The term “water grass” describes a range of unwanted plant growth that thrives in saturated environments, from decorative ponds to residential lawns. Because this term is non-specific, identifying the environment and the exact plant species is the first step toward successful eradication. Effective removal depends on whether the plant is a true aquatic species or a terrestrial weed flourishing in excessively wet soil. Understanding this distinction allows for the selection of appropriate, targeted control measures, which differ significantly between water bodies and turfgrass.
Clarifying “Water Grass”: Aquatic vs. Terrestrial Weeds
“Water grass” commonly refers to two distinct categories of vegetation, each requiring a different management approach. True aquatic weeds live primarily within the water column of a pond or lake, such as floating species like duckweed and water hyacinth. Submersed varieties, including curlyleaf pondweed or filamentous algae, root in the sediment or float freely.
The second category includes terrestrial weeds that aggressively colonize areas with poor drainage and perpetually moist soil, often found in lawns or gardens. The most common is nutsedge, which is botanically a sedge, not a true grass, and is often misidentified as “nutgrass.” Nutsedge can be distinguished by its triangular stem, unlike the round stems of actual grasses, and its preference for saturated turf.
Eradication Strategies for Aquatic Weeds
Managing unwanted growth in ponds and lakes requires careful consideration of the entire aquatic ecosystem. Physical removal is one option, involving mechanical harvesting, hand-pulling, or specialized rakes to remove large masses of vegetation. For localized control, a benthic barrier, a material placed on the pond bottom, can smother rooted plants by blocking sunlight.
Biological control introduces natural predators to manage the weed population. The sterile triploid grass carp is an effective herbivore for controlling many submersed vascular weeds. Introducing these fish often requires permits from local environmental agencies and is non-selective, meaning they consume desirable vegetation along with the weeds.
For chemical control, only aquatic-labeled herbicides registered with the Environmental Protection Agency (EPA) should be used, such as those containing diquat or fluridone. Algaecides, typically containing copper sulfate, are effective against various forms of algae. A risk of chemical treatment is the rapid death and decomposition of large amounts of plant matter, which can severely deplete dissolved oxygen and result in fish die-offs.
Control Methods for Wet-Area Lawn Weeds
Weeds like nutsedge, which thrive in soggy lawns, require herbicides specifically formulated for sedges, as standard broadleaf or grassy weed killers are often ineffective. Selective post-emergent herbicides containing active ingredients like halosulfuron or sulfentrazone are necessary to target these plants without harming the surrounding turfgrass. These products work best when applied while the sedge is actively growing, typically in its three-to-eight leaf stage.
Attempting manual removal often worsens the problem because nutsedge reproduces via underground tubers, called nutlets, and rhizomes. Pulling the visible plant can leave these nutlets behind, stimulating new shoots from the dormant tubers. When dealing with an established infestation, a targeted application of the correct herbicide is necessary to translocate the chemical down to the root and tuber system for complete control.
Adjusting the mowing height can offer some competitive advantage to the turf. Maintaining a taller lawn helps shade the soil surface, making it less hospitable for nutsedge to germinate and establish itself. This cultural adjustment, combined with chemical treatment, provides a better chance of reducing the visible weed population.
Cultural Practices to Limit Regrowth
Long-term weed control focuses on changing the environment to make it unfavorable for the problem plants. In a lawn setting, this means addressing the underlying poor drainage that allows weeds to flourish. Techniques such as core aeration, amending the soil to improve its texture, or installing French drains can reduce soil saturation and make the area less attractive to wet-loving weeds.
Adjusting irrigation practices is also a preventative measure, as consistent overwatering creates the saturated soil conditions nutsedge prefers. Watering deeply but less frequently encourages deeper turf roots and allows the soil surface to dry out between applications. For aquatic environments, prevention centers on limiting the two main resources weeds need: nutrients and sunlight.
In ponds, non-toxic pond dyes can be applied to tint the water blue or black, effectively blocking the sunlight required for submersed weeds to photosynthesize. Nutrient reduction can be achieved by establishing vegetative buffer strips along the shoreline, which intercept fertilizer runoff from the surrounding land. Additionally, introducing beneficial bacteria can help consume excess organic matter and nutrients, reducing the available food source for algae and aquatic weeds.