Erigeron canadensis
Horseweed, Horseweed
(c) Scott Morris, some rights reserved (CC BY), uploaded by Scott Morris · licence
Family: Asteraceae · Type: Annual · Native
Erigeron canadensis (Horseweed) is a native California annual in the Asteraceae family, recognized by distinctive tall annual with numerous small heads and tiny rays.
Horseweed is a California native annual found in disturbed places throughout the state at elevations generally below 2,300 meters. Flowering all year, this plant produces white to pink ray flowers in small heads less than 4 millimeters wide, arranged in panicle-like clusters. Growing with erect stems 20 to 200 centimeters tall, it is very leafy with branches spreading throughout the upper portion of the plant. Its leaves are linear to oblanceolate, ranging from 2 to 5 centimeters long, with entire or slightly toothed margins and sparse bristly hairs. The fruit is a small tan to light gray-brown seed topped with 15 to 25 white pappus bristles.
Identification and appearance
Key characters: 82 sympatric species; distinctive tall annual with numerous small heads and tiny rays
Habitat and range
Habitat: Disturbed places
Elevation: generally < 2300 m
Outside California: to British Columbia, eastern North America, Central America, introduced +- worldwide
Bloom period
Erigeron canadensis blooms All year.
How to tell it apart
vs Bellis: Erigeron has double-layered pappus (outer scales + inner bristles); Bellis completely lacks pappus.; vs Symphyotrichum: Erigeron has double pappus (2 layers); Symphyotrichum has single layer of uniform bristles.; vs Corethrogyne: Erigeron has simple unbranched stems; Corethrogyne has branched stems.; vs Pseudognaphalium: Erigeron has flat button-like flower heads; Pseudognaphalium has woolly clustered heads without rays.; vs Artemisia: Erigeron has obvious ray petals around yellow disk; Artemisia lacks ray petals entirely.
Frequently asked questions
Is Erigeron canadensis native to California?
Yes. Erigeron canadensis is native to California (recorded as native).
When does Erigeron canadensis bloom?
Erigeron canadensis blooms All year.
What plant family does Erigeron canadensis belong to?
Erigeron canadensis is in the Asteraceae family, genus Erigeron.
What habitat does Erigeron canadensis grow in?
Erigeron canadensis grows in Disturbed places.
Related species
Other California species in the same genus, family, or bioregion.
Sources: Jepson eFlora · Index of California Plant Names · CalPhotos
Last updated 2026-10-06
Data from The California Species Project — 14,000+ California species with verified data from CNPS, CDFW, USFWS, Cal-IPC, and more.