Himalayan knotweed (Persicaria wallichii)

A knotweed native to the Himalayas, now a garden escape mainly in the west of Britain and invasive in Ireland. It is mainly found in moist situations including river banks. Himalayan knotweed looks like Japanese knotweed but is smaller and its leaves are long and thin.

This definition is abridged from A – Z of tree terms: A companion to British arboriculture.
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