Torpedo Grass

by Marilyn
(Baton Rouge, LA)

Can you give me a suggestion about how to get rid of torpedo weeds?

Doug says he's not a Southern gardener but I do understand this is a introduced grass (Panicum repens) that is now considered a noxious weed.

The bad news is that you can't do anything about one kind of grass without killing all the other grass varieties on your lawn. No chemical tells them apart and there is no organic control that will control one and not the other either.

So you're left with removing the lawn and replacing it if you want to deal with this weed.

You can either remove the top few inches of top soil and install new top soil and sod (or seed it) to give yourself a new lawn.

Or you can do it yourself by "solarizing" the lawn. The Israeli ag people figured out that if you cover a section of land with clear plastic (during the summer) and left it on, the heat trapped under the plastic would kill darn near anything under it for a depth of a few inches.

So in LA, you can cut your turf/lawn to the lowest setting you can possibly hit with your mower. Water the lawn well to trap a lot of moisture under there and then cover with clear plastic. Weight down the edges - you don't want it blowing up or allowing any air under there. This is really important because it's all about getting and trapping heat so any new air will cool it down.


Leave the plastic there for 6-8 weeks. You'll likely see the plastic starting to rip and tear in the Southern sun about then unless you get really heavy plastic. I recommend you get the heaviest you can by the way (even greenhouse plastic if you can afford it)

The longer you leave the plastic, the better the kill will be. The research says 6-weeks and that should just do it in LA but I leave mine on much longer in the North. (all summer)

This will kill all foliage and most weed seed for a few inches down.

When you reseed or sod - do not till or work up that soil more than one-inch deep. A deep tilling may bring new seed from just below the soil-sterilization line. Sodding should only require a stiff raking or very light scarification to get the sod roots started.

The reason you just don't go in and blast it with Roundup or some other herbicide is that these chemicals will kill the adult plants but not the seeds in the soil. You kill the adults, reseed or resod and wham - those seeds germinate and the problem comes back. You need to get the seeds at the soil line and not disturb anything further down.

Good luck, let me know how it works or what you do.