Neil Sperry: Dallisgrass is the big, green monster

08/15/2014 12:00 AM

08/14/2014 12:07 PM

It’s a ruthless invader, and if we’re not vigilant, it’s set to become the turf grass that nobody asked for.

My photograph shows what has to be the world record-holder clump of dallisgrass. I came across it the other night as I was treating our grandson Joseph to a snow cone for earning his white belt, third stripe in tae kwon do. The weed was actually blocking access to the ordering window. We had to walk around it to hand them our money.

So here’s my theory on this particular clump of dallisgrass. The ground there has been beaten down by thousands of little feet that have skipped up to that window all summer long. Only the one clump of dallisgrass survived the tramplings. At first, it probably looked like some kind of desirable turfgrass, since it was the only green grass in sight. So, the way I have it figured, the kids walked around it out of respect.

And then the second half of my theory is that that clump of dallisgrass has had all the sugar water it’s needed all summer long as kids dumped their half-eaten snow cones into it — you know the flavors they mix into the same cup: bubblegum, dill pickle, cake batter and coffee. But the grass didn’t care.

Now that my serious research on this super-clump is completed, I can offer some help regarding what may become the most serious weed since nutsedge. Dallisgrass threatens all North Texas lawns, and unless we take decisive and ongoing action, it will soon be all that we have. Please let me explain.

The truths about dallisgrass

• I spelled it correctly. It was originally native to South America. It is named for A.T. Dallis, a Georgia farmer who brought it in as a pasture grass. (How can we ever thank him enough?)
• It is unbelievably perennial, meaning that it will come back from its roots year after year. It’s the cockroach of the lawn weed world. Apparently, nothing will ever eliminate it.
• Dallisgrass invades all types of turf grass — Bermuda, St. Augustine, zoysia, buffalograss. They’re all unable to withstand its assault.
• When we lost MSMA as a lawn herbicide three or four years ago, we lost any effective herbicidal spray to kill dallisgrass without harming the desired lawn grass. (See additional comments below.)
• Controlling it ASAP is critical, because every dallisgrass seed is fertile. It does not require pollination. Keep the seed heads mowed off frequently, even if you have to mow every four days.

What to do

You have two options in controlling dallisgrass.

One choice is to dig it out manually with a sharpshooter spade. You must get the entire root mass. It will be dense and disk-shaped, usually in the top 6 inches of soil. If you leave even a sliver of the root system behind, the clump will re-form.

Or, you can apply a glyphosate-only herbicide (no other active ingredients) to each clump. Use a pump sprayer for the most precise spray pattern. Sure, the glyphosate will leave you with a dead spot in your “good” grass, but it will grow in from the sides. You can minimize the size of the dead spot by using a 1-gallon milk carton with the bottom cut out. Push the carton down over the dallisgrass. Insert your spray wand into the top, and let the bottle be the shield against spray drift.

• If you watch things very closely coming out of the winter, most years there will be a short window of several days where the dallisgrass has begun greening up and before your permanent lawn grass has started to follow suit. You may be able to spot-treat with the glyphosate at that point and gain good ground in eliminating it.
• To answer the question preemptively, it is my personal experience that vinegar and home remedies of other sorts do not offer efficient and reliable control of this weed. I am comfortable that the two that I listed are the only ones I want to recommend.

Finally, it needs to be noted that because dallisgrass is a perennial weed, pre-emergent weedkillers will not offer effective control because it comes back from its roots.

However, if I owned the property on which our featured super-clump is growing, I would probably apply Halts or Dimension granules in early March and again in early June to keep the seeds from sprouting, at least for the first year and perhaps for one or two more.

That monster has probably sown thousands of seeds over the course of this one snow-cone season alone.

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