Native to warmer areas of Europe, and introduced to California as an ornamental and wind-break planting, as well as for use as a roofing material, mats or screens. It easily escapes cultivation and 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. It grows in tall, solid thickets that may overwhelm large areas.
While seeds are produced, reproduction is primarily from rhizomes. These are well branched and are thick, knotty, woody, and extremely tough. Along with the rhizomes additional thick roots add to the difficulty in attempting physical removal.
Mature plants can grow as high as 20 feet, with hollow stems strongly resembling bamboo. The newer stems are up to 1 inch in diameter, and begin as a bright green but mature to yellowish and eventually brown along the lower ends. Leaves are alternate and in two distinct rows along either side of the stem. On the major stems the leaves can be up to 3 inches wide, with rough, raspy edges. Where the leaf base clasps the stem is has distinct wavy ripples in it.
Flower heads are plume-like and up to 2 feet long, with many dozens of spikelets along it that may be up to 6 inches long themselves, tapering shorter toward the end.
Characteristicts Important to Control:
Physical removal is extremely difficult due to the strength of the plants stems and rhizomes and the extensive underground system of these rhizomes and roots. Re-growth can occur from small pieces of rhizomes that may remain.