Delaware’s turf war

In nearly all of Delaware’s marshlands, plants native to Delaware are fighting a losing battle against a successful invader, the reed Phragmites.

 Spring’s explosion of growth brings with it a turf war. In nearly all of Delaware’s marshlands, plants native to Delaware are fighting a losing battle against a successful invader. This conquering weed is called Phragmites. Humans have long struggled to contain it, but recent budget cuts mean native plants are left to fend for themselves. Kerry Grens has more on what they are up against.

Radio transcript:

In ditches next to highways, in nature reserves and in suburban back yards — Phragmites is ubiquitous. The reed lives on land and in salt marshes. This time of year, new green shoots sprout near last year’s slender brown stalks, topped with feathery seed heads. The plant grows taller than a human, in thick stands that can span acres.

Bais: It’s there in almost 24, 25 states. But the midatlantic takes the maximum damage just because of the diverse nature of the habitats this plant can use.

Harsh Bais is a professor at the University of Delaware. By damage, he means invasion. Phragmites came to North America from Eurasia centuries ago. But in recent decades it has swept through wetlands, wiping out native plants. It forms dense stands connected underground by a thick root system called rhizomes. Bais says you can’t just pull Phragmites out like a garden weed.

Bais: They’re like highways underground of rhizomes that grow from here to several meters…You have to kill them by roots, that’s what it is. And it’s impossible just because how deep-rooted these plants are.

The plant chemically overpowers its native neighbors. Phragmites secretes a chemical called gallotannin from is roots. Bacteria or microbes in the soil then turn the gallotannin into a toxin, which kills nearby native plants. Bais’ laboratory discovered this sequence a few years ago, when it checked soil biochemistry in areas where Phragmites grows.

Researcher Amutha Sampath Kumar:

Kumar: We were shocked to find that with the exotics there were very high levels of gallotannins present when compared to the native species.

Phragmites shrugs off the presence of this toxin in the soil that kills native plants. Bais says there’s no good solution to this chemical turf war. Once Phragmites pairs with the microbes to produce the toxin, the chemical stays in the soil — making the soil sick, he says. Part of his research now is to find native plants that are also resistant to the toxin, hoping they can replace Phragmites after the plant is removed.

The man in charge of killing Phragmites in Delaware is Bill Jones at the Department of Natural Resouces and Environmental Control.

Jones: We actually started with Phragmites control in Delaware way back in the late 40s. Success was spotty until the 1970s, when Monsanto developed the herbicide Roundup.

Jones says Roundup has cut in half the 35,000 acres that Phragmites had usurped in Delaware.

Jones: We’ve helped to certainly reduce the coverage. Now, we tout it as a control program or management program. It’s certainly not an eradication program.

Farmer Chris Roberts has restored all but about 100 acres of the marshland on his property.

Roberts: What you would’ve seen would have been a total wall of Phragmites.

For the past three decades he’s participated in a cost-share program with the state to pay for herbicide spraying.

Roberts: Now we have the Phragmites under control and we have some blue bent coming back, we have some pipe reed coming back and it’s just working very well for us.

Until the money runs out. Funding for the cost-share program is on Govenor Markell’s list of budget cuts. Chris Roberts says he’ll continue spraying even without government help because the acreage involved on his land is now so small. But landowners new to the fight, dealing with hundreds of acres of thick Phragmites, might not stay in it.

 

Phragmites facts:

• Phragmites australis is an extremely invasive perennial reed, which physically overpowers wetlands across the country, including in Delaware, New Jersey, and Pennsylvania.

• Reaching heights of 15 feet, it blocks out light to neighboring plants, occupies all underground growing space with its extensive rhizome and root system (80% of Phragmites’ plant structure is underground), and uses allelopathy – the release of chemicals by one plant to inhibit the growth of another — to aggressively conquer and invade new territory.

• Recent research conducted in Delaware wetlands and at the Delaware Biotechnology Institute has shown that increasing ultra-violet light (a product of climate change) is increasing the “super weed’s” chemical effectiveness.

• Rhizomes — underground horizontal stems — make Phragmites highly adaptable to unfavorable conditions. When fragmented, rhizomes readily root and grow into new plants, far more readily than its seeds germinate, facilitating Phragmites’ rapid growth into dense uniform stands virtually impenetrable [pdf link] to wildlife habitation.

• According to The Environmental Protection Agency’s statistics [pdf link], nearly half of North American bird species nest or feed in wetlands; and although wetlands lay claim to only 5 percent of the land surface in the continental United States, they are home to 31 percent of plant species.

• Phragmites threatens the fragile balance of wetland ecosystems, lowering marsh plant and animal diversity. Phragmites displaces native plant species, thereby altering the water flow and water quality and reducing habitat for native animal species.
• Managing the spread of Phragmites [pdf link] requires multiple treatments using a combination of four methods : herbicide, controlled fire, mechanical removal, and water level management.

More info: USDA plant profile EPA wetlands page

Compiled by Anna Shipp