How to Identify Native and Introduced Phragmites

Phragmites australis subsp. americanus. Photo taken in early August in southern Minnesota.

Update: An abbreviated ID guide (PDF) is here. 

Phragmites or Common Reed, Phragmites australis, is a 12- to 18-foot tall, perennial grass of wetlands, shorelines and ditches. Two subspecies are common in the U.S. One is the native subspecies americanus; the other is the introduced subspecies australis.

Both subspecies grow in colonies, but subspecies australis is more aggressive and can dominate habitats to the near exclusion of other plants. For that reason, there is growing interest in identifying and mapping subspecies australis to determine the extent of its spread and to target those colonies for removal.

Although the subspecies look alike, there are several characteristics that, taken together, can identify one from the other. The most reliable characteristics are shown below, after a few terms used to describe grass stems, leaves and flowers.

Stems and leaves

The culm is the stem of a grass. Grasses have round culms that are hollow between the nodes, the swollen areas on a culm. The leaf blade is flat and ribbon-like, whereas the leaf sheath wraps around the culm below the blade. Where the blade meets the sheath, most grasses have a ligule, a membrane or hairy fringe visible when the blade is pulled away from the culm.

Flowers

Grass flowers, called florets, are specialized for wind pollination. Each floret is composed of two narrow bracts, a lower lemma and an upper palea. Stamens and feathery stigmas emerge from between them.

Florets are arranged in small spikes called spikelets. At the base of each spikelet are two bracts called glumes. Glume length differs between the subspecies of Phragmites. More on that in a following section. 

Spikelets of Smooth Brome, Bromus inermis, are shown below. On the left are spikelets with brown anthers and feathery, white stigmas emerging from individual florets. On the right is a single spikelet spread apart to see the florets and glumes. The spikelets are about  3 cm (1.5 in.) long. 

Phragmites characteristics

To identify Phragmites subspecies, it’s best to look at more than one plant in a colony and at several characteristics of each plant. Hybrids are possible, but they’re said to be rare. 

Ligules 

To see ligules, pull back a blade from the middle third of the culm. (Ligules may be immature on the upper third of the culm and degraded on the lower third.) Ligule length differs between the subspecies. 

Subspecies americanus: 1-2 mm long, brown, become darker and smudgy in late summer and fall. The photo below was taken in early August.

Subspecies australis: 0.5-1 mm long, appearing as a thin, brown line. The photo below was taken in early July.

Stem color and texture

In summer and fall, examine the base of the culm. Be sure to look at the culm and not the sheath, if one is present. The photos below are from early July.

Subspecies americanus: Lower culm is smooth, somewhat glossy, often red.

Subspecies australis: Lower culm is ridged, not glossy, often green fading to brown.

Sheaths

In late summer, fall and early winter, examine the lower stem for the presence of leaf sheaths. The photos below are from mid-November.

Subspecies americanus: Sheaths are absent or easily removed.

Subspecies australis: Sheaths are persistent and harder to remove. 

Glumes

In late summer and fall, measure glume length. By late fall some of the florets may be gone, but the glumes often persist. It's best to look at several pairs of glumes to get an idea of their average length. The photos below are from mid-November.

Subspecies americanus: Lower glume 3-6 mm long (most > 4mm); upper glume 5-11 mm long (most > 6 mm).

Subspecies australis: Lower glume 2.5-5 mm long (most < 4 mm); upper glume 5-8 mm long (most < 6 mm).

Panicles

In late winter, spring or early summer, look at last season's panicles, the plume-like clusters of Phragmites spikelets. The photos below are from early July.

Subspecies americanus: Panicles bare, thinner, less branched.

Subspecies australis: Panicles fuzzier, thicker, more branched.

Look-alikes

Amur Silver Grass and Reed Canary Grass are two smaller grasses that can be mistaken for Phragmites. 

Amur Silver Grass, Miscanthus sacchariflorus, is an introduced grass that has silvery-white panicles in late summer and fall. It grows 6-8 feet tall, shorter than Phragmites, and its leaf blades have a white midrib. Its ligules are a greenish-white, hairy fringe. The photos below were taken in early August.

Amur Silver Grass plants and ligule.

Reed Canary Grass, Phalaris arundinacea, blooms in spring, not late summer, with smaller panicles that eventually contract. It's shorter than Phragmites, growing up to 5 feet tall. Its ligules are membranous and 3-8 mm long. 

Reed Canary Grass colony and ligule.

References

Chadde, S.W. 2012. Wetland Plants of Minnesota. 2^nd edition (revised). A Bogman Guide.

Judziewicz, E. J., Freckmann, R.W., Clark, L.G., and Black, M.R. 2014. Field Guide to Wisconsin Grasses. The University of Wisconsin Press, Madison.

Minnesota Aquatic Invasive Species Research Center (MAISRC). Identifying invasive Phragmites. Website accessed July 2022.

Swearingen, J., Saltonstall, K., and Tilley, D. Phragmites Field Guide: Distinguishing Native and Exotic Forms of Common Reed (Phragmites Australis) in the United States. Technical Note Plant Materials 56, October 2012. USDA Natural Resources Conservation Service, Boise, ID.

