Giant Reed (Arundo donax) is a tall perennial grass native to Asia and widespread throughout the Mediterranean region, where for millennia it has been cultivated for use as a building material, erosion control, windbreak, and now as a biofuel crop. Giant Reed was introduced into California in the 1820s for erosion control, and has been widely planted throughout the warmer states as an ornamental and for erosion control along drainage canals. It has since escaped and become a major invasive weed throughout the South, from California east through Texas and the Gulf Coast, and north along the Mississippi and Ohio River drainages as far north as Missouri and Kentucky, and in east coastal states to Virginia. Once established, Giant Reed forms dense monoculture stands, altering the community by displacing native species. This invasive plant will interfere with drainage and lead to flooding and erosion issues. Dead and dry stands (and accumulation of fuel) pose a fire hazard.
Giant Reed is a very large clumping grass with hollow stems ¼ to 2 inches thick and has a cane-like appearance similar to bamboo. Mature stands are typically 12 to 16 feet in height, but can reach 20 feet. Once established, it tends to form large, continuous, clonal root masses, sometimes covering several acres. Leaves are smooth and alternate on the stem, about 2 inches wide and from 24 to 36 inches long, with rounded bases but tapering to a long point. Leaf bases have persistent hairy tufts. The leaves and stems are typically blue-green but leaves can be variegated to nearly white.
Giant Reed has thick, knotty rhizomes and deep fibrous tap roots, with root mats up to 3 feet thick. The inflorescence is an erect feathery spike 1 to 2 feet long, white to brown, but producing few viable seed. Rather than seed production, it spreads primarily via fragmentation, and fragments as small as 1 inch are viable. In North Carolina, Giant Reed has been reported from 29 counties (as of 2019), ranging from the Mountains (few) to the Piedmont and Coastal Plain (many), usually found in riparian areas and roadside ditches. However, landowners continue to plant named varieties of Giant Reed as an ornamental. There is also great concern over the use of Giant Reed as a biofuel crop in the NC Coastal Plain.
Fact Sheet: Giant Reed