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Invasive Species Sheet - Japanese Stilt Grass

Invasive Species Identification Sheet

Japanese Silt Grass (Polygonum cuspidatum Sieb. & Zucc.)

Alternate Common Names: Vietnamese Stilt Grass; Asian Stilt Grass; Nepalese Browntop; Chinese Packing Grass; Annual Jewgrass; Basketgrass; Mary’s Grass

Alternate Latin Names: Andropogon vimineus Trin.; Microstegium imberbis Nees ex Steud.; M. willdenovianum Nees ex Lindl.; Eulalia viminea (Trin.) Kuntze; Pollinia viminea (Trin.) Merr.; P. imberbis Nees ex Steud.; P. willdenoviana (Nees ex Lindl.) Benth.
- annual grass; shade tolerant; lush, dense, light green stands are prominent in late summer
- sprawling growth; frequently with nodes marked by stiff, root-like structures dropping into the ground and leafy stems growing upward
  as tall as 3'; easy to pull up
- leaves alternate, 1 1/4"–3" long, up to 3/8" wide, not thick; with pointed tip and tapered base
- leaf midvein area frequently is wide and shiny white (best seen in sunlight)
- flowers mid-Sept. on stalks attached at ends of leaf stems; seeds late-Sept. or early Oct.

Japanese Stilt Grass is generally recognizable by vegetative characteristics. It is often confused with (and may grow
intermixed with) the native White Grass (Leersia virginica Willd.). Important characteristics to check for on
Japanese Stilt Grass vs. White Grass are: (1) stem nodes hairless (check with hand lens) vs. tiny hairs protrude
from nodes (usually visible even without a hand lens), (2) all thin roots vs. some roots are short, thickened
rhizomes (underground stems), (3) flower clusters on 1 or 2 (up to 5) densely-packed, spike-like branches each
with many pairs of green spikelets vs. flowers in an open panicle usually with 5+ branches, (4) late fall leaf color is
wine red/purple and pale yellow vs. pale green or tan.

In New England, Japanese Stilt Grass seeds sprout in June. Plants grow rapidly on shady, moist sites where the soil
has been disturbed, for example, riparian areas scoured by high water, roadsides, and lawns.