Get It Growing: How to beat torpedograss

When the subject of torpedograss comes up, some folks can’t resist responding with a little humor. The best way to get rid of this reviled weed, they advise, is to stick a “for sale” sign in your yard.
That may be taking things a bit far. But there is a grain of truth in this joke.
“It’s one of the most problematic and difficult grass weeds to control in Louisiana,” said Colton Blankenship, a horticulture weed scientist at the LSU AgCenter Hammond Research Station.
It’s nearly impossible to eradicate torpedograss once it has established in your lawn or garden — but there are things to you can do to keep the fast-growing weed from taking over, Blankenship said.
For starters, you need to know how to identify torpedograss so you can take action as soon as you spot it.
Torpedograss (Panicum repens) is a perennial, warm-season weed that thrives in wet conditions, even tolerating standing water. It has a distinctive, blue-gray color that stands out in the landscape. Its stems and leaves are stiff, and you’ll sometimes see hairs along leaf sheaths.
More often, however, the plant’s growth habit is what gives it away.
“It’s very likely to be taking over an area,” Blankenship said. “You’re very unlikely to find just a small amount of torpedograss.”
The weed has sharply pointed rhizomes that resemble torpedoes — hence its name.
“This is what helps it spread underground and become such a problem in the landscape setting,” Blankenship said. “It can go for very great distances, just tunneling through everything that might stand in its way. If you cut these rhizomes up, they’re going to regenerate into brand-new plants.”
It’s important to avoid doing anything that might break up and spread those rhizomes. Tilling your garden space, for example, would be a bad idea if torpedograss is present. Moving soil from torpedograss-infested areas also would be ill advised.
Because it anchors into the soil using rhizomes, torpedograss is hard to hand-pull. To keep populations in check, herbicides are the way to go, Blankenship said. Just make sure you have realistic expectations.
“A lot of the herbicides we have available, especially in landscape beds, may suppress it, but it’s going to be challenging to eliminate it, especially with just one application,” he said. “In a lawn setting, there are some different herbicides available to suppress it, but it depends on your turfgrass species, so you’ve really got to check those labels.”
For more information about torpedograss control strategies, visit www.LSUAgCenter.com/torpedograss.
Blankenship said it takes regular herbicide applications — plus time and patience — to bring a torpedograss infestation down to a manageable level.
“There’s really not a very effective way to completely eliminate torpedograss once it gets to a new location, which is why it’s so important to prevent it from getting there in the first place,” he said.