Pampas grass is a large ornamental grass from South America and is invasive in some parts of the United States. If one of these large grasses grows in your yard and you want to eliminate it, use both mechanical and chemical methods. Trim early in the growing season, and apply the herbicide to new growth before frost.
Trim the pampas grass
Cut stalks to approximately 3 feet in height before the plant blooms. A single pampas grass plant produces up to 100,000 seeds and disperses them through the air, where they travel up to 20 miles before landing.
Apply the herbicide
Use an herbicide containing glyphosate, if allowable in the area where you live. Reduce overspray that kills other plants by applying it to new growth with a paintbrush. Products should kill the remaining growth within a couple of weeks. If you see new growth during this period, reapply the herbicide.
Remove any plant material
At this point, some homeowners choose to leave the roots and remaining grass to die and rot in the ground. Others choose to pull the grass and roots from the ground to prepare the area for planting. In areas where the authorities don't allow herbicide, pull the plants and place them in plastic bags for disposal. Work the soil to ensure you remove all the plant matter if aren't using herbicide.