them. For those that are non-grassy, better known as “broadleafed” weeds, you can apply a spray containing 2,4-D to vigorous new growth. It will kill henbit, chickweed, dandelions, clover, plantain, thistles and other non-grassy invaders. Read and follow label directions for the best results. But for grassy winter weeds like annual bluegrass and rescuegrass, all you can do is wait them out and remember to apply the pre-emergent granules late this summer.
Weed-and-feed products now?
You’re going to see and hear a lot of advertising about “weed-and-feed” combination products, and the manufacturers will want you to use them very soon. While I’ve outlined in detail the various types of weedkillers and the fact that their timing is indeed coming up soon, you’ll notice that I haven’t addressed fertilizing your lawn at all. Soils are still far too cold for our warm-season grasses to be ready to utilize nutrients to full potential. Wait until April for the first feeding. If you apply fertilizer now, there is too much risk that it will get washed down the storm sewers and into our lakes. This is not a time to apply the combination materials.
Finally, a shout-out to the professional lawn care companies: They have access to other products that work over longer periods of time. They’re also unable to reach every one of their customers’ homes in a short period of time just because some guy in the newspaper said this is the perfect time to apply. You’re hiring them to do a good job. Put your trust in their results.