Conyza Canadensis

Horseweed, mare’s tail, Canada fleabane, butter weed

Description: winter or summer annual

Place of origin: North America

Urban habitat: grows well in dry sites with full sun; common in vacant lots, abandoned grasslands, rock outcrops, stone walls, rubble dumps, fence lines, highway banks and median strips, and in cracks in pavement.

Ecological function: disturbance-adapted colonizer of bare ground.

History: Conyza Canadensis is native to North America but was introduced in temperate Europe and Asia where it has spread widely. The Shakers used C. Canadensis as a treatment for kidney stones and a variety of bowel and urination problems. Native Americans boiled the plant for steam in sweat lodges, used it as snuff for treatment of colds, and burned it to ward off insects. It is currently used in homeopathic medicines for treatment of gastro-intestinal problems, including diarrhea and dysentery and bleeding hemorrhoids. It is also known to be an astringent, and useful for treatment of rheumatism. A tea of the boiled roots is used to treat menstrual irregularities and pain. Its cooked young leaves and seedlings can be consumed and it is the source of an essential oil used commercially for flavoring sweets, condiments and soft drinks.