Phragmites australis

Lore & Background

Phragmites australis is a helophyte occurring in shallow water in ponds, lakes, rivers, fens, ditches, and similar habitats, and it also tolerates brackish water in estuaries and lagoons. The erect stems grow to 1.5–4 m tall, occasionally to 6 m, with the tallest plants growing in areas with hot summers and fertile growing conditions. Where conditions are suitable it can spread at 5 metres or more per year by horizontal runners, which put down roots at regular intervals. The leaves are glaucous green to greyish-green, fading to buff-brown in autumn before falling to leave the stems standing through the winter. The flowers are produced in late summer in a dense, dark purple panicle, 15–50 cm long, and later the numerous long, narrow, sharp pointed spikelets appear greyer due to the growth of long, silky hairs that help disperse the minute seeds.

Four subspecies are accepted by the Plants of the World Online database: subsp. americanus (North America, widespread except for southeastern United States), subsp. australis (Europe, Asia, Africa, Australia, widespread except for tropical Africa and tropical southeast Asia), subsp. berlandieri (southern United States to Central America, northern, western and southern South America), and subsp. isiacus (northern half of Africa, Mediterranean region, southwest to central Asia, and disjunct eastern Asia). Subsp. australis is additionally introduced and invasive in North America, where it outcompetes the native subsp. americanus, and also in New Zealand and locally in Brazil. Morphological distinctions between subspecies australis and americanus include shorter ligules of up to 0.9 mm in subsp. australis as opposed to over 1 mm in subsp. americanus, and shorter glumes mostly under 3.2 mm against mostly over 3.2 mm.

Common reed is of immense importance in wildlife conservation, a keystone species creating a unique habitat on which numerous other species depend. Reedbeds of over 25 hectares are particularly important for some larger species such as Eurasian bittern, western marsh harrier, and great reed warbler; the huge 1,700 km² Danube Delta reedbeds are one of the most important wildlife sites in the whole of Europe. Common reed is suppressed where it is grazed intensively by livestock, reduced to small shoots within the grassland sward, or disappearing altogether. Limited regulated grazing is however beneficial, as it opens up denser stands and allows for the rejuvenation of the reeds and also a more diverse flora and fauna.

Reader's Guide

Phragmites australis is notable for its dual role as both a keystone species in native habitats and a problematic invasive in regions where the European subspecies has been introduced. In North America, the status of Phragmites australis was a source of confusion and debate; it was commonly considered a non-native and often invasive species, introduced from Europe in the 1800s, but there is evidence of its existence as a native plant long before European colonisation. The North American subspecies, P. a. subsp. americanus, is markedly less vigorous than the European subspecies. The expansion of Phragmites in North America is due to the more vigorous, but similar-looking, European subsp. australis, which outcompetes native vegetation and lowers local plant biodiversity. It forms dense thickets unsuitable for native fauna, displaces plants such as wild rice, Typha, and native orchids, and its high above-ground biomass blocks light to other plants, allowing areas to turn into monoculture quickly. Decomposing Phragmites increases marsh accretion more rapidly than native marsh vegetation. Gallic acid released by phragmites is degraded by ultraviolet light to produce mesoxalic acid, harming susceptible plants and seedlings. Control is difficult; one of the most effective methods is burning over 2–3 seasons, and ongoing research suggests goats could be effectively used. Since 2017, over 80% of the beds of Phragmites in the Pass a Loutre Wildlife Management Area have been damaged by the invasive roseau cane scale (Nipponaclerda biwakoensis), threatening wildlife habitat. In Louisiana, the reed beds are considered critical to the stability of shorelines of wetland areas and waterways of the Mississippi River Delta, and the die-off is believed to accelerate coastal erosion. Common reed is the primary source of thatch for traditional roof thatching in Europe and beyond, and is extensively used in phytoremediation, as the root hairs are excellent at filtering impurities in waste water. It also shows excellent potential as a source of biomass, and stems can be made into eco-friendly drinking straws. Many parts of the plant can be eaten: young shoots raw or cooked, hardened sap from damaged stems fresh or toasted, stems dried and toasted like marshmallows, seeds crushed and cooked into gruel, and roots prepared similar to cattails.