ORIGIN: Vzhodna Azija (Japan)

FIRST FINDING IN SLOVENIA: 1900

PATHWAYS: horticulture

POSSIBLE TO FIND: March – November (in winter it is possible to find dry stems)

FLOWERING SEASON: July – September

DESCRIPTION: Herbaceous perennial with strong, extensively spreading rhizomes, forming large clonal colonies. The stems are hollow and jointed, up to 2 m tall. Leaves are up to 12 cm long, thin, slightly rough to the touch, slightly longer than broad, with a truncate base.. Flowers are small and whitish with five tepals, borne in dense, upright clusters.

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

STATUS: Widespread and common. 

SIMILAR SPECIES: Giant knotweed (Fallopia sachalinensis), is taller (mostly over 2 m, and up to 4 m) đ and has larger up to 4o cm long leaves awith a truncate base. Common is also a hybrid between Japanese and Giant knotweed, Bohemian knotweed  (Fallopia x bohemica), which has intermediate characteristics. 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

Frajman B., 2008. Japonski dresnik Fallopia japonica, Informativni list 1, Spletna stran
https://www.tujerodne-vrste.info/wp-content/uploads/2018/05/INF1-japonski-dresnik.pdf, Projekt Thuja. Datum dostopa: 11/05/2018.