Identification: Introduced Phragmites australis subsp. australis is a perennial reed that grows from elongated rhizomes or stolons; 1-6 meters tall, forms dense stands which include both live and standing dead stems from previous year’s growth (Clayton et al. 2006, Klein 2011).
Leaves and Stems:
Culms (stems) erect; hollow; reed-like; simple; 150–600 cm long; 5-15 mm thick; hollow internodes (Clayton et al. 2006, Klein 2011). Culms are tan in color; ridged or ribbed; have a rougher texture than the native common reed (Swearingen and Saltonstall 2010).
Leaves are linear to lanceolate-linear; flat; drooping; leaf-blades deciduous at the ligule; 20–60 cm long; 8–32 mm wide with pointed tips (Clayton et al. 2006, Klein 2011). Leaf blade surface smooth; cauline (Clayton et al. 2006). Leaves are blue green and usually darker than the native lineage (Swearingen and Saltonstall 2010). Each leaf consists of a blade and a loose sheath separated ciliate ligules that form minute membranous rims fringed with hairs; 0.2-0.6 mm long (Clayton et al. 2006, Klein 2011). Leaf sheaths adhere tightly to culm throughout the growing season; persistent (Swearingen and Saltonstall 2010). Leaf-blade apex attenuates; filiform (Clayton et al. 2006).
Flower-head and Flowers:
Inflorescence a panicle; bearing juvenile spikelets at emergence (Clayton et al. 2006). Panicles are oblong, purplish when young, straw colored at maturity; 15-50 cm long; 6-20 cm wide (Clayton et al. 2006, Klein 2011). Primary panicle branches divided; bearing spikelets almost to the base Clayton et al. 2006). Spikelets solitary; pedicelled (Clayton et al. 2006). Pedicels are filiform (Clayton et al. 2006). Spikelets comprising 3–11 florets; with diminished florets at the apex (Clayton et al 2006, Klein 2011). Spikelets cuneate; laterally compressed; 10–18 mm long; stalked with 6-10 mm long hairs on the stalks; breaking up at maturity (Clayton et al. 2006). Floret callus elongated; 1–1.25 mm long; bearded; obtuse. Glumes are paired; persistent; shorter than spikelets; gaping (Clayton et al. 2006). Lower glume lanceolate; 3–7 mm long; 0.5–0.6 length of upper glume; membranous; without keels; 3–5 veined. Lower glume apex acute. Upper glume lanceolate; 5–10 mm long; without keels; 3–5 veined (Clayton et al. 2006, Klein 2011). Upper glume apex acute (Clayton et al. 2006). Basal florets are sterile florets are male with palea; persist on panicle (Clayton et al. 2006). Lemma are glabrous; lanceolate; 8–15 mm long; membranous; acuminate; with somewhat in-rolled margins. Lower lemmas are unawned and upper lemmas are awned; Lemma apex acuminate (Clayton et al, 2006, Klein 2011). Palea present; with scaberulous keels (Clayton et al. 2006). Flowers typically occur in August and September and form bushy panicles that are usually purple or golden in color with 2 lodicules, 3 anthers, and a glabrous ovary (Clayton et al. 2006, Klein 2011).
Fruit is a caryopsis with an adherent pericarp (Clayton et al. 2006). Seeds are 2 to 3 mm long (Klein 2011). As seeds mature, the panicles begin to look “fluffy” due to the hairs in the spikelet on the rachilla, and they take on a grey sheen (Saltonstall 2005).
Below ground, Phragmites australis forms a dense network of roots and rhizomes which can go down up to two meters in depth to reach deep ground water (MA DCR 2002). The plant spreads horizontally by sending out underground rhizomes and over ground runners which can grow 10 or more feet in a single growing season if conditions are optimal (Swearingen and Saltonstall 2010).
