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Plant Database

Search for native plants by scientific name, common name or family. If you are not sure what you are looking for, try the Combination Search or our Recommended Species lists.

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Conyza canadensis (Horseweed)
Romfh, Peggy

Conyza canadensis

Conyza canadensis (L.) Cronquist

Horseweed, Canadian Horseweed

Asteraceae (Aster Family)

Synonym(s):

USDA Symbol: coca5

USDA Native Status: L48 (N), AK (I), HI (I), PR (N), VI (N), CAN (N), SPM (N)

A coarse weed with erect bristly-haired stem that has branching clusters of small, cup-like, greenish-white flower heads arising from upper leaf axils. The minute white rays do not spread and thus are not showy; the numerous disc flowers are yellow.

An annual that thrives on bare soil, Horseweed is soon crowded out as perennials become established. Originally a North American plant, it has spread to Europe, where it colonizes open disturbed sites. Indians and early settlers used a preparation of its leaves to treat dysentery and sore throat.

 

From the Image Gallery

13 photo(s) available in the Image Gallery

Plant Characteristics

Duration: Annual
Habit: Herb
Size Notes: Up to about 6 feet tall. Occasionally up to almost 12 feet tall.
Leaf: Green
Fruit: Fruit is a cypsela (pl. cypselae). Though technically incorrect, the fruit is often referred to as an achene.

Bloom Information

Bloom Color: White , Yellow , Purple
Bloom Time: Jan , Feb , Mar , Apr , May , Jun , Jul , Aug , Sep , Oct , Nov , Dec
Bloom Notes: White to pale purplish small ray flowers, yellow disc flowers. Flowers mostly summer through fall. May flower year-round in the right conditions.

Distribution

USA: AL , AR , AZ , CA , CO , CT , DC , DE , FL , GA , IA , ID , IL , IN , KS , KY , LA , MA , MD , ME , MI , MN , MO , MS , MT , NC , ND , NE , NH , NJ , NM , NV , NY , OH , OK , OR , PA , RI , SC , SD , TN , TX , UT , VA , VT , WA , WI , WV , WY
Canada: AB , BC , MB , NB , NL , NS , NT , ON , PE , QC , SK
Native Distribution: Throughout North America, except parts of far north.
Native Habitat: Fields, roadsides, and waste places.

Growing Conditions

Water Use: Medium
Light Requirement: Sun
CaCO3 Tolerance: Low

Benefit

Conspicuous Flowers: yes

From the National Organizations Directory

According to the species list provided by Affiliate Organizations, this plant is on display at the following locations:

Pineywoods Native Plant Center - Nacogdoches, TX
Sibley Nature Center - Midland, TX
Brackenridge Field Laboratory - Austin, TX
Stengl Biological Research Station - Smithville, TX

Wildflower Center Seed Bank

LBJWC-0148 Collected 2007-09-04 in Travis County by Lady Bird Johnson Wildflower Center

1 collection(s) available in the Wildflower Center Seed Bank

Web Reference

Webref 38 - Flora of North America (2019) Missouri Botanical Garden, St. Louis, MO & Harvard University Herbaria, Cambridge, MA.
Webref 23 - Southwest Environmental Information Network (2009) SEINet - Arizona Chapter

Additional resources

USDA: Find Conyza canadensis in USDA Plants
FNA: Find Conyza canadensis in the Flora of North America (if available)
Google: Search Google for Conyza canadensis

Metadata

Record Modified: 2022-12-06
Research By: TWC Staff

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