Identifying Japanese Knotweed

Identifying Japanese Knotweed in Spring

New growth appears as rapidly growing soft red/purple shoots. The stems are hollow and bamboolike and can grow up to 10cm per day. The leaves grow on alternate sides of the stem producing a zig-zag pattern in the stem.

Identifying Japanese Knotweed in Summer

During the summer months, the Japanese Knotweed will be fully formed with large green leaves. As summer continues, the Japanese Knotweed will begin to flower. The flowers of the Japanese Knotweed are creamy-white clusters.

Identifying Japanese Knotweed in Autumn

In Autumn the dense covering of leaves will remain, however, they start to turn yellow and wilt as we move into September and October. The knotweed plants are still about 2-3 metres tall, and the hollow stems start to turn brown.

Identifying Japanese Knotweed in Winter

In winter, Japanese Knotweed will have lost all of its leaves, but the long clustered shoots will remain. These canes will die off and turn brown and brittle. These winter stems can remain erect through the winter if left undisturbed.

This isn’t the end of the weed, however – its ‘crown’ and rhizome remain dormant throughout the winter, waiting for spring to return so that they can start the cycle again. This is an ideal time to dig out and replace the contaminated ground at a time when the weed is dormant, and the garden or green areas aren’t getting as much use.