Common reed commonly forms extensive stands (known as reed beds), which may be as much as a square kilometre or more in extent. Where conditions are suitable it can spread at 5 m or more per year by horizontal runners, which put down roots at regular intervals. It can grow in damp ground, in standing water (up to a metre or so deep), or even as a floating mat. The erect stems grow to 2–6 m tall, with the tallest plants growing in areas with hot summers and fertile growing conditions.
Common reed requires neutral or alkaline water conditions, and so it does not usually occur where the water is acidic. It tolerates brackish water, and so is often found at the upper edges of estuaries and on other wetlands (such as grazing marsh) which are occasionally inundated by the sea.
Common reed is suppressed where it is grazed regularly by livestock. Under these conditions it either grows as small shoots within the grassland sward, or it disappears altogether.
The generally accepted botanical name of common reed is Phragmites australis (Cav.) Trin. ex Steud.. However, it is still often known as Phragmites communis Trin.; other synonyms include Arundo phragmites L. (the basionym), Phragmites altissimus, P. berlandieri, P. dioicus, P. maximus, P. vulgaris.
Recent studies have characterised morphological variation among the introduced and native stands of Phragmites in North America. The Eurasian genotype can be distinguished from the North American genotype by its shorter ligules (up to 0.9 mm vs. over 1.0 mm), shorter glumes (under 3.2 mm vs. over 3.2 mm, although there is some overlap in this character), and culm characteristics. Recently, the North American genotype has been described as a distinct subspecies, Phragmites australis subsp. americanus Saltonstall, Peterson, and Soreng; the Eurasian genotype is referred to as Phragmites australis subsp. australis. Rhizomes of the plant are rich in N,N-DMT alkaloids (Wassel et al. 1985).
Waste water from bathrooms, lavatories and kitchens is routed to an underground septic tank-like compartment where the solid waste is allowed to settle out. The water then trickles through a constructed wetland or artificial reed bed (not to be confused with the natural reed bed habitat), where bacterial action on the surface of roots and leaf litter removes some of the nutrients. The water is then suitable for irrigation or discharge to watercourses.
Some other uses for reeds in various cultures include baskets, mats, pen tips, and a crude form of paper.
One reference to reeds in European literature is Frenchman Blaise Pascal's saying that Man is but a 'thinking reed' (roseau pensant). In La Fontaine's famous fable (The Oak and the Reed, Le chêne et le roseau), the reed tells the proud oak: "I bend, and break not" ("Je plie, et ne romps pas"), before the tree's fall.
Moses was "drawn out of the water where his mother had placed him in a reed basket to save him from the death that had been decreed by the Pharaoh against the firstborn of all of the children of Israel in Egypt" (Exodus 2:10).. However, the plant concerned may have been another reed-like plant, such as papyrus, which is still used for making boats.