Erigeron canadensis L.
Synonym: Leptilon canadense (L.) Britton.
Other common names: Erigeron, mare's-tail, Canada erigeron, butterweed, bitterweed, cow's-tail, colt's-tail, fireweed, bloodstanch, hogweed, prideweed, scabious.
Habitat and range: Horseweed is common in fields and waste places and along roadsides throughout almost all of North America.
Description: This weed varies greatly in height according to the soil it grows in. The erect stem, sometimes smooth, but usually bristly hairy, is generally branched near the top. The leaves are usually somewhat hairy, the lower ones 1 to 4 inches long and toothed, those scattered along the stem are rather narrow and smooth. From June to November the plant produces numerous heads of small, inconspicuous white flowers, followed by an abundance of seed.
Part used: The entire herb, collected during the flowering period. Oil of erigeron, obtained from the plant by distillation, is produced commercially in Michigan and Indiana.
