NATIVE RANGE: East Asia (Japan)

FIRTS FINDING IN SLOVENIA: 1970

PATHWAYS: horticulture

POSSIBLE TO FIND:  year round

FLOWERING SEASON: July – September

DESCRIPTION: Herbaceous perennial with strong, extensively spreading rhizomes, forming large clonal colonies. The stem is hollow and jointed. Leaves are up to 40 cm long, thin, slightly rough to the touch, with a cordate base and a few hairs on the veins on the underside. Flowers are small and whitish with five tepals, borne in dense, drooping clusters.

HABITAT: Growing on forest edges and in forest clearings, on ruderal sites (embankments and roadsides).

STATUS: Widespread and common over Europe, with most records from the United Kingdom and Germany. In Slovenia, currently only known from about 20 locations. Of the alien Knotweeds the least spread and also less quickly spreading than the other species. 

SIMILAR SPECIES: Japanese knotweed (F. japonica) and the hybrid between Japanese and giant knotweed – Bohemian knotweed (Fallopia x bohemica) – are both much lower. Japanese knotweed grows up to 2 m, and Bohemian knotweed is only slightly taller. Leaves of Japanese knotweed are up to 12 cm long, slightly longer than broad, with a truncate base. Leaves of Bohemian knotweed are up to 30 cm long and have a slightly cordate base.

SOURCE: Field Guide to Invasive Alien Species in European Forests