Henbit is among the first broadleafed weeds to start blooming in spring.

Special to the Star-Telegram

You get one chance and only one chance to get rid of annual bluegrass (Poa annua), and that chance is now.

You get rid of it by never letting it get started! If you don’t know that weed, it’s the little grass with hundreds of seedheads that overruns area lawns in March, April and May. If you’ve had it in the past, and if you don’t deal with it now, there’s a 100 chance that you’ll have it again.

The same steps I’m about to outline will also protect you from rescuegrass, ryegrass, foxtail and other annual, cool-season, grassy weeds. I’m going to reduce my instructions to short points to help keep things clear.

This is a really critical message, but it can get a bit complicated.

The weeds controlled

Annual bluegrass (Poa annua), rescuegrass, ryegrass, foxtail and any other weed grass that germinates in fall and becomes unsightly by spring.

The products

There are several, but most common among them are Dimension, Halts and Balan. They’re available in independent retail garden centers, hardware stores and feed stores. They will be listed as giving “pre-emergent” control of weeds. Quite commonly they will be labeled as “crabgrass preventers,” but this fall application is not intended to be used for that purpose.

The timing

August 25 through September 5. This year let’s broaden it to include all of Labor Day weekend, so we’ll say through September 7. It’s not so precise that adding two days will mess up the schedule. You just don’t want to be showing up with your pre-emergent granules and gear in the middle of September.

How they work

Applied to the soil and then watered moderately to disperse them across the surface, these pre-emergent granules create a barrier of the product that inhibits the development of roots from the sprouting seeds. They’re effective for approximately 100 days, although very heavy rains can shorten that effective life.

Are there restrictions?

Pre-emergents should not be used on new lawns until they have gone through their first winters. That’s especially critical for newly seeded turf, or for sod that has been planted during the summer or early fall. Most brands are cleared for use on any type of turfgrass and beneath trees, but read and follow label directions closely for product-specific instructions. Only one application should be necessary during that 2-week window of August 25-September 7.

What are the sequences in application?

Assuming you’re going to be conducting other lawn maintenance tasks, here would be the schedule:

  • Mow at the recommended height.
  • Fertilize with a high-quality, all-nitrogen lawn fertilizer that has upwards of half of its nitrogen in slow-release form.
  • Water deeply to soak the nutrients into the soil.
  • Wait two days, then apply the pre-emergent(s), then water moderately.

A word on broadleafed winter weeds

To this point I’ve addressed only the grassy winter weeds. That leaves an entire category of even more unsightly invaders as yet unmentioned.

What do we do about them?

Dandelions, henbit, chickweed, clover, plantain, thistles and more. Isn’t there something we can do to prevent them?

Indeed. The pre-emergent Gallery applied in that same 2-week window that closes on Labor Day weekend will prevent their germination, too. But here are pointers you’ll want to keep in mind.

There is no combination product that contains pre-emergent granules for both grasses and broadleafed weeds. You’re going to have to make two passes over your yard to apply the two products. That’s no big problem. You can do so on the same day, but you have to make the two passes over your lawn. Don’t try to combine them in your spreader’s hopper. The granule size variations keeps them from distributing uniformly. Once you’ve made that second application, then you can water both products onto the soil surface.

Second, broadleafed pre-emergents are considerably more expensive than the granules you’ll buy for the grassy weeds. That’s just the way it is, so if you intend to use them, don’t be surprised.

Finally, broadleafed weeds do give you a second chance. You can apply a broadleafed weedkiller spray (containing 2,4-D) in late fall to kill the small seedling weeds as they start to take hold and grow. They are relative inexpensive. As a result, you may opt for the late fall spray if broadleafed weeds show up in your lawn.

But not so with the grassy weeds. As I said at the outset you get only one chance to stop them, and that chance is here now. This is the time to apply pre-emergent weedkiller granules! Don’t you dare miss it!

You can hear Neil Sperry on KLIF 570AM on Saturday afternoons 1-3 pm and on WBAP 820AM Sunday mornings 8-10 am. Join him at www.neilsperry.com and follow him on Facebook.

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