The pervasive wetland plant often referred to as “water reeds” is, in most cases, the invasive species known as Phragmites australis, or the Common Reed. While this tall grass is a cosmopolitan species found worldwide, the non-native subspecies, largely introduced from Eurasia, poses significant problems in many ecosystems. It is a perennial plant that spreads rapidly through an extensive network of underground stems, or rhizomes, giving it a remarkable capacity for colonization. Its aggressive growth and ability to thrive in disturbed environments make its management a complex and long-term undertaking.
Identifying the Common Reed
The non-native Phragmites australis stands out due to its substantial height, often reaching between 10 and 16 feet tall, far exceeding many native grasses. The stems, or culms, are typically dull greenish-tan and have a finely ribbed, rougher texture compared to the smooth, reddish stems of its native counterpart. Leaves on the invasive variety present a distinctive bluish-gray-green hue and remain tightly attached to the stem throughout the growing season.
The most noticeable feature in late summer is the dense, bushy flower head, known as a panicle, which ranges in color from purplish-brown to grayish. These plumes can be 6 to 15 inches long, eventually developing a fluffy appearance as seeds are dispersed by the wind. Identification is further confirmed by examining the extensive root structure, which forms a dense mat of rhizomes that can extend several feet deep and horizontally, allowing the plant to form large, impenetrable stands.
The Ecological Impact
The dense colonies of Common Reed are problematic because they severely reduce the biodiversity of wetland and shoreline areas. By forming thick, single-species stands, Phragmites crowds out and displaces native wetland vegetation, including important food sources for wildlife. This reduction in plant diversity directly degrades the habitat quality for numerous species, including nesting waterfowl, fish, and various amphibians.
The plant’s massive accumulation of dead stems and leaves, known as standing litter, decomposes slowly, which can alter the natural nutrient cycling within a wetland. Furthermore, the dense growth can impede water flow, leading to changes in hydrology that may result in increased sedimentation or localized flooding. Some research also suggests that the plant engages in allelopathy, releasing chemicals from its roots that actively inhibit the growth of surrounding plant species.
Non-Chemical Management Methods
Effective non-chemical control of Common Reed requires persistence and often involves combining several mechanical and physical techniques. Simply mowing or cutting the above-ground biomass is rarely successful on its own and may even stimulate denser regrowth if not timed correctly. Mechanical removal is generally used as a preparatory step to facilitate other treatments or to remove accumulated dead stems.
One highly effective physical method, particularly in areas with standing water, is the “cut-to-drown” technique. This involves cutting the stems well below the waterline, typically during the peak growing season from mid-spring to mid-fall. Severing the stems underwater cuts off oxygen from the extensive rhizome system, effectively drowning the plant over time. This technique is most successful when the plant is actively growing and transferring energy.
Water-level manipulation, or flooding, is another non-chemical option where the site hydrology can be controlled. The strategy involves maintaining water depth at a minimum of 5 feet for at least six weeks during the late summer to stress the plants and prevent oxygen intake. For very small, localized infestations, manual removal methods like “spading,” which involves using a sharp tool to sever the stem and rhizome just below the soil surface, can be employed. Regardless of the method, repeated treatment over multiple seasons is necessary to exhaust the plant’s significant energy reserves stored in its rhizomes.
Prescribed burning is a tool used not for primary control but rather to remove the dense layer of dead biomass. Burning creates a clear surface that makes subsequent herbicide application or spot-treatment of regrowth easier. Due to the intensity of the fire produced by the dry, hollow stalks, this technique must be conducted only by trained professionals and requires appropriate permits.
Chemical Control Strategies
Herbicide application is frequently considered the most effective initial step for managing large, dense infestations of Phragmites australis. The timing of the application is important to ensure the chemical is successfully transported to the root system. Herbicides should be applied in the late summer or early fall, generally between August and the first hard frost, when the plant is actively moving sugars and nutrients downward into the rhizomes for winter storage.
The most common herbicides used for this purpose are aquatic-approved formulations of glyphosate and imazapyr, as general-use products are restricted near water bodies. Glyphosate is a non-selective herbicide that kills most plants it contacts, while imazapyr offers soil residual activity and may pose a greater risk to non-target plants in the soil. Strict adherence to product labels, particularly those requiring aquatic formulations, is mandatory to protect the surrounding environment.
Application can be achieved through foliar spray for widespread coverage, though care must be taken to minimize drift onto desirable species. For smaller, isolated patches, a more targeted method, such as the cut-and-pour technique, is often preferred. This involves cutting the stem and applying a concentrated herbicide solution directly into the hollow culm, which moves the poison straight to the rhizomes with minimal risk of environmental contamination. Due to the complexity of application near wetlands, consulting with or hiring a licensed professional applicator is frequently recommended for successful long-term control.