Lookalike guide
Japanese knotweed vs Lilac
Young lilac suckers have similar heart-shaped leaves, which is why lilac is one of the most common knotweed false alarms.
Lilac (Syringa vulgaris): Garden shrub — harmless.
| Feature | Japanese knotweed | Lilac |
|---|---|---|
| Stems | Hollow canes that die back every winter | Solid, woody grey-brown branches that stay all year |
| Leaf arrangement | One leaf per joint, alternating up the stem | Leaves in opposite pairs |
| Flowers | Cream sprays in August–October | Scented purple or white cones in May |
Quick test
Look at the leaf joints: opposite pairs means lilac; one leaf per joint on a zigzag means knotweed.