Distinguishing native from non-native Phragmites australis can be challenging. Here we provide guidance to assist you in making this distinction. The morphological characters presented here are in order of stronger characters to weaker characters. Characters most readily identifiable in the field are leaf sheath adherence to the stem and stem glossiness. These characters are best used after mid-summer and in winter. Ligule height can be a strong character, but using it in the field requires a little bit of practice. Stand density, stem height, leaf color, and inflorescences are variable characters that are not reliable on their own for identification. A solid ID depends on using 3-4 different characters. Information is provided here on each of these characters to provide additional context for distinguishing native from non-native Phragmites.
Report populations of suspected non-native Phragmites in the EDDMapS Pro app. Your report should include several photos. Include an image of the whole stand, as well as details of the leaf sheaths, stem color/texture, close-up of the ligule, and inflorescences.
Grass vegetative structures
Leaf adherence to stem
In early to mid summer, the leaf sheaths on the upper stems of native Phragmites are also tightly adhering. Lower sheaths may be somewhat loose, but may not gap yet. Note that the sheaths of native Phragmites, particularly on the lower stems, do not consistently overlap each other and the stem is exposed in the gap between the two adjacent sheaths. In early summer, the stems will already be red where they are not covered by the sheath and they will be smooth and shiny.
The sheaths of non-native Phragmites more consistently overlap each other, so the stem appears to be more consistently green. Sometimes on the lower stem, the sheaths do not overlap, and where the stem is exposed, it may have a reddish blush. This seems to be more typical of young stems and stems growing in standing water. Where the stem is exposed, it will be dull and rough, as described below.
Stem texture and color
Ligule height (thickness)
Ligule height (thickness) is one of the stronger characters for identifying non-native Phragmites. Although it may not be easy to measure in the field, it can be visually determined with a little practice using the cues described here.
Measure ligule height on leaves from approximately the middle third of the plant. Ligules on upper, newly emerging leaves are not as well-developed. On lower leaves, ligules may be degraded
Stem density, persistence, and height
Leaf blade color
The large fluffy inflorescences along with the height of the plants may be the first thing that draw your attention to Phragmites. Don’t rely on these characteristics alone to make an ID. Confirm the ID using characteristics of the sheath, stem texture, stem color, and ligule.
Late winter and early summer ID tips