Ornamental grasses are popular for their texture and movement, but their rapid growth and dense root systems can quickly become a maintenance problem. Running varieties that spread by rhizomes can aggressively take over garden space, requiring complete removal. Removing an established clump requires addressing both the above-ground foliage and the root mass beneath the soil.
Complete Physical Extraction
The primary removal method involves physically digging out the plant. Before removing the root ball, cut the foliage back severely, ideally to within a few inches of the ground, to make the clump manageable. For large clumps, tying the stalks together with a rope before cutting simplifies cleanup.
Ornamental grasses form a dense root crown that is nearly impenetrable with a standard shovel. Use heavy-duty tools like a sharp spade, a mattock, or a specialized digging bar to slice through the root mass around the perimeter. To lift the root ball, cut the clump into smaller sections, sometimes using a saw or an axe.
Remove the entire root crown and all attached rhizomes. Even small fragments left behind can sprout new plants, especially with aggressive varieties. Dig deeply, positioning the shovel beneath the entire root system before prying it up. Watering the area a day before removal helps soften the surrounding soil, making the digging process easier.
Passive Non-Chemical Methods
Non-chemical methods utilize environmental modification to kill the grass in place. One effective technique is solarization, which involves covering the cut-back plant and surrounding soil with clear plastic sheeting. The plastic creates a greenhouse effect, trapping solar energy and raising the soil temperature to levels lethal to the plant and its seeds.
The plastic must be sealed tightly around the edges, often by burying the perimeter in a trench, to trap heat and moisture. Solarization is best performed during the hottest months, requiring four to eight weeks to achieve lethal temperatures, which can reach 140°F in the top few inches of soil.
Another passive method is smothering, or sheet mulching, which starves the grass of light. This involves laying down a thick, opaque material like heavy cardboard or black plastic directly over the area. The material must overlap significantly to prevent light penetration and should be covered with an organic layer, such as wood chips, to hold it down. This process depletes the plant’s stored energy reserves but requires a longer timeframe, often taking six to eight weeks or more to fully kill the grass.
Strategic Herbicide Use
When manual removal is impractical, a targeted application of herbicide may be necessary. A systemic, non-selective post-emergent herbicide is appropriate, as it is absorbed by the foliage and translocated throughout the plant to kill the root system. Glyphosate is a common active ingredient and is effective against perennial grasses.
Apply the herbicide when the grass is actively growing, typically in the spring or early fall, as the plant efficiently moves the chemical down to the roots. Before application, cut the plant back partially to expose new, tender growth, which absorbs the herbicide more readily. Avoid mowing or cutting the grass for several days before and after application to maximize chemical uptake.
To protect nearby desirable plants, apply the product carefully on a calm, non-windy day to prevent overspray or drift. A waiting period of one to two weeks is required for the herbicide to fully work before the dead plant material is removed. Always follow the instructions and safety precautions detailed on the product label.
Post-Removal Cleanup and Regrowth Management
Once the initial removal is complete, the cleanup and follow-up phase ensures permanent elimination. Dispose of any removed root balls, crowns, or rhizomes in a manner that prevents re-rooting or sprouting. Do not place these materials in a home compost pile, as the roots and viable seeds can survive and spread when the compost is used.
Monitor the cleared area diligently for several weeks and into the following growing season for signs of regrowth. Small new shoots indicate that root fragments or seeds were left behind, requiring immediate attention. Remove these young sprouts by hand-pulling or spot-treating with a non-selective herbicide when they are small and actively growing.
Applying a thick layer of organic mulch, such as wood chips, to the bare soil helps suppress seed germination. Maintain this layer at a depth of three to four inches to block light and discourage new growth. Consistent vigilance and follow-up treatment are necessary for permanent elimination.