Plant profile: Enchanter's Nightshade

 

Enchanter's Nightshade, Circaea lutetiana L., in July. 

Enchanter’s Nightshade, Circaea lutetiana, doesn’t get a lot of positive attention. This native plant of the forest floor is often regarded as a weed, something to remove in favor of less aggressive, more attractive species. Its appearance is modest at best. Its name, though, suggests something less humble. What’s the story?

Mostly Inconspicuous

Compared to showier spring wildflowers, this summer bloomer isn’t much to look at. Individual stems grow up to a foot tall, sometimes longer, with opposite, egg-shaped leaves and smooth stems. The plant spreads with rhizomes to form colonies, especially in disturbed areas or canopy gaps where more light reaches the understory.

In July and August, Enchanter’s Nightshade produces small, white flowers on racemes. If not for their masses, the flowers would be easy to miss. Each is just a few millimeters across, smaller than an eraser on the end of a pencil, with a mere two sepals, two petals, two stamens and one pistil. They're beautiful, but minimal. 

Small, pear-shaped fruits follow. They’re covered with hooked hairs that grab onto anything that passes – shoelaces, socks, pants, fur. It’s impossible to ignore them, but it’s not the kind of attention that inspires admiration. A few steps through a patch catches a load of little stickers.

Flowers and fruits of Enchanter's Nighshade.

From Meek to Mythical

The ”enchanter” in the plant’s name is Circe, the sorceress of Greek myth. According to legend, she used herbs and potions to turn people into pigs, lions and wolves. One of the herbs in her concoctions was Circaea lutetiana, the plant that now bears her name. The species name lutetiana also reflects the plant’s supposed use in sorcery. Lutetia was the ancient city that is now Paris, France, called “the city of witches” in some accounts.

Studies of the plant’s chemistry don’t find much that is bewitching. Although it’s called a nightshade, it’s not a traditional member of that group. Nightshades are usually plants in the tomato family, Solanaceae (solan-AY-see-ee). In terms of chemistry, this family is known for its higher quantities of alkaloids, compounds that have uncertain roles in plants but a variety of physiological effects in humans. Some alkaloids, such as opium from poppies and cocaine from coca bushes, are mind-altering, euphoric and addictive.

In contrast, Enchanter’s Nightshade is in the evening primrose family, Onagraceae. Its chemistry features flavonoids, molecules that have various functions in plants. Some are pigments – the red of raspberries, for example – while others regulate growth or protect against UV radiation, among other roles (1, 2). Like alkaloids, flavonoids have potential use in medicine, but they aren’t mind-altering, and they aren’t associated with euphoria. In fact, they’re relatively benign. Circe might have worked some legendary magic, but Enchanter’s Nightshade wouldn’t have put much punch in her potions.

Adaptation and Potential Advantage

The ”nightshade” in its name, then, probably comes from its shady habitat. Like other plants of the forest floor, Enchanter’s Nightshade is adapted to an environment with limited light. One adaptation is its ability to colonize gaps or disturbances by growth if its rhizomes, underground stems that produce shoots along their length.

Unlike other clonal plants, Enchanter’s Nightshade holds some of that ability in reserve. Its new rhizomes do not produce shoots. Instead, they lengthen and branch until late summer, when some of them produce small tubers called hibernacles at their tips. Eventually the hibernacles are separated from the parent plant and from each other and go dormant. They are the vegetative equivalent of seeds, but with faster development the following spring to form patches of upright stems. In higher light intensities, this growth can be vigorous (3). 

Near the end of the season, tips of rhizomes (arrow) develop into tuber-like hibernacles.
The hibernacles overwinter and resume growth next spring, forming new rhizomes and
above ground shoots.

Although some consider that growth weedy and aggressive, it could prove useful. Restorationists are looking at Enchanter’s Nightshade and other “weedy natives” as potential cover crops where severe infestations of invasive plants have been removed. By shading out or otherwise competing with invasive plants that can reoccupy an area, Enchanter’s Nightshade may give native communities an improved chance to recover (4). 

It’s not magic, but it could be transformative. If research shows this to be an effective restoration technique, Enchanter’s Nightshade could help convert a landscape from diminished to diverse. 

References

(1) Falcone Ferreyra, M.L,  Rius, S.P., and Casati, P. (2012). Flavonoids: biosynthesis, biological functions, and biotechnological applications. Frontiers in Plant Science volume 33, article 222. https://doi.org/10.3389/fpls.2012.00222.

(2) Panche, A. N., Diwan, A. D., and Chandra, S. R. (2016). Flavonoids: an overview. Journal of nutritional science, 5, e47. https://doi.org/10.1017/jns.2016.41

(3) Verburg, R.W., and During, H.J. (1998). Vegetative propagation and sexual reproduction ­in the woodland understorey pseudo-annual Circaea lutetiana L. Plant Ecology 134: 211-224. https://doi.org/10.1023/A:1009741102627.

(4) Reinartz, J., White, M., and Hapner, J. No date. A role for native weeds and aggressive plants for replacing (or competing with) invasives in badly degraded areas. Invasive Plants Association of Wisconsin. Accessed online on 7/13/22 at A Role for Native Weeds - Invasive Plants Association of Wisconsin (ipaw.org).