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Japanese Knotweed
Polygonum
cuspidatum
Identification
Japanese knotweed is an herbaceous perennial that resembles a shrub
in form and can grow to 10 feet tall. Leaves are simple, alternately
arranged, and broadly oval to somewhat triangular. The leaves vary
in size according to conditions, but average about six inches at
midrib. Tiny, greenish-white flowers occur in attractive branched
sprays in summer. They are soon followed by tiny winged fruits. In
fall, stems turn a showy red color.
Origin
Eastern Asia
Habitat
Grows well in a variety of conditions, as long as water is
available. It tolerates shade and grows well in low areas and in
riparian areas along streams and rivers.
Ecological Threat
Very fast growth, forms dense stands in moist to wet areas where
native plants are quickly shaded or crowded out. Once planted as an
ornamental, knotweed is now invading riparian areas all over the
country. It has a very shallow root system, and provides very little
protection from erosion on stream banks. Once established, it is
very hard to eradicate or control.
Recommended Native Alternatives
-
Sweet
pepperbush (Clethra alnifolia)
-
Silky dogwood
(Cornus amomum)
-
Rivercane (Arundinaria
gigantea)
These pages are designed to give the
layperson a general overview of non-native invasive plants commonly
found in the upper Hiwassee River watershed. For more comprehensive
and technical information about a particular species, visit one of
the web sites from our
Links
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