Canadian fleabane (Erigeron canadensis) — identification, habitat & look-alikes

Canadian fleabane is an native to North America that grows in fields, orchards, roadsides, and vacant lots throughout the United States. A single plant can produce more than 200,000 tiny seeds that ride the wind. Canadian fleabane is also called horseweed.

Appearance

Growth form: This winter or summer annual has one upright, hairy stem that can reach 6 ft (1.8 m) or more.
Leaves: Young plants form a low of hairy leaves. The mature stem is crowded with narrow leaves that grow on alternating sides; it branches mainly in its upper half.
Flowers: Many tiny white flower heads with yellowish centers form on the upper branches.
Flowering time: In California, flowers bloom from June through September.
Fruit: Each tiny dry fruit carries a of fine bristles, making the mature heads look like miniature dandelion puffs.

Look-alikes

Hairy FleabaneErigeron bonariensis

Hairy fleabane is usually shorter, grayer, and more densely hairy, with several branches starting near the base. Horseweed is greener and usually has one main stem that branches mostly in the upper half; seedlings may be hard to separate.

Why they get mixed upBoth are narrow-leaved annual weeds with many tiny flower heads.

Annual FleabaneErigeron annuus

Annual fleabane has flower heads about two to three times wider, with much more obvious white petal-like parts. Its leaves are broader and more distinctly toothed than horseweed leaves.

Why they get mixed upBoth are upright Erigeron species with white daisy-like flowers.

Where it lives

Typical habitats: crop fields and orchards
roadsides and vacant lots
nurseries and landscapes
Range: It is native to North America and widespread in the United States. It is especially common where soil is disturbed and mowing or cultivation is infrequent.
Preferred conditions: It can germinate in fall or spring and grows in both moist and fairly dry soils. Fall seedlings often overwinter as a rosette.
Flowering: Flowers Jun–Sep
Flowers Jun–Sep

Life cycle

Reproduction: The plant reproduces only by seed, with both fall-emerging and spring-emerging life cycles.
Seed dispersal: The tiny fruits have fine bristles that let the wind carry them away.

Name and classification

About the name: It has also been called Conyza canadensis.

Conservation

IUCN Red List: NENot EvaluatedNot yet assessed
Threats: Horseweed competes with crops and can be difficult to control in fields that are not plowed, orchards, and nurseries. has developed in some populations.

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