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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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