Picture 7,000 acres of only one plant. That is equivalent to nearly 11-square miles and is the area of one of the largest infestations of Phragmites australis (common reed grass). New Jersey carries that unfortunate claim to fame. Luckily, most infestations in the Adirondack region are on the scale of one acre or smaller. But even small populations, if left untreated, will spread to uncontrollable levels. Two Phragmites stands in a wetland near Saranac Lake multiplied to nine stands in six years. Unfortunately this type of spread is starting to happen all over the region.
A tall, perennial grass with erect stems, Phragmites is listed as one of the world's 100 worst invasive species. Invading freshwater and brackish wetlands, it is widely distributed, ranging all over Europe, Asia, Africa, America and Australia. However, the origin of the species is unclear. Some scientists link the species that is invasive here to a European variety which has been spreading for the last 150 years.
Plants can grow in damp ground, in standing water or even as a floating mat. They typically first become established along roadsides because of accidental introductions by machinery or infected soils used during maintenance or construction projects. Over time, the population grows and bleeds into marshes, pushing out native grasses, sedges, rushes and other native wetland plants.
Phragmites australis (common reed grass) is an aggressive wetland invasive plant that grows to 15 feet or more in height.
(Photo — Adirondack Park Invasive Plant Program)
Spread is usually due to underground root growth or fragmentation. Later in the summer, Phragmites forms plumes of purple to brown flowers, which produce seeds. Seeds can be dispersed by the wind, water or birds, but its roots are the primary cause of spread. Where conditions are suitable, it can spread 16 feet or more per year.
Native Phragmites grows here too, though it is far less common and not problematic. Distinguishing between the two can be tricky, but the native species generally has a reddish color along the lower part of its stem. Also, its long blades of leaves typically fall off in autumn, while the dead leaves of the invasive species tend to remain attached. More often than not, the population one sees will be the invasive one because it has eliminated many of the occurrences of its native equivalent.
Since the plants are so similar in appearance, what makes native Phragmites beneficial and the non-native less so? Density. Native Phragmites grows sparingly and is intermixed with other native vegetation. Non-native Phragmites grows so vigorously that other plants cannot compete. Size. Native Phragmites grows to heights of 6 to 8 feet; non-native reaches heights double that.
Growing to 15 feet or more, Phragmites forms impenetrable thickets. Its tall canes form a wall of dense, above ground plant material; below ground its rhizomes develop a deep, thick mat of roots. The canes usually remain upright through the winter and are pushed over as new growth emerges in the spring. As plants decompose, they release toxins that poison susceptible vegetation and seedlings.
Besides eliminating native wetland plants, Phragmites also ruins the quality of habitat for birds, waterfowl and other wildlife. Studies have shown that fewer bird species, such as marsh wren, American goldfinch and song sparrow, utilize wetlands invaded by Phragmites.
Sometimes people think that Phragmites is native or is intentionally planted because it is so prevalent across the state. Actually, its widespread distribution illustrates how aggressively this plant spreads.
The Adirondack Park Invasive Plant Program (APIPP) maps locations of infestations across the region and manages those in priority natural areas. If you see Phragmites or if you need information about control methods please contact APIPP at 518-576-2082.
Eye on Invasives is a biweekly column that spotlights a top invader when it is easiest to identify. Hilary Smith directs the Adirondack Park Invasive Plant Program, a partnership program housed at the Adirondack Chapter of The Nature Conservancy in Keene Valley, NY. Find out more about this award-winning program online at www.adkinvasives.com.