Weed-Killing Chronicles - April 2021


I’ll start this whole weed-killing article with an explanation of why Houston’s “Garden Goober” (er, uhm… I mean Guru) detests weed-and-feed fertilizers.

We can also blame Winter Storm Uri for this article, because the enormous number of weed-and-feed questions I’ve received have given me pause, making me realize this is a perfect opportunity to dive deep and give you all my information on killing almost any kind of weed. I will take you on a trip from why I don’t recommend weed-and-feeds to how a simple schedule can give you the thick, weed-free lawn you’ve always wanted.

So, let’s actually start with the reason I hate weed-and-feeds so much. It is because of the environmentally heinous things done by the chemical atrazine. If you stay true to my fertilization schedule, in which I emphasize using pre-emergent herbicides to keep the weed seeds from ever germinating, you will have damn healthy turf. And a healthy stand of turfgrass is the best defense against weeds in the first place.

But when we do get weed infestations, we use post-emergent herbicides that target the weeds and don’t poison the soils. Atrazine, found in weed-and-feeds, moves so readily through the soil that it will burn up roots of nearby trees. Have you ever read the warning label on a bag of weed-and-feed? It’ll scare you! They warn not to use the product several feet inside or outside any tree drip line. They also advise wearing a mask or respirator when applying the product. Yikes! And even if you don’t have trees in your lawn, atrazine is very dangerous in our groundwater, causing life-changing reactions in some animals. Some water treatment plants aren’t able to remove such chemicals.

In addition, using atrazine is similar to developing a human drug addiction - it takes a little more each time to achieve gratification. Yet you could have fewer and fewer weeds to treat if you simply grow the healthiest, thickest lawn possible. That’s the best, natural defense against weed seed germination.

You may ask, “But, Randy, don’t you endorse a company that makes weed-and-feeds?” Yes, I do! But they know I don’t recommend that particular product line. I also endorse two mulch companies that make dyed mulch, which I don’t recommend, but still approve of their better products.

Now, let me says that there are some trimec-based weed-and-feeds which I can slightly tolerate if you are absolutely bent on using one. But they aren’t really the best all-encompassing weed killer. In fact, they only work on broadleaf weeds.

Four Distinct Weed Categories - Once you know them, you’re an herbicide expert

When I first started answering garden questions for a living, I was overwhelmed by weed questions. There seemed to be no way I could ever identify all the different weeds listeners were calling about or supply the right recommendations for killing them. But it all started to make sense once I determined there are really only three weed categories to understand - grassy weeds, broadleaf weeds, and sedges. Once you identify the weed category, you’ll know what to use and when to use it.

If determining the name of a specific weed is important to you, there are whole books and websites dedicated to weed identification. I certainly don’t have the time or space to cover every conceivable annoyance here, but the best Texas weed identification site I have seen in two decades is aggieturf.tamu.edu/turfgrass-weeds/.

Broadleaf Weeds

Broadleaf Weeds

Broadleaf Weeds – These include clover, henbit, chickweed, dollarweed, sticky weed, oxalis, mock strawberry, thistle, spurge, vetch, woodsorrel, asters, Carolina geranium, wild garlic, and wild onion, just to name a few. If the leaf surface isn’t grassy-looking or very thin like a sedge, it falls into this category. Most broadleaf weed killers will work, but along the Gulf Coast, you must make sure the product is labeled “for southern lawns.” Or, make sure your type of turfgrass is listed. It truly is that simple. I’m not going to try listing the active ingredients because they all vary and most are technical names like “dimethylamine salt of 2, 4-D-Dichloropte noxyacetic acid.” Geez! I can tell you that Fertilome Weed Out and Bonide Weed Beater for Southern Lawns are two of the most highly recommended brands in this market. More importantly, they are the most readily available. But no matter what you use, you still need to add a surfactant to make it stick to the weeds as you spot-treat. (See the section on surfactants below.)

Dallasgrass

Dallasgrass

Grassy Weeds – Any weed with long, slender blades can be defined as a grassy weed. Crabgrass, goosegrass, Dallisgrass, barnyardgrass, Johnsongrass and Bahiagrass are examples. The problem with controlling these weeds is that the vast majority of grassy weed killers end up killing the turfgrass. There is one organic exception - the powder AgraLawn Crabgrass Control. But any liquid synthetic herbicide labeled for weeds such as crabgrass will kill anything green that it touches. Still, some people don’t mind spot treating grassy weed clusters, then digging out the dead stuff and covering the whole area with enriched topsoil or compost. That can help heal any turfgrass that was burnt up by the herbicide. You must also add surfactant when you spot treat with a liquid synthetic herbicide. With a powder-like control, you put the surfactant on the leaf surface, so the powder sticks exactly where you want it. You can also use liquid versions of atrazine. Yes, that’s the bad stuff in granular weed-and-feeds, but here we are spot treating leaf surfaces, so it’s not moving through the soil like the granular version. Also, liquid atrazine is only good for St. Augustine grass. It will make Bermuda and thin-bladed Zoysia a bit sick. That’s why I’ve long recommended liquid Atrazine to control infestations of Bermuda in St. Augustine.

