Quack Grass (Elymus repens) is a highly persistent, perennial weed found across temperate regions globally. This invasive grass thrives in gardens, lawns, and agricultural fields, quickly outcompeting desirable plants due to its robust growth and deep-rooted nature. Controlling this invader requires understanding its distinct physical traits and aggressive means of reproduction.
Identifying Characteristics and Nomenclature
This common weed is known by many names, including couch grass, twitch grass, and quitch. Its scientific classification places it within the genus Elymus. For identification, look closely at the leaf blades, which are typically flat, rough, and range from 3 to 10 millimeters in width. A distinctive feature is the presence of small, claw-like appendages called auricles located at the base of the leaf, which clasp the stem.
When the plant matures, it produces a narrow, upright spike for a seed head that often resembles a miniature head of wheat. These seed heads contain spikelets arranged in two rows along the stem, usually appearing from mid to late summer. The combination of the clasping auricles and the underground root structure helps distinguish Quack Grass from other lawn invaders.
The Mechanism of Aggressive Spread
The primary reason for Quack Grass’s persistence is its extensive network of underground horizontal stems, known as rhizomes. These rhizomes are typically pale yellow or straw-colored, sharply pointed at the tips, and function as underground storage organs for energy reserves. They allow the plant to spread rapidly, with a single plant capable of extending its diameter by several feet in a year.
Even small fragments of a rhizome that include a single node are capable of regenerating an entirely new plant. This regenerative capacity means that traditional methods like tilling or shallow weeding can inadvertently chop the rhizomes into numerous pieces, multiplying the infestation. The plant also produces seeds, which can remain viable in the soil for up to five years, contributing to secondary spread. Furthermore, Quack Grass may release allelopathic toxins, chemicals that suppress the growth of nearby competing plants, further aiding its dominance.
Targeted Control and Removal Techniques
Controlling Quack Grass requires persistent and targeted strategies, often combining cultural and chemical methods. For small, isolated patches, manual removal is an option, but it must be done with extreme care to ensure every piece of the yellow rhizome is dug out and removed. The removal depth must extend well below the surface, as most rhizomes are found in the top 10 centimeters of soil.
Cultural Methods
Cultural methods focus on depriving the plant of the resources it needs to survive. Smothering the infestation with a thick layer of opaque plastic or cardboard for an entire growing season can deprive the grass of sunlight, eventually starving the rhizomes. Another technique, solarization, involves covering the area with clear plastic sheeting during the hottest months to superheat the soil, which can destroy the rhizomes. Promoting a dense, healthy stand of desirable grass or crops will also help by shading the Quack Grass, as it does not tolerate low light conditions well.
Chemical Control
Chemical control is often the most effective method for larger infestations, typically involving a non-selective, systemic herbicide like glyphosate. Systemic products are absorbed by the leaves and transported down to the rhizomes, killing the entire plant. Since these herbicides kill all green vegetation they contact, they must be applied as a spot treatment, meaning the area will need to be reseeded afterward. The optimal time for application is when the Quack Grass is actively growing, often in the spring or fall, or when the plant is between four and eight inches tall to maximize the herbicide translocation to the roots. Due to the high energy reserves in the rhizomes, multiple applications, spaced several weeks apart, are necessary to achieve complete elimination.