Invasive turfgrass, such as Bermuda grass or Quackgrass, presents a significant challenge in garden beds due to its aggressive growth habit. These grasses spread rapidly through specialized underground stems called rhizomes, and sometimes above-ground runners called stolons. A single fragment of a rhizome is capable of generating a new plant, making simple surface weeding an ineffective solution. Successfully removing this type of grass requires a methodical approach that targets the entire root system.
Physical Removal Techniques
Removing entrenched grass physically requires careful labor focused on extracting the full network of underground runners. Simply pulling the visible blades breaks the connection to the rhizomes below, leaving regenerative pieces in the soil to sprout quickly. Instead, the area must be loosened with a sharp spade or a garden fork to allow for the careful lifting of the entire root mass.
Follow each rhizome and stolon, which look like pale, wiry roots, back to its source and remove it completely. Aggressive grasses like Bermuda grass can have rhizomes extending six inches deep or more, requiring thorough excavation. Sifting the soil after digging helps locate and remove smaller, broken fragments that could re-sprout into new plants. Avoid using a rototiller or hoe, as chopping the rhizomes encourages the grass to multiply and spread.
Smothering and Solarization Methods
Passive techniques offer a non-chemical alternative to exhaustive digging by depriving the grass of necessary resources. Smothering, often called sheet mulching, involves covering the infested area with opaque materials to block sunlight and stop photosynthesis. Placing a thick layer of overlapping cardboard or at least ten sheets of newspaper directly over the grass initiates this process.
This dark layer must then be covered with four to six inches of organic material, such as wood chips or compost, to hold the material in place. For effective control of established perennial grasses, this setup should remain in place for at least six to eight weeks, or longer, to fully starve the underground rhizomes. Soil solarization utilizes heat instead of darkness, employing clear plastic sheeting stretched tightly over moist soil.
The clear plastic creates a greenhouse effect, trapping solar energy and raising the temperature of the top six inches of soil to 120–140°F, which is lethal to weeds and seeds. Solarization is most effective during the hottest months of the year and requires the plastic to remain in place for four to six weeks. The soil beneath the plastic must be kept moist, as water conducts heat more efficiently, ensuring the rhizomes are killed.
Chemical Spot Treatment Safety
When other methods are impractical, non-selective herbicides, which kill almost any plant they contact, can be used for targeted spot treatments. Glyphosate is one such chemical that moves systemically throughout the plant, traveling from the leaves down to the root system. This systemic action is necessary to kill aggressive rhizomes. Due to its non-selective nature, caution is necessary to protect desirable plants in the immediate area.
The safest application method involves using a foam brush or paintbrush to carefully apply the herbicide directly onto the grass blades, avoiding spray drift. Another technique uses a shield, like cardboard or plastic, to physically block surrounding plants while a targeted spray is applied. Always read the product label entirely before application to ensure the chemical is appropriate for the location, especially if the garden includes food crops, and to follow safety guidelines regarding wind, rain, and re-entry intervals.
Long-Term Exclusion Strategies
Once the grass has been removed, the focus shifts to preventing re-infestation from adjacent lawn areas. The most effective long-term strategy is installing a physical root barrier to block the horizontal spread of rhizomes and stolons. This edging material, made of plastic, metal, or concrete, must be installed deep enough to intercept the traveling runners.
A barrier depth of at least six to ten inches is recommended to block the deepest rhizomes of aggressive grasses. It is helpful to maintain a clear buffer zone, such as a path of dense mulch or a strip of bare soil, between the garden bed and the lawn. Consistent, shallow maintenance weeding that removes new shoots as soon as they appear is necessary to exhaust the root reserves before the grass re-establishes itself.