Ageratina adenophora
Crofton weed, Crofton Weed
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Family: Asteraceae · Type: Subshrub · Not Native
Conservation status: Cal-IPC Yes
Ageratina adenophora (Crofton weed) is a non-native California subshrub in the Asteraceae family.
Crofton weed is a naturalized perennial herb found in coastal California regions including the Central Coast, San Francisco Bay Area, southern coastal ranges, and southwestern California in disturbed places, streambanks, canyons, and hillslopes at elevations below 1,000 meters. Flowering throughout the year, this plant produces white or pink-tinged flowers in small heads approximately 6.5 millimeters long. Growing with erect stems 50 to 150 centimeters tall that are purplish and glandular-hairy, it develops a woody base. Its opposite leaves are large, 40 to 100 millimeters long, with deltate-ovate shapes, serrated edges, and a distinctive purple upper surface that is glandular-puberulent. The fruit is small, measuring 1.7 to 2 millimeters in length.
Identification and appearance
Key characters: 0 sympatric species - geographically isolated
Habitat and range
Habitat: Disturbed places, streambanks, canyons, hillslopes
Elevation: < 1000 m
Outside California: native of Mexico, widely naturalized
Bloom period
Ageratina adenophora blooms All year.
Conservation status
Cal-IPC Yes
How to tell it apart
vs Baccharis: Ageratina has opposite leaves and bisexual flowers; Baccharis has alternate leaves and separate male/female plants.; vs Spiraea: Ageratina has composite flower heads; Spiraea has individual 5-petaled flowers in branched clusters.; vs Venegasia: Ageratina has white rayless flowers; Venegasia has large yellow ray petals and huge triangular leaves.; vs Eupatorium: Same genus (Eupatorium is old name); plants are identical.; vs Scrophularia: Ageratina has composite flower heads; Scrophularia has tubular two-lipped flowers typical of figworts.
Frequently asked questions
Is Ageratina adenophora native to California?
No. Ageratina adenophora is not native to California (recorded as not native).
When does Ageratina adenophora bloom?
Ageratina adenophora blooms All year.
What plant family does Ageratina adenophora belong to?
Ageratina adenophora is in the Asteraceae family, genus Ageratina.
Is Ageratina adenophora invasive in California?
Ageratina adenophora is listed by Cal-IPC with an invasiveness rating of Yes.
What habitat does Ageratina adenophora grow in?
Ageratina adenophora grows in Disturbed places, streambanks, canyons, hillslopes.
Related species
Other California species in the same genus, family, or bioregion.
Sources: Jepson eFlora · Index of California Plant Names · CalPhotos
Last updated 2026-10-07
Data from The California Species Project — 14,000+ California species with verified data from CNPS, CDFW, USFWS, Cal-IPC, and more.