What To Do About Phragmites

— by Joan Treichel, SRA┬áScience Reporter

These willowy reeds with their wheat-colored plumes bending in the wind are an enticing view in the wetlands of the Chesapeake Bay and its tributaries.

But don’t let the reeds, officially called Phragmites australis, bewitch you!

While the species is native to North America, a European variety of the species is spreading rapidly across the US and southern Canada.

The European variety is invasive, can grow twice as tall as a human, and form stands that are as thick as a jungle.

It can out-compete native plants and displace animals. In the Maryland part of the Chesapeake Bay, the invader is rapidly invading freshwater and brackish tidal wetlands.

What to do about this challenge?

Half-a-dozen Maryland scientists and a colleague from Utah State University came together in a virtual workshop on the 1st of this month to discuss possible solutions.

Scientists participating in the workshop were Michael Allen, from the Maryland Sea Grant program, Eric Buehl, Regional Watershed Restoration Specialist with the University, University of Maryland graduate student Sylvia Jacobson, and her advisor, Dr. Andrew Baldwin, from the Department of Environmental Science and Technology.

They were joined by Drs. Melissa McCormick (at right) and Dennis Whigham of the Smithsonian Environmental Research Center located in Edgewater, Maryland, and Dr. Karin Kettenring, Professor of Wetland Ecology at Utah State University. They addressed key control challenges:

First: How to reduce Phragmites‘ population?

One approach is to reduce fertilizer (nitrogen) runoff into the Bay and its tributaries. Research by Kettenring, McCormick and Whigham has shown that the more nitrogen Phragmites receives, the more it grows.

20 Years Of Spraying Hasn’t Worked

Second: How to kill Phragmites?

Spraying herbicides and employing other eradication techniques such as fire, mowing, and grazing can reduce Phragmites, but research by the group of scientists has demonstrated that the Phragmites is likely to return.

Whigham pointed out that at a site that he and Jacobson have been treating with herbicides for 20 years, the invader still hadn’t been eliminated. “It is a difficult situation,” he said.

Third: How to remove Phragmites?

Removing Phragmites physically is quite effective, as is cutting and covering the site with heavy plastic.

But Whigham noted that it is hard to do these things over large wetland areas.

Dredging is another approach that can work, but it is an expensive proposition.

What About Native Replacements?

Finally: What can be done to restore a site with native plants? Once Phragmites removal has been achieved, how can you keep it from returning? To date, limited research has been conducted on this subject. Last year, the team initiated a project funded by the Maryland Sea Grant program to determine if an answer might be to jump-start restoration of a site by planting native species in areas where Phragmites have been removed.

They selected 12 sites in three tributaries flowing into the Bay — the Severn River, the Rhode River, and Parkers Creek (a small Bay tributary located in Calvert County) for a two-year experiment.

They then selected six native plant species to test, and planted them at each of the 12 sites. After the first year of the two-year experiment, they have found that although all of the species became established at one or more sites, growth varied from one site to another. There didn’t seem to be any winners at all of the sites.

Whigham noted that, “We are just ending the first year of our project,” and Baldwin indicated that next year “we hope to test more native plant species.”

An important aspect of the project is to provide information to managers as well as the public. “Perhaps we could offer some field trips next year so that the public could see what we are doing and to garner some interest,” Whigham proposed.

For more information, contact Dr. McCormick at mccormickm@si.edu or Dr. Whigham at whighamd@si.edu.