- Latin synonym: Aconogonum divaricatum, Polygonum divaricatum
- Family: Dock Family – Polygonaceae
- Growing form: Perennial, rhizomatous bushy herb. Forms dense stands.
- Height: 60–120 cm (25–50 in.). Stem glabrous, abundantly branching, curved from joint.
- Flower: Regular (actinomorphic), approx. 3 mm (0.12 in.) wide. White–yellowish tepals 5. Stamens 8. Pistil of 3 fused carpels. Several whorled flowers forming raceme. Inflorescence lax, nodding, axillary, approx. 10 cm (4 in.) long, formed of several racemes. Flowers smell unpleasant.
- Leaves: Alternate. Short-stalked–stalkless leaf blade narrowly elliptic, 5–10 cm (2–4 in.), with entire margins, glabrous (margins can be with short or fringed hairs).
- Fruit: Achene 5–6 mm (0.2–0.24 in.).
- Habitat: Yards, gardens, waste ground. An ornamental and escape.
- Flowering time: June–August.
Genus Koenigia is one of approximately fifty members of the Knotweed family, of which ten grow in Finland. Aproximately 1,200 knotweed species have been identified globally. The most well-known of these in Finland are rhubarb (Rheum rhabarbarum) and buckwheat (Fagopyrum esculentum) and, among wild plants, e.g. common sorrel (Rumex acetosa).
Koenigia divaricata is native to the Far East and is a fairly common ornamental in Finland. This is also true of alpine knotweed (K. alpina) which, although it resembles Koenigia divaricata, has wider, larger and hairier leaves. Weyrich’s knotweed ( K. weyrichii) has the widest leaves in genus Koenigia. The hybrid that is produced by cross-breeding Koenigia divaricata and Weyrich’s knotweed is known as Finnish knotweed (Koenigia x fennica). Totally different from other genus members is Koenigia islandica.