Phragmites: Occurrence and Management

Phragmites (Phragmites australis), or common reed, is a widely distributed reed grass found in coastal New Jersey. It is a wetland species that acts as a natural buffer against coastal erosion but is considered a major weed by property owners and developers throughout shoreline areas of the state. Phragmites has invaded lakes, ponds, and waterways, turning them into dry land. It also invades gardens and landscapes, where it suppresses biodiversity. It alters wetland habitats by displacing plant species that provide food for wildlife.

Phragmites is native to wetland areas, however the Eurasian lineage of the common reed is what has become dominant in marshes and swamps across North America. Native phragmites grows more sparsely and allows for undergrowth of other plant species, whereas the invasive lineage grows in denser and taller stands that crowd out other vegetation (Figure 1). It is abundant in brackish (slightly saline) areas but grows faster in freshwater environments. Phragmites is commonly found along railroad tracks, roadside ditches, piles of dredge spoil, any soil depressions that hold water, and other such disturbed locations. The expansion of this species has coincided with anthropogenic (man-made) alterations such as excessive nutrient inputs, dispersed hydrologic systems, and global climate change. Phragmites is able to reproduce rapidly by vegetative means through underground rhizomes, which forms a dense mat in the water bed (Figure 2). The seeds of invasive phragmites have poor viability, with less than 1% of seed growing to maturity in developed watersheds.

Mature plants may reach 6 to 9 feet in height, with leaf blades up to 2 feet long. From July to October, phragmites produces a pink-purple flower tassel, up to 1.5 feet in length (Figure 3). The tassel produces a large number of seed that is dispersed between November and January. Seed distribution is primarily through wind, birds, and human activities.

The underground rhizomes of phragmites can extend 6 feet deep into the soil, with the roots penetrating deeper. The underground parts thrive in stagnant water and can survive in water of between 1.2% to 3.9% salinity. For these reasons, phragmites thrives where few other plants can survive. The roots and rhizomes form dense mats that keep other plant species out of the ecosystem. The mat becomes a strong barrier for sediments and moving objects in the water medium by stabilizing and increasing marsh soil and preventing erosion. Positively, this attribute has been used favorably for wastewater management as phragmites sequester pollutants including nitrogen, metals, and carbon dioxide. Additionally, the roots and rhizome mat provide a habitat for some animals (for example, birds and muskrats) and insects (for example, gall and stem borers, and aphids) and acts as a food source for other wildlife from the accumulated plant detritus at the base of its stems.

Managing Phragmites

Biological Control

Biological control organisms are yet to be identified for phragmites control. Current research is ongoing to determine the effectiveness of eradication efforts.

Mechanical Control

1. Mechanical removal of leaf litter may increase phragmites stand density by exposing rhizome buds to light.
2. Burning does not offer complete control because rhizomes are not killed. Note that burning a phragmites stand can be dangerous since spot fires can be produced over 100 feet away. However, no one should conduct a prescribed burn without reviewing New Jersey's Prescribed Burning Policy and Procedure Guide for Private Landowners (PDF). A well-managed burning to remove accumulated leaf litter and dead biomass in winter, followed by tidal flooding, enhances control and cuts off oxygen to rhizomes. In spring, this will allow seeds of other plant species to germinate.
3. Cutting phragmites may also offer successful control. Timing is critical: Cut in June to impact aboveground and rhizome biomass. Repeat cutting for several years. Hedge trimmers and weed whackers cut well and perform better than loppers and sickles. Remove all cut stems to prevent re-sprouting.
4. Annual mowing only affects the above-ground plant parts. Continued mowing can gradually reduce populations of phragmites over time.
5. Suggestions for the home landscape:
   1. Phragmites rhizome biomass can be reduced significantly within 24 months by regular mowing with a standard lawn mower, followed by adding a thin layer of topsoil and seeding with a desirable turfgrass species. Mow every week to get results by the second year.
   2. Place clear plastic over the infested area during the summer, weighing the edges down. This creates high temperatures that induce plant dieback within 3 to 10 days. Phragmites may return, but the population will be significantly reduced. Black plastic cover from late summer through the winter has demonstrated up to 90% control of plants.
6. Other methods successfully used to reduce phragmites populations include:
   1. Grazing by cattle (rhizomes are trampled and lose vigor)
   2. Draining and dredging (not appropriate on preserves)
   3. Reintroducing saltwater tidal action (using a self-regulating tide gate)
   4. Flooding (3 feet of water must cover rhizomes during the 4-month growing season)
   5. Plugging of ditches and adding culverts to improve drainage and raise soil acidity
   6. Disking to expose rhizomes to desiccation. (Note that under favorable conditions, such as soils that are sandy and well-aerated, rhizome fragments may produce new plants).

