Phragmites communis Trin.. 1972. Biological Flora of the British Isles 128, Journal of Ecology. 60, 585610.
Tribe ARUNDINEAE. A tall reed, with annual cane-like shoots (c. 5 cm-) 2 m (-4 m) high above ground level in Britain, and an extensive perennial rhizome system. Leaf blades flat, c. 3-45 mm wide in Britain (modal maximum leaf width per shoot usually 15-30 mm in British populations), tapering to long slender points, deciduous. Sheaths smooth; auricles prominent. Ligule a fringe of hairs. Panicle often 30 cm, lax, dull purple in Britain (purple to yellow elsewhere); branches smooth, usually with scattered groups of a few long silky hairs. Spikelets 10-15 mm, of (1-) 3-6 florets; rhachilla hairy. Glumes shorter than first floret, lanceolate, upper twice as long as lower. Lemma twice as long as upper glume, linear-lanceolate. Palea shorter, ciliate in upper parts. Florets, except for the lowest, with a basal tuft of long silky hairs, about as long as the lemma. Lodicules 2, oblong. Stamens 1-3 in lowest floret; 3 in others. Ovary glabrous; styles short.
Three species have been recognized (Clayton 1967): Phragmites communis Trin., in temperate regions of both hemispheres; P. karka (Retz.) Trin. ex Steud., in Polynesia, northern Australia, tropical Asia, north-west and west Africa; and P. mauritianus Kunth, in tropical Africa. The two last differ from P. communis sensu stricto in having leaf blades scabrid beneath (at least in the upper half), tips attenuate; rhachilla hairs 4-7 mm, rather sparse; lowest node of panicle often with many branches in a whorl and the branches bare of spikelets for some distance from their base. P. mauritianus, in comparison with P. karka, has a more nearly ovate upper glume, which is shortly acuminate, and shorter (3-5 mm rather than 4-6 mm); the lower often sub-equal; and the lowest lemma broader.
Although Hegi (Fl.1) recognized two subspecies and a number of varieties, Rudescu, Niculescu & Chivu (1965) have shown that a number of important intraspecific characters are the result of phenotypic plasticity and are not genotypic. These include characters often considered to be of taxonomic importance. There are no records of transplant rests between different species of Phragmites.