Horseweed

Erigeron canadensis syn. Conyza canadensis

Butterweed Canadian Fleabane Colt's-tail Fleabane Hogweed Horseweed Parts used Uses Habitat and cultivation Constituents

Horseweed - an annual weed with an erect downy stem growing up to 7 feet tall and coming out of a tuft of basal leaves that later wilt. Dark green lance-shaped alternate leaves are sometimes toothed and have scattered coarse white hairs. Numerous small flower heads (July-November) in loose clusters have tiny yellow central disc flowers and minute greenish-white to lavender petal like ray flowers. The flowers are followed by white-tufted, one-seeded dry fruits, or achenes.

Strictly a North American weed at one time, horseweed (or fleabane, as it is often called) was introduced as a medicinal plant by American Indians to early settlers in the New World. Word of its attributes reached John Parkinson, herbalist to King Charles I of England. He described horseweed in 1640 as an American species. Thirteen years later in France, horseweed was listed in an inventory of plants found in Paris's Jardin des Plantes, or botanical gardens. To explain its presence, French botanists proposed that the seeds might have been imported from Canada with beaver skins or stuffed birds. Horseweed, it appears, has spread ever since, because horseweed is now reported growing in many parts of the world.

North American Indians favored an extract from the boiled leaves (a decoction) to treat dysentery. Later, horseweed was used as a diuretic, as a tonic, and as an astringent to stop bleeding. Herbals still specify horseweed for these uses. It is most likely called horseweed because of its large size in comparison to other related species. The herb may have been given the name fleabane because it produces a turpentine like oil that repels fleas or because the plant's tiny seeds look like fleas.

PARTS USED

Aerial parts.

USES

An astringent herb, horseweed is taken for gastrointestinal problems such as diarrhea and dysentery. A decoction of horseweed is reportedly a very effective treatment for bleeding hemorrhoids. The herb is occasionally used as a diuretic for bladder problems, to clear toxins in rheumatic conditions, and to treat gonorrhea and other urinogenital diseases.

The essential oil in the leaves of horseweed has traditionally been employed as a hemostatic, or agent that helps arrest the flow of blood. Pharmacologists believe that horseweed may be effective in stopping external bleeding because of its tannin content. Scientific studies have validated the plant's use as an insecticide.

HABITAT AND CULTIVATION

Native to North America, horseweed is now common in South America and Europe. Horseweed thrives on uncultivated and recently cleared land, often invading in large swathes. Horseweed is gathered from the wild when in flower.

CONSTITUENTS

Horseweed contains a volatile oil (including limonene, terpineol, and linalool), flavonoids, terpenes, plant acids, and tannins.