Japanese knotweed (complex)
cuspidatum, sachlinese & polystachyum])
Stem/Leaves: The stems can
grow up to 10 ft. tall. The leaves are broadly oval to
somewhat triangular with a texture similar to satin. The stems
are usually angled at each node. (2)
Flower: The flowers are
small and can be a creamy white to to a green/white. They
grow in a plum like patterns in branched clusters from leaf
axles near the end of the stems. (2)
Probable Entry: It was
introduced to many areas, including Montana, as an
ornamental. Part of the reason it spreads so quickly is
due to the fact that it was very popular as an ornamental for a
Seeds: It has tiny seeds
which are hidden inside husks embedded in paper like sheaths.
Spread: This plant
spreads by long rhizomes (under ground stems) that can survive
the toughest of conditions, as well as spreading through plant
cuttings and seeds. (1)
Infestation: This plant
can grow almost anywhere in Montana. It can tolerate tough
conditions such as high temperatures, high salinity, drought,
and floods. (3)
There are currently no legal biological agents in the U.S. Some
are under consideration especially in the U.K. (2)
Grazing and cutting will help to control the knotweed, but will
not totally eradicate it. (2)
Chemical Control: This
is the most effect form of control. Japanese knotweed will
often need repeated treatments before dying completely.
Some effective herbicides are glyphosate and 2, 4-D amine. (2)
1. CABI Bioscience and the
Japanese Knotweed Alliance.
"Japanese Knotweed". Japanese Knotweed Alliance. 2007.
CABI. February 16, 2008.
2. Remaley, Tom. "Least Wanted". Japanese
Knotweed. May 16, 2007. Plant
Conservation Alliance. February 17, 2008.
3. No author. "Invasive Species". Japanese Knotweed.
15, 2007. Invasive.org.
By: Helen H. and Marina
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