BugwoodWiki Article

Conyza canadensis (L.) Cronq.


Conyza canadensis is an annual with a long taproot and one or more stems arising from a basal rosette, normally about 3.3 ft. (1 m) tall.
Leaves are up to 4 in. (10 cm) long and about 0.4 in. (1 cm) wide with some shallow teeth, green with some scattered hairs. Leaf margins ciliate and with longer hairs towards the base of the leaf.
Flower heads are very numerous on short pedicels, only 0.08-0.12 in. (2-3 mm) in diameter. Disc florets are yellow, contrasting with distinct white ray florets which are 0.02-0.04 in. (0.5-1 mm) long.
Fruit is light brown and has tufts of white or light brown hair. Seeds 0.04-0.05 in (1-1.3 mm) long with 10-25 off-white pappus hairs, 0.08-0.16 in. (2-4 mm) long.
Ecological Threat
Conyza canadensis is a common weed in temperate to tropical regions, preferring disturbed sites such as vacant lots, pastures, and on roadsides. This plant is native to North America.

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EDDMapS Distribution - This map is incomplete and is based only on current site and county level reports made by experts, herbaria, and literature. For more information, visit www.eddmaps.org

EDDMapS Distribution

State Invasive List - This map identifies those states that list this species on their invasive species list. For more information, visit Invasive.org

State Invasives List

Most Troublesome / Most Common Agricultural Weed List
This map identifies those states that consider this species either most troublesome or most common in at least one commodity. For more information, visit the MTMC project page.

Most Troublesome and Common Weeds
   No Data for this state
   Troublesome or Common weed in one or more crops

Taxonomic Rank

Kingdom: Plantae
Phylum: Magnoliophyta
Class: Magnoliopsida
Subclass: Asteridae
Order: Asterales
Family: Asteraceae
Genus: Conyza

Other System Links

Plants: COCA5
Bayer: ERICA
GRIN: 104171
ITIS: 37113
NPDN Host: 28137

Synonyms and Other Names

Other Common Names:
Canadian horseweed, Canada horseweed, horseweed, horseweed fleabane, mare's tail, marestail


Category: Forbs/Herbs