Native or Not
Although phragmites is best known as a wetland invader, not all phragmites is bad. Two subspecies are recognized in Michigan; Phragmites australis subsp. australis, sometimes known as Haplotype M, was introduced to the east coast by the early 1800s and has been gradually expanding its range westward. It forms dense monocultures and is capable of dominating wetlands within a few years.
The native subspecies, Phragmites australis subsp. americanus, in contrast, occurs as scattered plants within broader plant communities. It is a component of several wetland communities including Great Lakes marsh, coastal fen and sedge meadows, and is often found along the shores of rivers and lakes.
Differences are most obvious when the two subspecies are side by side; leaf color is subtly different and the bright red stems of the native are distinctive. Generally the non-native form emerges earlier in the season and continues to grow later in the fall. It is considerably more robust and grows in dense colonies.
While it is just beginning to invade and is still relatively sparse, the non-native subspecies may be mistaken for the native. Similarly, in areas with nutrient enrichment, the native form may grow taller and more densely. With practice, the two subspecies can be distinguished. Recently, hybrids have been reported in the literature but they appear to be relatively uncommon.
Click here to download the brochure “Phragmites —Native or Not? Distinguishing native phragmites from the invasive non-native subspecies in the Great Lakes region.”
Scroll down for additional information and photos or click on the links in the table below to jump to specific traits.
|Stem color||dull tan||shiny reddish|
|Leaf persistence||persists||fall off easily|
|Leaf color||bluish green||green|
|Ligule length||0.1-0.4 mm||0.4-1.0 mm|
|Lower glume length||2.6-4.2 mm||4-7 mm|
|Density||dense stands||scattered stems|
|Habit - young non-native||scattered stems||scattered stems (no seedheads) (with seedheads)|
Leaf sheaths of non-native phragmites cling tightly, covering dull tan stems with tiny ridges. The lower leaf sheaths of native phragmites fall off easily, exposing the stem below, which turns red in the sunlight.
The non-native subspecies has stolons (spreading horizontal stems) that can grow up to 50 ft or more in a season. Unlike the upright stems, they can be quite red.
Leaves of the invasive non-native subspecies are a bluish gray-green, while those of the native phragmites are a yellowish green. This is easiest to see when they grow side-by-side.
The ligule is a membranous extension of the leaf sheath at the point where it meets the blade. This membrane may or may not be pigmented; the width of the membrane, not including the fringe of hairs, is the critical measure.
Non-native phragmites has a narrow ligule that ranges from 0.1-0.4 mm, while the native has a wider ligule, ranging from 0.4-1 mm. Because the native phragmites is less sturdy in general, its ligule is more likely to shred and fray by midsummer.
Lower Glume Length
Phragmites seedheads have many branches. Each branch has a number of spikelets, and each spikelet includes a number of florets. At the base of each spikelet are two bracts, called glumes.
Non-native phragmites' lower, shorter glume is usually 2.6-4.2 mm long while that of the native subspecies is longer at 4-7 mm.
Density and Size
Invasive non-native phragmites forms dense monocultures, rapidly outcompeting native species. Its stems break down very slowly, forming a dense thatch. As seen in the upper photo on the near right, it blocks all light, excluding native vegetation. It can reach up to 6 m (20 ft) in height, often blocking shoreline views.
The native species is less robust. Typically it reaches 2 m (6.5 ft) in height and grows as scattered stems. It may grow taller and form dense colonies in response to nutrient enrichment, but the stems break down quickly and other species have enough light and space to grow beneath it, as seen in the upper photo on the far right.
In the photo below, the non-native form is taller the native, with larger seedheads. The density of the native suggests nutrient enrichment on the site.
Like many invasive species, non-native phragmites begins growing earlier in the season and continues later in the fall than its native counterpart. In the photo on the right (shared with density and size account), the invasive phragmites is just beginning to senesce and still retains much of its color. The native, in contrast, is already dormant.
Photos of the two seedheads below were taken on the same day; the non-native is just beginning to expand, while the native is fully expanded.
Habit - Young Non-Native (Catching it Early!)
At first glance, new invasions can resemble mature populations of the native species. This is particularly true when thatch has not yet begun to accumulate, and stems are shorter and widely spaced.
The stems of the young infestation below on the left are widely spaced like the mature native population on the right. However, they lack the seed heads present on most of the native stems. The red stems of the native are distinctive, also.
Early recognition is critical. Phragmites stores energy underground in its extensive network of rhizomes; the older it is, the harder it is to control. Recognizing the non-native form of phragmites early in its invasion increases the opportunity for successful eradication dramatically.
- Are the stems dull tan or red and shiny?
- Are the leaves green or blue-green?
- Do the stems persist over several years or break down quickly?
- Is this a new or mature population-do most stems have seedheads?
- How wide are the ligules? Glume length?