NATIVE RANGE: Central and East Asia (China, India, Afghanistan)

FIRST FINDING IN SLOVENIA: not yet found in Slovenia

PATHWAYS: horticulture

POSSIBLE TO FIND: year round

FLOWERING SEASON: July – September

DESCRIPTION: A fast-growing perennial with an erect, hollow stem that is green, with twigs that zig-zag from one leaf node to the next. Reddish-brown leaf sheaths envelop the stem nodes at the base of each leaf. Leaves are spiralling, lanceolate, with an acuminate apex, truncate at the base, with two small lobes. Leaf stalks and at least the lower part of the mid-vein are reddish. Flowers are small, white to pink, clustered in upright, branched spikes at the end of branches and in the axils of the upper leaves. Fruits are small brown achenes but rarely form.

HABITAT: Forests, shrubland and bare slopes.

STATUS: Invasive in northern Europe and appears to be established in Central Europe. In Slovenia not yet found in nature. 

SIMILAR SPECIES: Japanese knotweed (Fallopia japonica) and hybrid Bohemian knotweed (Fallopia x bohemica) have broadly ovate leaves. In both taxa, clusters of flowers are also formed in the middle of branches, not only in the upper part. Prince’s feather (Polygonum orientale) has bright pink flowers. European natives redshank (P. persicaria), water-pepper (P. hydropiper) and tasteless water-pepper (P. mite) have much smaller leaves and unbranched white or pink flower spikes.

SOURCE: Field Guide to Invasive Alien Species in European Forests