Summer Identification semi-dense stand, with lush green
June to September. Japanese 20cm long. In late summer, it flowers,
knotweed canes will grow to around
2-3 metres high. The plant has free
standing upright stems (which
heart or shovel-shaped leaves, up to
producing panicles of small creamy-
white flowers.
resembles bamboo) and forms as a
Autumn Identification
October to December. The flowers have
died and just like other herbaceous
perennial plants, Japanese knotweed
goes into senescence as the above
ground parts of the die off for winter.
Leaves turn yellow and start to fall in
the autumn.
Winter Identification
The underground crown and rhizome
of the plant remains live but in a
dormant state over winter. It will
produce new growth again in the
spring. The above ground canes die
off and turn brown and brittle. The
alternate (non-symmetrical) stem
growth pattern (zig-zag) can still be
seen for identification.
Issue 38 2019 Landscape & Urban Design
37