The common reed, Phragmites australis, is a non-native perennial grass that has established itself globally, particularly dominating wetland and disturbed areas. This invasive plant forms dense, monocultural stands that choke out native vegetation, reduce local biodiversity, and impede water flow. Its rapid spread and massive underground root network make its removal a significant challenge, demanding persistent and targeted control strategies. The difficulty in eradication stems from the plant’s biology, requiring a well-planned, multi-year approach rather than a quick fix.
Identifying the Invasive Common Reed
Confirming the presence of the invasive subspecies, Phragmites australis ssp. australis, is the necessary first step before implementing any removal plan. This tall, stout grass commonly reaches heights of 10 to 15 feet, distinguishing it from most other wetland vegetation. The stalks are rigid, rough in texture, and typically tan or dull light green, persisting through the winter months. The plant produces dense, feathery seed heads, called panicles, which are usually purplish-brown and often last until the following spring. Below the surface lies a massive network of horizontal underground stems known as rhizomes. These rhizomes store vast energy reserves, allowing the plant to rapidly regenerate and making simple cutting or pulling ineffective.
Non-Chemical Removal Methods
For smaller, isolated patches or in sensitive areas where herbicide use is restricted, physical methods can be used, but they require persistence. Cutting or Mowing is the most common non-chemical approach, but it must be repeated multiple times throughout the growing season for several consecutive years to deplete the rhizome energy stores. Stalks should be cut to a height no taller than four inches above the ground, and all cut debris must be removed from the site to prevent re-establishment from fragments.
If the plants are growing in water, cutting the stems below the waterline is a more effective technique, often called “cut-to-drown.” This method starves the plant of oxygen, as Phragmites relies on its hollow stems to transfer oxygen to its extensive root system. The cut stems must remain fully submerged, as the plant can “snorkel” for oxygen if any part of the leaf or stem is above water.
Smothering involves covering the entire patch with heavy-duty black plastic or specialized mats to block sunlight and prevent photosynthesis. This process is slow, often requiring the material to remain in place for one to three full growing seasons. Excavation, or digging out the rhizomes, is only feasible for very small, new infestations. The rhizome network can extend up to ten feet deep, meaning any attempt at digging must ensure the removal of all root fragments, as the plant can regenerate from even small pieces.
The Integrated Approach: Timing and Chemical Application
For large or well-established stands, an Integrated Pest Management (IPM) approach combining physical methods with chemical control is necessary. This strategy hinges on preparing the plant for herbicide treatment, which maximizes the absorption and translocation of the chemical. Chemical application is most effective in late summer or early fall, typically from mid-August through October.
During this late-season period, the plant is no longer actively growing new shoots but is instead translocating its sugars and nutrients down to the rhizomes for winter storage. Applying a systemic herbicide at this time allows the chemical to be pulled deep into the underground rhizome network along with the sugars, effectively killing the plant’s energy reserves. This translocation process makes late-season treatment superior to spring or mid-summer applications.
The most common and effective herbicides for Phragmites contain the active ingredients glyphosate or imazapyr, both of which are systemic and non-selective. If the infestation is near a water body, it is necessary to use an aquatic-approved formulation of these herbicides to protect fish and other aquatic life. Imazapyr is considered more effective due to its longer residual activity in the soil, although it requires greater caution to avoid harm to desirable plants.
If physical cutting is incorporated into the chemical strategy, it should be done to prepare the site and remove dead biomass, but not immediately after spraying. Mowing or cutting should occur at least two to three weeks after the herbicide application to ensure sufficient time for the chemical to translocate fully down to the rhizomes. Eradication is rarely achieved with a single chemical application, so long-term monitoring and follow-up spot treatments are required for several years. Once control is achieved, the final stage involves revegetation with native species to prevent the Phragmites from recolonizing the cleared area.