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Telling Japanese knotweed from other plants

How it changes through the year, and the common Widnes garden plants it gets confused with.

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Red Japanese knotweed shoots in spring
Spring: red shoots
Japanese knotweed in summer leaf
Summer: full leaf
Surveyor checking a knotweed stand
Not sure? Send a photo

In spring

From April, purple-red spears with curled leaves break the ground and can add several centimetres in a single day.

In summer

By midsummer it stands two or three metres tall. Stems are hollow and speckled with purple, they zig-zag at each joint, and the leaves are broad with a flat base.

In autumn

Cream flower sprays open late in the season. After that the leaves yellow and drop.

In winter

Dead canes remain upright, brown and brittle. Below ground the rhizome is still alive.

Plants it gets confused with

Bindweed climbs and twists round other plants. Dogwood has woody stems and leaf veins that curve. Himalayan balsam has pink flowers and likes damp ground. If in doubt, send a photo.

The short answers

In brief

What does Japanese knotweed look like?
Hollow, bamboo-like stems with purple or red speckles, growing in a zig-zag from node to node. Leaves are shield or heart-shaped with a flat base, up to about 14cm long. Plants reach 2 to 3 metres in summer.
What does knotweed look like in spring?
Red or purple asparagus-like shoots with rolled-back leaves appear from April. They can grow several centimetres a day.
What does knotweed look like in winter?
The leaves drop and the canes die back to brown, hollow, brittle stems that often stay standing through winter. The rhizome underground is still alive.
What is commonly mistaken for Japanese knotweed?
Bindweed, Russian vine, dogwood, lilac, houttuynia and Himalayan balsam are frequent look-alikes. Bindweed twines around other plants; knotweed stands on its own stems.
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What happens next

Knotweed surveyAn on-site visit to confirm the plant and record the stand.Free knotweed ID from a photoMessage us a picture and we say what the plant is, at no cost.Knotweed plan for mortgages and salesThe management plan a lender or buyer will ask for.Knotweed from a neighbourA dated record of where it is and where it is heading.Knotweed spraying programmeHerbicide treatment over several seasons, with return visits.Knotweed excavationDigging out the stand and its rhizome in a few days.Knotweed root barrierUpright membrane that stops rhizome crossing a line.Knotweed on building plotsSurveys and removal for Widnes development land.Knotweed for landlordsSurveys and treatment for rented houses and flats.
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