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SEASONAL IDENTIFICATION
JAPANESE KNOTWEED (Fallopia japonica var. japonica)
SPRING
EARLY
SUMMER
FALL
LATE
SPRING
-
LATE
SUMMER
SUMMER
FALL
-
WINTER
Pink and green sprouts emerge and look similar to
asparagus, but are much thicker. Stems are hollow.
Large colonies form by spreading roots called rhizomes.
Japanese knotweed shades out most other vegetation.
Japanese knotweed leaves briefly turn yellow before turning
rust brown in fall. Colonies stand out when plants are rust
colored. Seeds have formed at this time but are not easily
seen until leaf drop.
Bamboo-like main stems are smooth, hollow, and
chambered. Leaf stems are reddish purple and strongly
zigzagged. Oval to heart-shaped leaves have tapered
points.
White flower spikes emerge where the leaf meets the stem.
Flower spikes are seen in loose clusters with many small
white flowers; each of which has five petals. By fall, one
seed per flower has formed on the same spikes.
In winter, stems remain as standing canes. Many plants
have rust-colored seeds but some have already dropped
all seeds. Papery capsules with three wings surround each
oval-shaped seed.
