Will Roundup Kill Pampas Grass?

Roundup

• Roundup is a common broad-spectrum herbicide that kills pampas grass, according to Hawaiian Ecosystems at Risk. This herbicide contains glyphosate, which inhibits the plant's ability to produce proteins. When sprayed on pampas grass, it is absorbed through the plant's foliage. Roundup leaves little toxic residue in the soil. Planting in the area five to 14 days after using Roundup is safe, according to the University of Minnesota.

When to Spray

• Spray pampas grass when it is actively growing, as suggested by Hawaiian Ecosystems at Risk. Roundup is more effective when the plant is vigorously growing because it absorbs more of the toxins. Pampas grass is a warm-season grass, which means its growing season begins in spring. Spray pampas grass sometime in the late spring when the plant emerges from dormancy. Watering the pampas grass for a week before spraying promotes vigorous growth.

How to Spray

• Apply Roundup in the morning on a dry day, as recommended by Hawaiian Ecosystems at Risk. The herbicide needs at least 24 hours of dry weather to absorb into the plant. Wait three to four days for the parts of the plant start dying. Remove the dead portions of the plant and spray any remaining green leaves.

Removing Pampas Grass

• Dig up dead pampas grass. Cut the plant's bottom first and then dig up the root system. Even after the removing, pampas grass can grow back in a matter of weeks, according to Hawaiian Ecosystems at Risk. Replant the area with a native plants prevents pampas grass from regrowing. Smother its seeds with landscaping fabric if you do not want to replant with native vegetation. Secure the landscaping fabric with landscaping pins to generate enough heat to dry out pampas grass seeds.