How to Identify Japanese Knotweed
Learn the key features that set Japanese Knotweed apart — from its leaves and stems to seasonal growth changes.
What to Look For
Japanese Knotweed has distinct characteristics that vary by season. Here’s how to spot it throughout the year:
Spring
- Red or purple asparagus-like shoots emerge from the ground
- Young leaves are rolled up and reddish green
- Stems begin their zig-zag growth pattern
Summer
- Broad, flat, shovel-shaped leaves with pointed tips
- Hollow, bamboo-like stems with purple speckles
- White flower clusters appear around August–September
Autumn
- Leaves turn yellow then brown
- Stems remain standing but begin to dry
- Flowers wilt and drop off
Winter
- Dead, brown stems remain upright and brittle
- No leaves or flowers visible
- Underground rhizomes (roots) remain alive and bright orange inside
Key Features to Confirm
- Leaves: Alternate pattern on the stem, flat base, pointed tip
- Stems: Hollow, jointed nodes, reddish speckling
- Roots: Thick, brittle, orange when snapped
- Flowers: Tiny, creamy-white and in cone-like clusters
Even if you’re not sure, matching just a few features could indicate risk. If in doubt, use our Free ID Tool.