Watergrass, most often identified as Barnyardgrass (Echinochloa crus-galli), is an invasive annual weed that quickly degrades the appearance and health of a lawn. Its aggressive growth and preference for moist conditions make it a frustrating problem for homeowners seeking a uniform, dense turf. Effectively managing this weed requires a comprehensive strategy that addresses the environmental factors contributing to its presence. Understanding its life cycle and implementing both cultural and chemical controls is necessary for lasting eradication.
Identifying Watergrass and Understanding Its Growth
Watergrass is a warm-season annual grass that thrives when soil temperatures rise in the late spring and early summer. The plant completes its life cycle within a single growing season, germinating, producing seed, and dying with the first frost in the fall. Its rapid growth allows it to quickly outcompete desirable turfgrasses for light, water, and nutrients.
Proper identification is the first step in control. Its leaves are typically broad, pale green, and feature a noticeable midvein running down the center. A distinguishing feature is the complete absence of a ligule or auricles where the leaf blade meets the stem. The stems often have a reddish-purple tint near the base, and mature plants produce dense, spiky seed heads that can contain thousands of seeds.
Cultural and Manual Removal Techniques
For minor infestations, physical removal is a viable, non-chemical option, provided it is done before the plants mature. Hand-pulling is most effective when the plants are young and the soil is damp, ensuring the entire root system is extracted. Allowing the plant to produce seeds, which occurs from July through September, will guarantee a more severe infestation the following year.
Adjusting irrigation practices is a fundamental cultural control because watergrass prefers perpetually wet soil. Reducing the frequency of watering while increasing the duration of each session encourages the turfgrass roots to grow deeper. This helps the topsoil dry out between waterings, creating a surface environment less conducive to watergrass seed germination.
Mowing height also plays a significant role in suppressing the weed’s growth. Maintaining a higher cut height, typically above three inches, helps desirable grass shade the soil surface. This shading blocks the sunlight needed to stimulate watergrass seed germination. In non-turf areas like flowerbeds, applying a thick layer of mulch or using solarization techniques can physically block growth and kill seeds.
Selecting the Right Herbicide for Eradication
Chemical control offers an effective method for managing widespread or recurring watergrass problems, requiring a dual strategy. The most effective long-term approach is using pre-emergent herbicides, which target the weed seeds before they sprout. These products, containing active ingredients like prodiamine, pendimethalin, or dithiopyr, must be applied in the early spring.
The application timing for pre-emergent products is determined by soil temperature, not the calendar date. Application should occur before the soil consistently reaches 62 degrees Fahrenheit. Applying the herbicide too late allows the seeds to germinate, rendering the pre-emergent ineffective against established seedlings. Successful pre-emergent control can significantly deplete the seed bank in the soil.
If watergrass has already emerged, post-emergent selective herbicides are necessary to treat the active plants. Selective options, such as those containing quinclorac or fenoxaprop-p-ethyl, will target the watergrass while leaving the surrounding lawn relatively unharmed. These treatments are most effective when the watergrass plants are young. Always consult the product label to ensure the herbicide is safe for your specific type of turfgrass and follow all directions carefully.
Long-Term Strategies for Prevention
Preventing the return of watergrass relies on establishing a dense, healthy turf that naturally resists weed invasion. This involves correcting the underlying environmental factors that favor this moisture-loving weed. Improving soil drainage through core aeration helps break up compacted soil, allowing water to penetrate deeper rather than pooling near the surface.
Overseeding the lawn with desirable turfgrass varieties in the fall is a proactive measure that increases the overall density of the lawn. A thick, vigorous turf canopy physically crowds out weed seedlings, denying them the space and sunlight needed to establish. Using turf varieties that are well-adapted to the local climate will further enhance the lawn’s ability to compete.
Regular soil testing and proper fertility management are necessary to promote strong grass growth. Watergrass is a vigorous competitor for nutrients like nitrogen, potassium, and phosphorus. Supplying the lawn with the necessary nutrients, timed appropriately for the turfgrass species, ensures the desirable grass remains the dominant plant, making the environment hostile for future watergrass seedlings.