Question of the Week – Number 1

“Does this power cold spell change when we should apply pre-emergent weedkillers in the spring?”

Three weeks ago everyone was talking about what a mild winter we were having. Would it cause summer weeds to get started extra early?

Funny, how few of those questions I’ve heard this week.

Crabgrass on left and grassburs on right can be prevented with properly timed applications of pre-emergent weedkiller granules.

This is precisely why you won’t hear me predicting when pre-emergent granules should be applied back in January or even early in February. Things can really change in a hurry. There was even one company in DFW that was running ads saying that “February 15 was the deadline!” I guess that might not have proven to be true after all.

It’s looking more and more like we’re going to be on the normal schedule for application of pre-emergents this year. That said, here are your facts.

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Using pre-emergent herbicides in the spring…
“Pre-emergent” means that these products are intended to be used before weed seeds germinate (emerge) and start to grow. Once you can see the weeds, you’re too late. In fact, weeds you can see now are almost assuredly cool-season weeds that should have been prevented by a Labor Day application of pre-emergent granules.

Granular products are probably easier for home gardeners to use. The most common types sold are Dimension, Halts (in Weed-EX) and Balan.

These are used to prevent germination and growth of crabgrass and grassburs. (The late August/very early September application prevents annual bluegrass, rescuegrass and annual ryegrass.)

Two applications will be needed. That’s because the products are effective for about 100 days, but the Texas growing season is much longer than that. We need to apply a “booster shot” 90 days after the first.

The first application should be made two weeks prior to the average date of the last killing freeze in your area. The second treatment should be made 90 days later.

These materials are safe on any type of lawngrass. They are safe around trees and shrubs. They should not be used where you intend to plant new grass this year or on top of new grass until after it has gone through its first winter. Note: Texas A&M turf specialists warn us that pre-emergents probably should not be applied to areas of turf that might have been killed by the cold and where you are likely to be planting new sod this spring. In my experience, that is most likely to happen with St. Augustine.

I am not an advocate for “weed-and-feed” products. For example, when it is proper time to apply a pre-emergent to your lawn this spring, that will be way too early to apply fertilizer. The grass won’t be growing actively enough to utilize it properly. Plus, there is too much chance of harming valuable shade trees when weed control products in the weed-and-feed fertilizers are used within their root zones.

Note: If you use a lawn care company, odds are that their timing may not coincide with what I’ve just written. You’re paying them for results. If you’re happy with what they’re delivering, that’s what really matters. They can’t possibly be on all of their customers’ lawns on the same day just “…because Neil says it’s the prime time to apply.” These suggestions are intended for use by home gardeners who are only treating one lawn – their own.

Posted by Neil Sperry
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