Chemical Control

The use of any chemical control can have serious effects on nearby plants, animals, and ecosystems if used improperly. Any form of chemical control should be performed by an aquatic applicator business that has an up-to-date permit from the New Jersey Department of Environmental Protection's (NJDEP's) Bureau of Pesticide Control. Homeowners should check with NJDEP's Department of Aquatic Permitting to see if they need to obtain a permit before hiring a pesticide professional.

The recommended herbicides for phragmites control are glyphosate and imazapyr. For land application, it is sold as Roundup® (a concentrate) or Kleenup® (ready-to-use without mixing). These herbicides can also be sold as Rodeo® and Accord® for use in water or in wet areas. This herbicide is nonselective and will kill any live plant it hits. It is absorbed by the plant, translocates to the underground root and rhizome systems, and kills the plant. Within 7 to 10 days, the top vegetation growth yellows and dies.

Treatments should be applied in late summer (after tassels appear but before going to seed). The best results of herbicides are in occurrence with burning or mechanical methods. Do not apply under windy conditions to avoid drift. Do not apply if there is a chance of rain within 12 hours. Follow all label directions. Herbicides for phragmites control may be applied using air or ground sprayers, as well as wick wipers or backpack sprayers. Better results are obtained if old tassels are removed prior to herbicide application. If native phragmites is able to coexist while providing natural ecosystem services, it is recommended not to disturb.

References

1. Daniels, S. 1995. The Wild Lawn Handbook: Alternatives to the Traditional Front Lawn. Macmillan Publishing, 209 pp.
2. Derr, J. 1998. Personal communication.
3. Fairbrothers, D., E. Moul, A. Essbach, and D. Schallock. 1965. Aquatic Vegetation of New Jersey: Extension Bulletin 382. Rutgers Cooperative Extension, 107 pp.
4. Hazelton, E., T. Mozdzer, D. Burdick, K. Kettenring, and D. Whigham. 2014. Phragmites australis management in the United States: 40 years of methods and outcomes. AoB Plants. 6: plu001. Doi:10.1093/aobpla/plu001
5. Kettenring, K. and D. Whigham. 2009. Seed viability and seed dormancy of non-native Phragmites australis in suburbanized and forested watersheds of the Chesapeake Bay, USA. Aquatic Botany. 91(2009):199-204. Doi: 10.1016/j.aquabot.2009.06.002
6. Marks, M.B. Lapin, and J. Randall. 1994. Phragmites australis (P. communis): threats, management and monitoring. Natural Areas Journal. 14(4):285-294.
7. Michigan Department of Environmental Quality Water Resources Division. 2014. A Guide to the Control and Management of Invasive Phragmites (Third Edition). Michigan Department of Environmental Quality. 46 pp.
8. Neal, J., R. Uva, J. DiTomaso, and A. DiTommaso. 2023. Weeds of the Northeast (Second Edition). Cornell University Press, 608 pp.
9. Weis, J., E. Watson, B. Ravit, C. Harman, and M. Yepsen. 2021. The status and future of tidal marshes in New Jersey faced with sea level rise. Anthropocene Coasts. 4: 168-192. Doi: 10.1139/anc-2020-0020

Acknowledgment: This revised fact sheet is based on the original work of Deborah Smith-Fiola, Agricultural Agent, Ocean County, and Albert Ayeni, Extension Specialist, Weed Science.

September 2025