''Polygonum engelmannii'', common name Engelmann's knotweed, is a North American species of plants in the

buckwheat family The Polygonaceae are a family of flowering plants known informally as the knotweed family or smartweed—buckwheat family in the United States. The name is based on the genus ''Polygonum'', and was first used by Antoine Laurent de Jussieu in 1789 ...

. It is native to western Canada and the western United States, usually at high elevations in the mountains. It has been found in Alberta, British Columbia, Idaho, Montana, Wyoming, Nevada, Utah, and Colorado. ''Polygonum engelmannii'' is an branching herb up to 30 cm (1 foot) tall. It has clusters of green or purple flowers.Flora of North America, ''Polygonum engelmannii'' Greene, 1885. (as ''engelmanni).'' Engelmann's knotweed
/ref>Greene, Edward Lee. 1885. Bulletin of the California Academy of Sciences 1(3): 126
/ref>

References

engelmannii Flora of Western Canada Flora of the Western United States Flora of the Rocky Mountains Plants described in 1885 Taxa named by Edward Lee Greene {{Polygonaceae-stub