Genus: It is a giant, erect perennial herb which forms dense thickets. Stems grow 4-5 m in a single season and bear large, alternate leaves up to 40cm long with heart-shaped bases. In summer plants bear dense panicles of small green-white flowers and seed is sometimes produced. It hybridises with Japanese Knotweed to give a highly invasive hybrid knotweed F. x bohemica.
Details: Giant knotweed has been planted in large gardens and private estates for at least 100 years and has escaped into the wild via throw-outs and river flooding. It is widespread but not abundant across the British Isles and is much less common than Japanese Knotweed.
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