Horseweed

Fifty or so annuals and perennials comprise this N America genus, which is widely naturalized in Europe, Asia, Australia, and various Pacific islands. Conyza canadensis is a common American weed that reached Europe in the 17th century. Recorded at the Botanic Garden in Blois (N France) in 1653, it spread to all parts within 30 years, and arrived in England in 1690. Having no ornamental merit, it was presumably first imported as a medicinal plant. Conyza canadensis was a native N American herb before entering the U.S. Pharmacopoeia (1836-1916). It was used by various tribes, including the Houma, Ojibwa, Meskwaki, Catawba, and Cree, to deter insects (hence the name "Canadian fleabane") and to cure diarrhea, hemorrhage, and menstrual irregularities. Conyza bonariensis, originally from tropical America, is naturalized in N Africa, where the flowering plant is used as a diuretic and anti-rheumatic.

Tall annual with narrowly oblanceolate leaves to 10cm (4in) long. Panicles of tiny, thistle-like, flowers, with green-white to pale mauve ray florets and yellow disks, appear in late summer and early autumn.


Common Name:
Horseweed
Other Names:
Canadian fleabane
Botanical Name:
Conyza canadensis syn Erigeron canadensis
Genus:
Conyza
Family:
Asteraceae
Native Location:
Tropical America and USA to S Canada; Widely naturalized
Cultivation:
Light sandy soil in sun. Tolerates most conditions, varying in size accordingly.
Propagation:
By seed sown in spring.
Harvest:
Plants are cut when in flower and are best used fresh for oil extraction and liquid extracts. They may also be frozen or made into syrup. Dried herb deteriorates within a year.
Height:
1.5m (5ft)
Width:
45cm (18in)
Hardiness:
Hardy
Parts Used:
Whole plant, oil
Properties:
A slightly aromatic, bitter, tonic herb that acts as a diuretic, and checks bleeding.
Medicinal Uses:
Internally for diarrhea, hemorrhage, kidney disorders, and bronchial complaints. Externally for eczema and ringworm.
Culinary Uses:
Young leaves plants are cooked as a vegetable.
Economic Uses:
Essential oil is used for flavoring candy, condiments, and soft drinks.
Bibliography:
Encyclopedia of herbs by Deni Brown Copyright © 1995, 2001 Dorling Kindersley Limited. pg 178-179