Question

Which plant is described by these clues? Each flower has no petals whatever, only a pair of dry chaffy scales around it, and every fertile one ripens into a single one-seeded {caryopsis}. The genus name is Greek for a hedge or a screen, from the old practice of cutting the stems to weave windbreaks and fences along ditches. Stems are hollow and round in cross-section, interrupted by hard swollen joints, and every leaf rises from one of those joints inside a {sheath} split down one side. The long white silky hairs that make the ripe plume look feathery grow from the slender axis between the {florets}, leaving the back of each floret's own outer scale smooth. Where each blade meets its sheath sits a short {ligule} of hairs 0.04 to 0.08 inch (1 to 2 mm) long instead of the thin dry membrane most of its relatives carry there. Its species epithet means nothing more than 'southern', an odd label for a plant that now grows on every continent except Antarctica. It floods brackish estuary margins, tidal marshes and roadside ditches with dense single-clone thickets, travelling on {rhizomes} that push more than 6 feet (1.8 m) deep and lengthen by up to 6 feet (1.8 m) a year. Canes 6 to 15 feet (1.8 to 4.5 m) tall stand dead and upright right through winter, their tawny plumes still rattling above the ice the following spring. A single plume can shed thousands of seeds, yet nearly every new thicket in North America begins instead from a snapped cane or a broken piece of {rhizome}. Thatchers in eastern England cut whole marshes of its winter stems for roofing, and engineers plant beds of it to scrub sewage in constructed wetlands.

Accepted Answer

Phragmites australis

Name That Plant #072