urbpan | 365 Urban Species. #139: Horseweed

Urban species #139: Horseweed Conyza canadensis

When I imagine a weed, I imagine horseweed. Dandelion is charming, and garlic mustard is sinister, but horseweed is nondescript and ubiquitous. I have seen this plant (a member of the fleabane group, in the aster family) grow in sidewalk cracks, abandoned window boxes, and, fittingly, horse pastures. A native North American plant, it has been prized as an herbal medicine ingredient since prehistory, and was introduced to Eurasia in the 1600's. Horseweed is the only North American plant on the list of the top ten weeds of the northern hemisphere. Its inconspicuous flowers, as well as its propensity to grow in waste areas, give strength to this plant's designation as a weed.