Phragmites australis is an impressive grass
Driving down Route 95, just south of the traffic circle, wetlands full of common reed stretch as far as the eye can see. I particularly love driving by these wetlands at sunrise, the light shines through the tall grasses, illuminating the seed plumes so they shine like fire. These are fields of an invasive species - the European common reed - Phragmites australis.
I was out at Plum Island (the Parker River National Wildlife Refuge in Newburyport, Massachusetts) this weekend birding in the deep marsh, walking along boardwalks through marsh grasses so tall you couldn’t see over them. They filled the whole marsh. We stopped at Station 5 of the Marsh Loop, at a sign that talked about invasive species in the marsh: “Phragmites australis is a plant that invaded this and other wetlands of the Northeast. This invasion has diminished the wildlife, food and protective cover values of marsh habitats by displacing native plant species.” The Refuge has been working on controlling Phragmites since 1959, not very successfully….it turns out that this lack of success is fairly common throughout the United States, scientists are still researching and developing effective control methods.
Phragmites is an impressive grass — it can grow to over 15 feet tall! The name “Phragmites” comes from the Greek “Phragma” meaning fence. A stand of Phragmites does indeed form a fence with its dense growth. In North America there are both native (very uncommon) and introduced subspecies that are extremely difficult to tell apart.
Introduced Phragmites is notorious for forming dense stands that exclude native species. The flowers form bushy ‘panicles’ (panicles are branched inflorescences-the flowers of grasses). The panicles of Phragmites are beautiful—many-branched plumes. They look fluffy because of the hairs on the seeds. One stalk of Phragmites can produce up to 2,000 seeds per seed head (panicle) per year! These seeds are the predominant mode of seed dispersal. The big problem with Phragmites is how quickly it can take over a salt marsh or freshwater cattail marsh. Once introduced, Phragmites can invade a site very quickly - it crowds out native plants, changes the hydrology of the marsh, makes salt marshes less salty, builds up the marsh and increases the fire potential. It forms a dense network of underground roots and rhizomes - the rhizomes can grow 10 feet or more in a single growing season - it can turn a diverse marsh ecosystem into a Phragmites monoculture very quickly.
According to the National Park Service: “Introduced Phragmites is thought to have arrived in North America accidentally, most likely in ballast material in the late 18th or early 19th centuries. It established itself along the Atlantic coast and over the course of the 20th century spread across the continent.” Interestingly, in Europe Phragmites is a useful commodity and is grown commercially for thatching, fodder for livestock, and cellulose production. Unlike what is happening here, where we don’t want it, Phragmites is declining in parts of Europe most likely as a result of habitat degradation.
The only positive attribute I have found about the invasive form of Phragmites in North America is its ability to build a marsh. According to research from the University of Maryland’s Center for Environmental Science Phragmites has double the rate of accretion (gradual buildup) of other marsh grasses, this is good because it keeps time with sea level rise. Sea level rise, if it happens too quickly, as it is in the Gulf of Maine, can inundate and destroy a salt marsh; Phragmites can keep that from happening. So, in the end, while we will suffer from the loss of diversity of our coastal wetlands, at least we might still have them.
