Japanese knotweed - Polygonum cuspidatum
Origin: Eastern Asia
Background Japanese knotweed, a member of the buckwheat family, was
introduced into the U.S. as an ornamental on estates in the 1870s. It has
also been used as an erosion control plant. The plant, which can grow as
tall as 15 feet, has bamboo-like stems and is sometimes called Japanese
bamboo. As with many invasive plants, knotweed thrives in disturbed areas
and once established can spread rapidly, creating monoculture stands that
threaten native plant communities. Japanese knotweed can tolerate deep
shade, high temperatures, high soil salinity and drought. It is commonly
found along streams and rivers, in low-lying areas, disturbed areas such as
rights-of-way, and around old home and farm steads.
Identification
Plant: upright, shrubby, herbaceous perennial Height: 10 to 15 feet in
height Stems: smooth, stout, swollen where the leaf meets the stem.
Membranous sheath surrounds joints of the stem Leaves: normally about 6
inches long by 3 to 4 inches wide, alternating on stem, broadly oval to
somewhat triangular or heart-shaped, pointed at the tip Flowers & fruits:
small greenish-white flowers in branched sprays in summer, followed by small
winged fruits Seeds: triangular, shiny, very small, about 1/10 inch long
Spreads primarily by seed, stem fragments, and by vegetative means with
long, stout rhizomes. Seeds can be transported by water, wind, on people's
shoes, by animals, and as a contaminant in soil.
Japanese knotweed spreads rapidly, forming dense thickets that
crowd and shade out native vegetation, reducing species diversity and
negatively impacting wildlife habitat. Once established, populations of
Japanese knotweed are extremely persistent and hard to eradicate.
Prevention and Control
Single young plants can be pulled by hand
depending on soil conditions and root development. Re-sprouting can occur if
all of the root system and runners aren't removed. Chemical controls include
application of glyphosate and triclopyr herbicides to freshly cut stems or
to foliage.
Links
USDA NRCS PLANTS Database
http://plants.usda.gov/java/profile?symbol=POCU6
Invasive Plants Council of NYS
http://www.ipcnys.org/sections/target/japanese_knotweed_overview.htm
Invasives.org
http://www.invasive.org/eastern/biocontrol/12Knotweed.html