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Water chestnut (Trapa natans)
Photo credit: Conrad Kuiper/Flickr

Common Reed (Phragmites)

(Phragmites australis)

Report this Species!

If you believe you have found this species anywhere in Pennsylvania, please report your findings to iMapInvasives by submitting an observation record.

Species at a Glance

Phragmites is a perennial long-lived grass that can grow 1.8-4.6 m (6-15 ft) high in stands that exclude almost all other vegetation. While phragmites is native to North America, the introduction of a non-native strain from Europe rapidly and aggressively expanded throughout the United States, replacing much of the native reed.


Leaves: Broad, pointed, elongate leaves are typically 20-60 cm (7.9- 24 in) long and 1-5 cm (0.4-2 in) at their widest point. They arise from thick vertical stalks. Foliage is gray-green during the growing season.


Flowers: Bushy clusters called panicles grow 15-40 cm (5.9-16 in) long in late July and August. They are usually purple or golden in color, but as seeds mature the panicles begin to look “fluffy” due to hairs on the seeds, and they take on a gray sheen.


Stems/Roots: Rigid stems feel rough to the touch and reach 4.6 m (15 ft) in height next to dead stems from previous growth. Below ground, phragmites forms a dense network of roots several meters in depth and includes rhizome runners, which can grow 3 m (10 ft) or more in a single season.

Similar Species

Reed canary grass (Phalaris arundinacea) has a similar appearance to phragmites but is much smaller and has a membranous ligule. Giant reed (Arundo donax) also has a similar appearance and habitat but has a hairy lemma and a hairless spikelet stalk.


Phragmites is abundant along the borders of lakes, ponds, and rivers in tidal and nontidal brackish and freshwater marsh communities, roadsides, and disturbed areas. It does not tolerate rapidly moving water


Spread occurs mainly through vegetative means such as rhizome and stolon fragments. Rhizomes can break off and be washed downstream, becoming established in new areas. Phragmites also produces an abundance of wind-dispersed seeds, although seed viability is typically low. Heavy machinery may transport phragmites along roadsides between sites.


Invasive strains of phragmites, which were introduced in the late 1800s, are now widespread throughout the lower 48 states and southern Canada. It can be found in every Mid-Atlantic state.


Note: Distribution data for this species may have changed since the publication of the Mid-Atlantic Field Guide to Aquatic Invasive Species (2016), the source of information for this description.

Environmental Impacts

Dense stands of invasive phragmites can crowd out native plant species, alter marsh hydrology, alter wildlife habitat, and increase fire potential. It blocks light to other plants and emits a toxin that allows it to outcompete native species, quickly turning once biologically diverse wetlands into monocultures.


Information for this species profile comes from the Mid-Atlantic Field Guide to Aquatic Invasive Species (2016).

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