Polygonum achoreum

Polygonum achoreum, common names Blake's knotweed, leathery knotweed or striate knotweed, is a North American species of plants in the buckwheat family. It is widespread across much of Canada and the northern United States.

Polygonum achoreum is an herb up to 70 cm (28 in) tall with yellow-green flowers in flat-topped clusters.