Nutgrass

Nutgrass

Sedge Weeds – I only have to say “nutgrass” and you know what a sedge weed is. Nutgrass, nutsedge, purple sedge, yellow sedge, kyllinga, etc. Grassy-weed killers do not work on these thin-bladed weeds down to their roots, nor will any broadleaf weed control. Grassy-weed killers can burn the tops temporarily, but you need sedge-specific herbicides to get control to that “nut” - to the root system of the sedge. The three most readily available in the Gulf Coast area are Bonide Sedge Ender, Gowan’s Sedgehammer, and Monterrey’s Nutgrass Killer II. There are two active ingredients that work across the board. Sedgehammer and Nutgrass Killer II have halosufuron. Bonide’s Sedge Ender contains sulfentrazone. And, as always, it’s critical to add surfactant. Even if a product says a surfactant is in it, it’s never enough.

Virginia Buttonweed

Virginia Buttonweed

Virginia Buttonweed, Doveweed & Basketgrass – I’ve given these their own section here for several reasons.They really are broadleaf weeds, but it seems pre-emergent herbicides and typical spring and summer post-emergent herbicides don’t work on them. Cool-season herbicides and stronger-than-normal summer post-emergent herbicides will work on new growth, though. So, the best way to control these insidious weeds is to pull up all you can, whenever you can. Then treat the new growth with an appropriate cool-season herbicide October through December. Or pull up what you can in the summer and treat with an MSM-style herbicide. The problem with most MSM herbicides (Manor, Top Shot, Farenheit, Celsius, etc.) is that they aren’t really designed for St. Augustine yards, so contact on grass will cause an awful lot of yellowing. Fear not, though, because the grass should come back if you spot-treat the weeds and don’t spray the whole lawn wall-to-wall. Other herbicides are available, but they are way overpriced for me to recommend, and some require a state-issued applicator’s license, usually just for pest control and tree service companies. Once again, adding a surfactant to these herbicides cannot be overlooked.

The Importance of Surfactants – So, here’s why I recommend surfactants. We have hard water, everywhere along the Gulf Coast, and it needs to be softened to break its surface tension and essentially make the water wetter.

Technically, a surfactant is a soluble compound that reduces interfacial tension between two liquids or a liquid and a solid. In other words, it's a linear molecule with a hydrophilic (attracted to water) head and a hydrophobic (repelled by water) end.That's obviously more than you need to know, but ultimately, surfactants are important in almost any liquid herbicide. Whether you're killing weeds, unwanted grass or brush, a surfactant is always essential because our hard water tends to bead up and just roll off leaf surfaces.

Try this test: Spray a broadleaf weed killer on some clover, dollar weed or thistle. You'll see that, in most cases, the water beads up. Add a surfactant to the mix, and you'll see that it forms a sheen on the leaf surface. That's the herbicide actually sticking to the leaf and doing its intended job.

There are two ways of adding a surfactant to most herbicides. Just adding a little dish soap to the mix is the simplest way. About a tablespoon per gallon of spray will do. To keep the suds down when using over-the-counter soaps with a trigger-spray bottle or a pump-up sprayer, load the herbicide into the sprayer first, then add the dish soap. Be warned, though, that adding too little soap won't provide the surfactancy needed, and too much will create excessive tiny bubbles, often making hard to see exactly where the product is going.

I've discovered that the new-fangled, super-duper, highly infused antibacterial soaps tend to work against the goal of a surfactant. So, I recommend synthetic or professional surfactants like Hi-Yield's Spreader Sticker or Bonide's Turbo. Those two are the most readily available at retail, and they won't generate suds. I've also used the feed store version of a gallon-sized product called Alligare's Surface. If your herbicide claims that it already contains a surfactant, I suggest adding a bit more. Most manufacturers have no clue how hard the water is in our region.

By the way ... if you use one of those ready-to-use bottles of herbicide that hook onto the end of a hose, just fill the void at the top of the bottle with surfactant and shake. If you use dish soap, you will definitely get lots and lots of suds. Better, I suggest you use the herbicide as a concentrate and break it out into a pump-up sprayer at 2 to 2.5 ounces per gallon of water.

PHOTOS: Moment Open, Getty Images