Beatrice Vasey
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    Is it Japanese knotweed? Identification checker

    Answer a few questions about what you can see this month, or upload photos of the plant. The checker compares it with Japanese knotweed and the nine plants most often mistaken for it, and tells you plainly when it's probably something else.

    Beatrice Vasey is a horticulturist and botanical surveyor, not a knotweed treatment company.

    When are you looking at the plant?

    Knotweed looks completely different through the year, so the questions change with the season.

    Japanese knotweed through the year

    SeasonWhat you'll see
    SpringReddish-purple shoots push up from pink buds at ground level.
    SummerDense stands of hollow, bamboo-like stems with red speckles, carrying spade-shaped leaves up to 14 cm long in a zig-zag pattern.
    Late summer and autumnClusters of small creamy-white flowers. This is also when herbicide treatment works best.
    WinterThe leaves drop and the stems become dry brown canes. Dug up, the rhizome is orange inside.

    Plants often mistaken for Japanese knotweed

    Plenty of garden plants and weeds get mistaken for knotweed. These are the usual suspects, and the quickest way to tell each one apart.

    PlantWhy it's mistaken for knotweedHow to tell it apart
    Hedge bindweedCalystegia sepiumIts leaves are a similar size and shape, and it smothers fences and hedges in summer.Bindweed twines round other plants with thin stems and has big white trumpet flowers. Knotweed stands up on its own on thick, hollow canes.
    Russian vineFallopia baldschuanicaIt's a close relative, with very similar sprays of small white flowers in late summer.Russian vine is a woody climber that scrambles over fences, sheds and trees. Knotweed doesn't climb.
    Himalayan balsamImpatiens glanduliferaIt grows in tall, dense stands with hollow, reddish stems, often on the same riverbanks.Balsam has long, narrow, toothed leaves in pairs or threes, pink slipper-shaped flowers and juicy stems that snap easily. It dies right back in winter and leaves no standing canes.
    BambooMany species, including Phyllostachys and SasaIts canes are hollow and jointed, like knotweed stems.Bamboo canes are woody and stay green, yellow or black all year, with sprays of narrow, grass-like leaves. Knotweed has broad leaves and dies back to brown canes in winter.
    Broad-leaved dockRumex obtusifoliusIts young leaves and stalks are often red-tinged in spring, like knotweed shoots.Dock grows as a clump of large, long-oval leaves from the ground, with flower spikes that turn rusty brown. It never makes a thicket of canes.
    LilacSyringa vulgarisIt has heart-shaped leaves and can sucker into a dense thicket.Lilac is a woody shrub with leaves in opposite pairs and scented flower clusters in May. Knotweed has one leaf at each joint and no woody stems.
    DogwoodCornus speciesIts red stems can look like knotweed's red shoots in winter and early spring.Dogwood is a woody shrub with leaves in opposite pairs, and its leaf veins curve round towards the tip. Knotweed stems are hollow, not woody.
    Himalayan honeysuckleLeycesteria formosaIts stems are hollow, green and jointed like bamboo.Himalayan honeysuckle has leaves in opposite pairs and drooping chains of white flowers among dark red bracts, then purple-black berries. Knotweed leaves alternate along a zigzag stem.
    Chameleon plantHouttuynia cordataIt has heart-shaped, often red-tinged leaves and spreads by underground stems.Chameleon plant stays low, usually below knee height, and its leaves smell of orange peel when crushed. Knotweed usually grows to about 2 m.

    If you've found knotweed

    • Leave it alone for now. Cutting, strimming or digging spreads fragments of stem and root, and each can grow into a new plant.
    • Note whether it's within 3 m of your boundary or close to the house. Those distances matter to surveyors and mortgage lenders, as our guide to Japanese knotweed treatment explains.
    • Check whether it has been recorded near your postcode, which can show whether it's spreading along a stream, railway or road nearby.
    • Have it confirmed before you pay for treatment. In County Durham, Beatrice can identify it on site.

    Knotweed identification questions

    What does Japanese knotweed look like?

    In summer it forms dense stands up to 3 m tall of hollow, bamboo-like stems speckled with purple, with shield-shaped leaves on alternate sides of a zigzag stem. Sprays of small creamy-white flowers follow from late summer, and in winter the stems die back to hollow brown canes, often still standing.

    When is the easiest time to identify knotweed?

    From late spring to autumn, when it is in full leaf. Spring is also good, because the red asparagus-like shoots are distinctive. Winter is hardest, when only the dead brown canes are left.

    What is most often mistaken for Japanese knotweed?

    Bindweed, Russian vine, Himalayan balsam, bamboo, broad-leaved dock, lilac, dogwood, Himalayan honeysuckle and chameleon plant. The quickest checks are whether the stem is hollow and speckled, and whether the leaves alternate along a zigzag stem.

    Can you identify Japanese knotweed in winter?

    Often, from the dead, hollow brown canes it leaves behind, standing or fallen, but it's easy to get wrong. If you're not sure, look again in April when the red shoots come through, or have it checked.

    Is it illegal to have Japanese knotweed in my garden?

    No. Having it on your land isn't an offence, but letting it spread into the wild is, and in England and Wales a council can act if it harms neighbours. Our guide to knotweed treatment and the law covers what you have to do.

    Is there Japanese knotweed near me?

    Enter your postcode on our Japanese knotweed map to see records within 5 km, from botanists, local records centres and river surveys.

    Sources (18)