Giant reed is a perennial clump-forming grass that can attain heights
of 7-8 meters. The leaves are chiefly cauline, long tapering to a sharply
acute tip. The blades are flat 2-6 cm wide with scabrous margins. The
ligule is membranous and minutely ciliate. The panicles are large and
plumy and may reach a length of 30-70 cm. Long hairs on the lemmas give
the plumes a feathery appearance.
Giant reed grows rapidly and can readily propagate from rhizomes, thereby
forming tall dense stands. Fertile caryopsis seldom develop. The grass
commonly invades areas along streambeds.
Giant reed easily displaces native species and forms monospecific stands
along waterways. These monocultures consume more water than native plants,
create flood-control problems, and the large biomass that dies back each
season creates a fire hazard.