Quackgrass (Elytrigia repens) is a highly persistent perennial weed challenging gardeners and farmers across temperate regions. This invasive, cool-season grass does not die in the winter; instead, it survives the cold by entering a state of dormancy. This survival mechanism allows the plant to endure freezing temperatures and environmental stress, making it a formidable presence year after year. Understanding this winter survival strategy is essential for managing an infestation.
Dormancy Versus Dying
The distinction between a plant being dormant and a plant dying is fundamental to understanding quackgrass persistence. Annual plants complete their life cycle within one growing season and die completely, often leaving only seeds to germinate the following spring. Quackgrass, however, is a perennial, meaning its entire organism is built to survive over multiple years.
Dormancy is a protective, reversible state where the plant’s metabolic activity slows drastically to conserve energy. During the cold months, the above-ground foliage of quackgrass may turn brown or appear withered, which can easily be mistaken for the plant dying. This visual change is merely a symptom of reduced growth, not a sign of death, as the plant’s essential structure remains viable beneath the soil. Quackgrass retains its root system, which remains firmly attached to the ground, unlike a dead plant. It is also highly frost-tolerant, meaning its green leaves can commonly survive the winter in northern climates.
The Role of Rhizomes in Winter Survival
The plant’s resilience is entirely dependent on its underground storage organs called rhizomes, which are horizontal stems. These rhizomes function as the plant’s overwintering engine. They are packed with carbohydrates, or stored sugars, which the quackgrass collected and translocated from its leaves during the late summer and fall growing season. This energy reservoir ensures the plant has a ready supply of fuel to survive the winter and jumpstart growth very early in the spring.
Rhizomes comprise a significant portion of the total plant weight, often making up 60 to 70 percent of it. They are protected from extreme cold by the insulating properties of the soil, though they can be killed if exposed to temperatures below approximately 20°F (-6°C). Even small, severed segments of the rhizome contain enough stored energy and dormant buds to sprout a new, independent plant. This aggressive, spreading nature allows a single quackgrass plant to expand its diameter significantly in one year and produce hundreds of feet of rhizomes.
Control Strategies Targeting Dormancy
Effective control of quackgrass must disrupt its winter survival mechanism and deplete the energy stored within the rhizomes. A single treatment is rarely successful because the rhizomes contain many dormant buds and a large food supply, allowing for re-sprouting. Management requires persistence and often an integrated approach combining mechanical and chemical methods.
One of the most strategic times for applying systemic, non-selective herbicides, such as glyphosate, is in the fall. During this period, the plant is naturally moving sugars from the leaves down to the rhizomes in preparation for dormancy. An herbicide applied then will be translocated along with the sugars directly into the underground storage system, maximizing its effectiveness against the entire plant. For best results, the quackgrass should be actively growing and have at least three to five leaves to ensure sufficient leaf surface area for herbicide uptake.
Mechanical control, such as repeated deep tilling or cultivation, can also be used to target the rhizomes by exposing them to the elements. Tillage is most effective when done during hot, dry weather to desiccate the rhizomes, or in late fall to expose them to freezing temperatures. However, initial tilling must be done carefully, as simply breaking the rhizomes into pieces can inadvertently spread the infestation and activate dormant buds, causing the plant to re-sprout profusely.