Giant Reed-Grass Family

False bamboo

Arundo donax

Characterisitcs. This European import was introduced to California as an ornamental and for use as a wind-break, as well as for various construction uses. Since its inevitable escape it has become a major problem in natural settings due to its aggressive and dominating growth. In particular it is noxious in areas along river shores, irrigation or ditchbanks, and drainage canals as it grows in tall, solid thickets that may overwhelm large areas. This weed primarily reproduces by rhizomes although seeds are produced. Along with the rhizomes additional thick roots add to the difficulty in attempting physical removal.

Identification.
Giant reed, also known as wild cane, is a tall, perennial grass that can grow to over 20 feet in height. Its fleshy, creeping rootstocks form compact masses from which tough, fibrous roots emerge that penetrate deeply into the soil. Leaves are elongate, 1-2 inches wide and a foot long. The flowers are borne in 2-foot long, dense, plume-like panicles during August and September. 

Giant reed chokes riversides and stream channels, crowds out native plants, interferes with flood control, increases fire potential, and reduces habitat for wildlife, including the Least Bell's vireo, a federally endangered bird. The long, fibrous, interconnecting root mats of giant reed form a framework for debris dams behind bridges, culverts, and other structures that lead to damage. It ignites easily and can create intense fires. 

Giant reed can float miles downstream where root and stem fragments may take root and initiate new infestations. Due to its rapid growth rate and vegetative reproduction, it is able to quickly invade new areas and form pure stands at the expense of other species. Once established, giant reed has the ability to outcompete and completely suppress native vegetation. 

Today, giant reed is widely planted throughout the warmer areas of the United States as an ornamental and in the Southwest, where it is used along ditches for erosion control.

Reproduction of giant reed is primarily vegetative, through rhizomes which root and sprout readily. Little is known about the importance of sexual reproduction in giant reed, or about its seed viability, dormancy, and germination, and seedling establishment. Research on these topics may yield some additional improvements in the management of giant reed. 

Images Courtesy of John M. Randal.

The leaves are arranged alternately with 2 distinct rows along either side and clasp to the stem. On the major stems the leaves can be up to 3 inches wide, with rough, raspy edges. Flower heads are plume-like and up to 2 feet.

Management Options. Areas infested with giant reed are best restored through chemical means. Mechanical control (e.g., repeated mowing) may be somewhat effective, but if small fragments of root are left in the soil, they may lead to reestablishment. 

Chemical
Systemic herbicides, such as glyphosate (e.g., Rodeo®), may be applied clumps of giant reed, after flowering, either as a cut stump treatment or as a foliar spray. When applying herbicides in or around water or wetlands, be sure to use products labeled for that purpose to avoid harm to aquatic organisms. 

Fire
Prescribed burning, either alone or combined with herbicide applications, may be effective if conducted after flowering. Once giant reed has been reduced sufficiently, native plants may be seeded or transplanted at the treated site.