Persicaria senticosa

Persicaria senticosa is a annual flowering plants in the knotweed family, Polygonaceae. The flower is reddish, bloom between July and August, arrange in headlike inflorescence at the end of the stem. The sphere shaped fruit ripen and become dark black. It has a reddish stem that is armed with downward pointing hooks or barbs which are also present on the underside of the leaf blades.