Feature Article: Invasive Phragmites australis is Detrimental to Our Wetlands

By Larry Meyer  

For invasive Phragmites australis, early detection and eradication is a must to save money, save time and keep our wetlands healthy. Phragmites australis is an invasive plant that grows 12 to 16 foot tall, with twenty-foot lateral root systems of rhizomes or stolon, with plant numbers doubling or tripling in size every year. If not detected in the first year and eradicated, problems with Phragmites australis get more expensive, more time-consuming, and complete eradication is not guaranteed as extensive root systems develop quickly, storing energy. Many landowners give up because of the expense and time-consuming work, and the problem just continues to grow. Phragmites also spread by seeds to other wetlands crowding out native vegetation, which is detrimental to fish and wildlife like ducks, shore birds, muskrats and any wildlife that counts on wetlands for survival.  

If you own property with wetlands or know someone near you that does have a wetland or any spot that may hold moisture, ditches, wet fields, and there is no Phragmites australis growing on it; consider yourself lucky. Phragmites australis is spreading rapidly across Wisconsin, with high concentrations near Lake Michigan and the southern part of the State. A lot of state wildlife areas have a problem with Phragmites australis, and they cannot afford the time and expense to eradicate it.  

To prevent Phragmites australis in wetlands, you must patrol your wetlands for phragmites a couple times a year in late May and again in August. Early detection when a few plants are just starting, is the time to eradicate it. There is a native Phragmites americanus that does not grow as thick, with smaller seed heads and reddish stems in the late summer. But during early detection it is hard to tell the two phragmites plants apart. My recommendation is to, if in doubt, eradicate the plant, and let other native plants grow in its place. To miscalculate Phragmites australis could be very costly to the wetland. 

There are two methods you can use to eradicate new plants. Some wetland owners do not like using chemicals. The first method is to take a sharp spade and cut in near the base of the stem, cutting off the plant underground. Try to disturb the soil as little as possible. Step on the ground where the stem was at, to compact the soil. This mechanical method is to prevent photosynthesis, smothering the new root system. Remove the cut plants from the wetland. If you leave the cut plants on site, new plants can sprout from rhizomes or seed. Mark the site with a stake and flag. You can use this method where Phragmites grow in water at least one foot deep. Check the site again. Phragmites australis is a difficult plant to control and will likely take multiple years to control. If the plant is growing again, you can continue to try to control mechanically or apply Imazapyr herbicide. If you choose to apply herbicide, bundle the stems together using a piece of twine, cut and bag the top of the plant. Follow label directions and apply Imazapyr only to the new cut stems. Imazapyr (some brand names are Polaris, Habitat, Arsenal, Chopper, Stalker) will go into the root system and kill the young plant. 

For Phragmites australis plants growing in water more than one foot deep, you can cut the plant by using a cane cutter at the base of the plant. Always collect the stems and remove them from the wetland, as stems and cut plants can grow and start a new patch of phragmites.

If you decide to try eradicating a large established patch of Phragmites australis, try to prevent the patch from spreading by killing the plants on the outskirts of the patch first, then cut off and collect the seed heads. If there is moving water, public waters, you may need a WDNR permit to apply chemicals. You may need a three-to-five-year plan to eradicate all the plants.  

We wish you the best in eradicating Phragmites australis before it gets out of control.  For additional information on Phragmites australis see the WI DNR’s page on the invasive or the Phragmites Statewide Management Strategy document.