Quack grass (Elymus repens) is a perennial grass that poses a problem for homeowners and gardeners across temperate regions. Its aggressive nature allows it to quickly dominate garden beds and lawns. Successfully eliminating this plant requires a thorough, multi-step approach that targets its complex root system. This article outlines the necessary steps, from identifying the weed to applying long-term prevention strategies, to effectively eradicate quack grass from your landscape.
Recognizing Quack Grass and Its Root Structure
Quack grass is a cool-season grass, often distinguished by its dull, blue-green foliage and thin, flat leaf blades that can grow up to a foot long. A definitive identifying feature is the presence of slender, claw-like structures called auricles that clasp the stem where the leaf blade meets the sheath. The plant’s persistence lies in its root system, composed of long, pale yellow, creeping underground stems known as rhizomes.
These rhizomes are the plant’s main method of spread and survival, typically residing within the top six inches of soil. A single plant can produce a network of rhizomes extending over ten feet, with new shoots emerging from the nodes along these horizontal stems. Simply pulling the above-ground blades will inevitably break the rhizomes, leaving behind fragments that can each sprout into a new, independent plant.
Non-Chemical Removal: Manual Digging and Smothering
For small, isolated patches, manual removal is a viable, non-chemical option, though it requires diligence. To remove it manually, loosen the soil with a garden fork and carefully trace the rhizomes back to their source. You must remove every fragment, as even a small piece containing a node can regenerate an entire plant.
Sifting the excavated soil is often necessary to ensure no rhizome pieces are left behind. All removed plant material, including the rhizomes and shoots, should be bagged and disposed of or burned, never placed in a compost pile. This labor-intensive method is most effective when the soil is moist, allowing the long rhizomes to be pulled out intact rather than snapped.
For larger infested areas, a smothering technique can be used to starve the weed of light and heat the soil. This involves covering the area with thick black plastic sheeting, cardboard, or a heavy tarp, securing the edges to block all sunlight. The plastic traps solar energy, raising the soil temperature to levels that can kill the plant tissue.
The smothering process requires a significant time commitment, often needing an entire growing season or longer to fully deplete the energy reserves stored in the rhizomes. Opaque black plastic works by entirely blocking light, forcing the perennial plant to exhaust its stored energy. After the cover is removed, any surviving shoots must be immediately pulled before they can replenish the plant’s energy stores.
Selecting and Applying Herbicides
When non-chemical methods are impractical for extensive infestations, a systemic herbicide provides the most efficient eradication strategy. The most effective option is a post-emergent product containing an active ingredient like glyphosate, which moves throughout the plant’s vascular system to kill both the foliage and the underground rhizomes. Because it is non-selective, it will kill any plant it touches, requiring careful, targeted application.
Timing the application is crucial for success, as the herbicide must be applied when the grass is actively growing and translocating sugars to its root system. The ideal windows are typically in the late spring or early fall when temperatures are moderate and the plant has produced several leaves. Applying the herbicide when the plant is stressed by drought or extreme heat will reduce the product’s effectiveness, as translocation slows down.
Proper technique involves spraying the entire foliage of the quack grass to the point of wetness, but not runoff, ensuring maximum absorption. To protect nearby desirable plants, a small paintbrush or foam applicator can be used to coat only the quack grass blades directly. A single application is rarely sufficient due to the plant’s stored energy, and a follow-up treatment is necessary two to three weeks later to eliminate new shoots.
Long-Term Strategies to Prevent Regrowth
Once the initial eradication is complete, continuous vigilance is necessary to prevent recurrence. Quack grass seeds can remain viable in the soil for several years, and any overlooked rhizome fragment can quickly re-establish the infestation. The treatment area must be monitored frequently, and new shoots should be removed immediately before they develop more than four leaves, which is when they begin to form new rhizomes.
An effective long-term strategy involves planting competitive species that will out-compete the weed for light, water, and nutrients. Establishing a dense, healthy lawn or planting vigorous groundcovers can suppress any attempts by quack grass to re-emerge. Maintaining high soil health and proper fertilization will also favor the desired plants, making it difficult for the perennial weed to gain a foothold.
For high-value areas, installing physical root barriers, such as aluminum sheeting or heavy-duty plastic edging sunk at least six inches into the ground, can prevent rhizomes from creeping in from adjacent properties. While pre-emergent herbicides are ineffective against established quack grass, they can be useful in subsequent seasons to prevent new plants from establishing via seed germination.