What is Barnyard Grass and How Do I Control It?

Howard F. Schwartz, Colorado State University,

Barnyard grass is one ugly weed that likes to show up in summer to wreck your lawn by robbing it of nitrogen and other nutrients. Since it relies on seeds to spread, the key to controlling barnyard grass is catching it early and killing it before seeds develop.

What You Need to Know About Barnyard Grass

  • Warm-season annual grassy weed with thick stems that have a maroon tint near the base
  • Leaves are flat and smooth, ranging from 4-12 inches long
  • Leaves have distinct white midvein
  • Seedheads will look spiky and can be 4-8 inches long with a green, red, or dark purple tint
  • Thin, branching root system
  • Spreads by scattering seeds
  • Can grow up to 5 feet tall


Like crabgrass and foxtail, barnyard grass is an annual grassy weed. It loves moist, well-fertilized lawns and is easily recognizable thanks to its purple-tinged stem, long, flat leaves (each with a prominent vein running down the middle), and a tendency to sprawl. It's even easier to spot when it blooms, producing a bristly purple seedhead – but don't wait until this point to take action. Barnyard grass produces loads of seeds, so you need to kill it while it's young.


  1. Give Your Lawn Some TLC.
  2. A thick, well-maintained lawn is the best way to prevent weeds like barnyard grass from moving in and taking over. By regularly feeding your yard (4 times per year), you'll encourage grass growth that's lush and full, leaving little room for weeds.
  3. Don't Pluck It Out.
  4. Hand-pulling is, to be honest, a time-waster. If you don't get every single bit of root, barnyard grass will grow back. What's more, if you don't kill it before it produces seeds, it's almost guaranteed that you'll be dealing with barnyard grass again next summer. So instead...
  5. Spray It with Roundup® For Lawns.
  6. The most effective way to control barnyard grass is to spray it with a weed control product made for use on lawns, like one of the Roundup® For Lawns products. That way, you'll be able to KO barnyard grass – and other weeds listed on the label – without doing any damage to your grass (just be sure to use as directed). To treat small or large areas of barnyard grass, reach for Roundup® for Lawns3 Ready-To-Spray (for Northern grasses) or Roundup® for Lawns6 Ready-To-Spray (for Southern grasses).
  7. You can also use it in a tank sprayer with Roundup® For Lawns2 Concentrate (for Northern grasses) or Roundup® For Lawns5 Concentrate (for Southern grasses). Don't be surprised if you need to treat this weed pest more than once, either, as barnyard grass can be difficult to kill.