Practical ecological knowledge for the temperate reader.

Conyza canadensis - Horseweed

Family: Asteraceae (Aster) [E-flora]

Other Names: (Canadian fleabane; Canadian horseweed) [E-flora]

"Conyza canadensis is a ANNUAL growing to 1 m (3ft 3in) by 0.5 m (1ft 8in).
It is hardy to zone (UK) 7. It is in flower from Jun to October, and the seeds ripen from Jul to October. The flowers are hermaphrodite (have both male and female organs) and are pollinated by Bees, flies.It is noted for attracting wildlife.
Suitable for: light (sandy) and medium (loamy) soils and prefers well-drained soil. Suitable pH: neutral and basic (alkaline) soils. It can grow in semi-shade (light woodland) or no shade. It prefers dry or moist soil and can tolerate drought." [PFAF]

"General: Annual herb from a taproot; stems erect, usually single, more or less glabrous, 0.2-1.0 m tall." [IFBC-E-flora]
"Leaves: Basal leaves lacking; stem leaves linear to linear-lanceolate or the lowermost oblanceolate, stalked, 2-10 cm long, 2-8 mm wide, glabrous." [IFBC-E-flora]
"Flowers: Heads with ray and disk flowers, numerous in an open, leafy, branched, usually cylindric inflorescence; involucres 3-4 mm tall; involucral bracts graduated, glabrous to sparsely stiff-hairy, with a conspicuous central glandular area and narrow, more or less papery margins; ray flowers white, numerous, inconspicuous, barely exceeding the pappus; disk flowers few." [IFBC-E-flora]
"Fruits: Achenes stiff-hairy; pappus of dirty-whitish, slender hairs." [IFBC-E-flora]

"Habitat / Range Mesic to dry roadsides and disturbed areas in the lowland, steppe and montane zones; frequent in S BC; introduced, native range uncertain." [IFBC-E-flora]

Origin Status: Native [E-flora]


Edible Uses

Other Uses

Medicinal Uses

"In traditional North American herbal medicine, Canada fleabane was boiled to make steam for sweat lodges, taken as a snuff to stimulate sneezing during the course of a cold and burned to create a smoke that warded off insects[254]. Nowadays it is valued most for its astringency, being used in the treatment of gastro-intestinal problems such as diarrhoea and dysentery[254]. It is said to be a very effective treatment for bleeding haemorrhoids[254]." [PFAF]


"The whole plant is antirheumatic, astringent, balsamic, diuretic, emmenagogue, styptic, tonic and vermifuge[4, 7, 9, 21, 222]." [PFAF]

"Activities (Horseweed) — Anticonvulsant (f; DEM); Antiedemic (f; PH2); Antiinflammatory (f; PHR); Astringent (f; FAD); Diaphoretic (f; DEM); Diuretic (f; FAD); Hemostat (f; PHR); Hypotensive (1; PNC); Sternutator (f; DEM); Tonic (f; PNC); Vermifuge (f; PHR)." [PFAF]


Horseweed – Conyza canadensis [PFAF]

Part: Leaves Per 100 g Dry weight
Food Energy (Kcal) - Ash (g) 8.2 Potassium (mg) 2610
Water (g) - Thiamine (mg) - Magnesium (mg) -
Protein (g) 14.9 Riboflavin (mg) - Calcium (mg) 1010
Fat (g) 1.8 Niacin (mg) - Phosphorus (mg) 280
Carbohydrate (g) 75.1 Vitamin C (mg) - Sodium (mg) -
Fiber (g) 26.1 Vitamin A (RE) - Iron (mg) -
Zinc (mg) - Manganese (mg) - Copper (mg) -

"Prefers a well-drained light or medium neutral to alkaline soil in a sunny position, though it tolerates most conditions[238]. Originally from N. America, Canada fleabane has become naturalized in many areas of the world and is considered to be a nuisance weed in many areas[268]. The plant is very adaptable to differing conditions and can vary dramatically in height, from only a few centimetres in poor soils to as much as 3 metres tall in rich soils[213]. The plant is used commercially as a food flavouring[183]. A good bee plant[200] but unfortunately it also harbours various insect pests such as the tarnished plant bug[1]." [PFAF]

"Seed - we have no information on this species but suggest sowing the seed in spring in situ. An autumn sowing in situ might also be worthwhile." [PFAF]



Page last modified on Wednesday, March 23, 2022 6:38 PM