Can I Use 2, 4-D to Remove Weeds In My Ornamental Grasses?

“I have a pampas grass – it grows in our ditches in Iowa. Unfortunately, I have had creeping jenny find it’s way into one area of it. Can you spray the grasses with 2/4D to kill the jenny without killing the grass?” Question from Brenda of Peterson, Iowa

Answer: Pampas grass (Cortaderia selloana) survives in USDA Hardiness Zones 8 to 10, so it is not hardy in your area. I bet you are talking about either Chinese silver grass (Miscanthis sinensis), which is pictured on the photo above, or hardy pampas grass (Erianthus ravennae). Both kinds of grass are non-native and tend to become weedy in natural areas. (Let me know if either of these grasses looks like yours!)

2, 4-D will kill broadleaf weeds, but I do not recommend using it to handle your problem. Here’s why. First, these grass clumps are so dense that you probably won’t be able to reach all of the creeping Jenny invading the clump. If applied, it would kill any weeds you could access, but there is no promise it would finish the job. Secondly, 2, 4-D is pretty toxic. Protective gear is required to apply it, and it can easily drift, which can damage other broadleaf garden plants in your yard, including trees. It also isn’t good for humans or other mammals, birds, fish, etc. Here are two other management suggestion you may consider.

  1. Hand weed as much of the creeping Jenny as you can this season to keep it in check. I suggest investing in long, gauntlet gloves and a garden knife to make the process easier. Then next spring, give your grasses a low trim–6 to 8 inches above the crown. The easiest way to do this is with electric hedge clippers. Your broad-leaved weeds should start to appear before your grass really gets going. This is the best time to dig down and get those weeds at their base.
  2. Once you get your weeds in check within your grass, weed and create a mulch ring around your grass to keep new weeds from invading. Sure, birds can drop seeds into your grass clumps, but at least ground weeds will be kept from entering.
  3. Another option is to start fresh with bold, beautiful grasses that are either native or noninvasive. Starting fresh with weed-free grasses will save you time and headache in the long run if you continue to have weed problems with your current grasses. Here are three options that will pack the same punch as your tall, plumy grasses.
  • Hardy Sugar Cane: This big, bold grass has huge pinkish plumes and may reach 10 feet tall and wide. If you want a giant grass, choose this.
  • Switchgrass ‘Cloud Nine’: You will love the frothy seedheads that appear on this grass as summer wanes. It reaches 6 feet tall and turns burnished shades in fall.
  • Chinese silver grass ‘Morning Light’: This variety is said to produce very little seed, and it is very beautiful with its tall, frothy pink plumes.

I hope that these tips help!

Happy gardening,

Jessie Keith

Black Gold Horticulturist