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How to tell Japanese knotweed from other plants

What it does through the year, and the Bolton garden plants that get confused with it.

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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

Spring

From April, red-purple spears with tightly furled leaves force their way up and can grow several centimetres in a single day.

Summer

By July it stands two to three metres tall. Stems are hollow and speckled purple, with a kink at every joint, and the leaves are broad and shield-shaped with a flat base.

Autumn

Sprays of creamy flowers appear late in the season. Not long after, the leaves yellow and drop.

Winter

The dead canes stay upright, brown and brittle. Below the surface, the rhizome is alive and waiting for warmer weather.

Plants it gets mistaken for

Bindweed winds round whatever it meets. Dogwood has woody stems and curved leaf veins. Russian vine is a climber with lacy flowers. Himalayan balsam has pink blooms and likes damp ground, such as the banks of the Croal and Irwell. When 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.
Found it?

What happens next

Knotweed surveyWe visit, confirm the plant and plot the stand.Free knotweed ID from a photoSend a picture. We name the plant at no cost.Knotweed plan for mortgages and salesThe management plan that lenders and buyers ask for.Knotweed from next doorA dated record of where it sits and where it is heading.Knotweed spraying programmeHerbicide treatment across several seasons, with return visits.Knotweed excavationDigging out the stand and rhizome within days.Knotweed root barrierUpright membrane to stop roots crossing a line.Knotweed on building plotsSurveys and removal for Bolton development land.Knotweed for landlordsSurveys and treatment for rented houses and flats.
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