Distinguishing Between Native and Non-native Phragmites australis:
Many morphological characteristics can be used to distinguish native Phragmites australis subsp. americanus from the introduced lineage Phragmites australis subsp. australis. However, there are many overlaps in characteristics making it necessary to look at multiple factors when making a determination based on morphology. The following characteristics should NOT be used to distinguish populations in southern areas (California to the Gulf of Mexico) where the Gulf coast type may be present as it is very similar in appearance to the introduced lineage (Swearingen and Saltonstall 2010).
Introduced Phragmites australis subsp. australis typically forms denser stands than the native Phragmites australis subsp. americanus, the introduced subspecies stands are also more likely to include dead stems from the previous year’s growth (MNFI 2016, Swearingen and Saltonstall 2010). Introduced Phragmites is more likely to form monocultures, outcompeting and excluding other plant species. The native Phragmites, is much less robust, typically occurring in low density stands, and is frequently found with other native plants but it can occasionally occur in very dense stands more typical of the introduced form when enriched with nutrients (MNFI 2016, Swearingen and Saltonstall 2010).
Leaves of the invasive subspecies are a bluish gray-green, while those of the native lineage are typically a lighter yellow-green (MNFI 2016, Swearingen and Saltonstall 2010). This is easiest to see when they grow side-by-side (MNFI 2016).
The leaf sheaths of the introduced Phragmites adhere more tightly to the culm and persist as long as it remains standing, whereas those of the native lineage adhere less tightly and peel back eventually dropping off the culm once the leaf dies particularly at the lower nodes exposing the stem below (MNFI 2016, Swearingen and Saltonstall 2010).
Culms and Rhizomes:
Culms of the introduced lineage are rigid and have a rougher texture than the native, which is usually smooth and shiny (MNFI 2016). Culms of the native lineage are more likely to be red, typically around the nodes and where the leaf sheaths have been lost. Whereas the culms of the non-native lineage are usually a dull tan color (MNFI 2016). However, non-native Phragmites has stolons that can grow up to 50 feet or more in a season and may be red, also a little red may occasionally be seen on the culms of the introduced lineage but it is usually limited to lower nodes, which may lead to confusion (MNFI 2016, Swearingen and Saltonstall 2010). Little black spots are sometimes found on the culms of the native lineage, which are caused by a native fungus that has not yet adapted to the introduced form (Swearingen and Saltonstall 2010). The culms of the introduced form may have a sooty like mildew but it does not have the distinctive black fungal spots (Swearingen and Saltonstall 2010). Rhizomes of the native subspecies rarely exceed 15 mm in diameter and are a darker yellow than the introduced lineage (Swearingen and Saltonstall 2010).
The ligule of the introduced lineage is typically less than 1 mm (0.4-0.9 mm) in length. Ligules of the native are more than 1 mm (1-1.7 mm) (Swearingen and Saltonstall 2010). The native Phragmites is less sturdy and therefore its ligule is more likely to shred and fray by midsummer (MNFI 2016).
For the introduced lineage, the upper glume ranges in size from 4.5-7.5 mm, with most being <6 mm and the lower glume ranges in size from 2.5-5.0 mm, most being <4 mm; the native subspecies has an upper glume ranges in size from 5.5-11.5 mm, with most being >6 mm and lower glume is ranges in size from 3.5-6.5 mm, with most being >4 mm (Swearingen and Saltonstall 2010).
Introduced Phragmites is typically found in ditches, disturbed sites, and can tolerate saline habitats. In the Great Lakes basin, it is frequently found on shorelines (MNFI 2016). The native lineage is usually found in fens, sedge meadow, river banks and shores, and the Great Lake shores (MNFI 2016).
Introduced Phragmites begins growing earlier in the season and continues later in the fall than does the native lineage (MNFI 2016).
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This information is preliminary or provisional and is subject to revision. It is being provided to meet the need for timely best science. The information has not received final approval by the U.S. Geological Survey (USGS) and is provided on the condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from the authorized or unauthorized use of the information.