Non-Native Invasive Species

Common reed

Phragmites australis

Common reed

Canada thistle
Photo: Leslie J. Merhoff, University of Connecticut, Bugwood.org

Common reed, a taller-than-most-people member of the grass family (whose Latin name is Phragmites australis) is in beautiful, full tassel now, and will grow even more gorgeous as the tassels ripen and turn deep mahogany. Look for it in scattered locations on southern Vermont roads, highways, and abandoned industrial sites.

Look for it also in the New Jersey Meadowlands. Yup, that plant that near Giants Stadium covers hundreds of square miles - to the exclusion of nearly every other plant - is present in Vermont too. And though most things from New Jersey are good things, this isn't.

Common reed

Canada thistle
Photo: Jil M. Swearingen, USDI National Park Service, Bugwood.org

In fact, common reed isn't exactly from New Jersey. It seems to be from nearly everywhere, growing natively on every continent except Australia. Peat cores from northeastern bogs prove it was present in North America more than 3000 years ago, and ecologists wondered why a native plant should suddenly become aggressive. Research from the 1990s, however, shows that our native species is slightly different genetically from plants such as those that have crowded out all other life near Hackensack, that took over Kampoosa Bog on the Mass Pike, or that show up on Vermont Route 7A near the Wilcox farm in Manchester. They are more like European forms of common reed. And though the European form is in decline in Europe, here - for whatever reasons - it is highly invasive.

The invasive forms of common reed will grow in wet and dry locations, in alkaline or acid soils, in freshwater or brackish tidal marshes. But primarily, invasive common reed likes disturbed sites - lake edges, wet ditches, filled areas, gravel pits, park lands, and the like.

The plant moves as seed blown by the wind, but once established it reproduces vegetatively, from large, deep-running rhizomes. Huge mats of the plant soon develop, with thick layers of thatch on the soil surface that prevent colonization by other plants. Some song birds will use common reed for nesting sites, but most landscapes overtaken by the species are, compared to non-invaded landscapes, biological deserts.

Common reed

Canada thistle
Photo: Leslie J. Merhoff, University of Connecticut, Bugwood.org

Not surprisingly, once established common reed is hard to beat back. Most land managers who have to deal with it on a large scale use the herbicide glyphosate (trademark Rodeo™, for use in wet areas, or trademark Roundup™ for upland sites). To avoid damage to other plants (glyphosate kills most herbaceous species), some people cut the stems at a convenient waist height, then apply the herbicide inside the hollow stem using a large syringe (the sort of thing a large animal veterinarian might have).

For people who don't care for herbicides, simply cutting the stems in late July, year after year, will eventually drain the rhizomes of all reserves. Remove the cut stems, however. Left on site they might sprout again.