Mercurialis annua
Annual mercury
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Family: Euphorbiaceae · Type: Herb · Not Native
Mercurialis annua (Annual mercury) is a non-native California herb in the Euphorbiaceae family, recognized by Recent European introduction with limited California distribution.
Annual mercury is a naturalized annual found in the San Francisco Bay Area in open, disturbed areas at elevations below 200 meters. Flowering from February to October, this plant produces small, inconspicuous flowers with green staminate and pistillate clusters. Growing with slender stems 10 to 30 centimeters tall, it spreads quickly in disturbed landscapes. Its leaves are ovate, 2 to 5 centimeters long, with serrated edges and ciliate margins, attached to short petioles. The fruit is small, approximately 2 to 3 millimeters in diameter, with shiny, pitted seeds.
Identification and appearance
Key characters: Recent European introduction with limited California distribution
Habitat and range
Habitat: Open, disturbed areas
Elevation: < 200 m
California counties: San Mateo, Alameda, Riverside, Santa Barbara, Santa Cruz, Yolo, Marin, San Luis Obispo, Santa Clara
Outside California: native to Europe
Bloom period
Mercurialis annua blooms Feb-Oct.
How to tell it apart
vs Euphorbia: Mercurialis has opposite leaves; Euphorbia has alternate or whorled leaves.; vs Galium: Mercurialis has opposite toothed leaves; Galium has whorled simple leaves with smooth edges.
Frequently asked questions
Is Mercurialis annua native to California?
No. Mercurialis annua is not native to California (recorded as not native).
When does Mercurialis annua bloom?
Mercurialis annua blooms Feb-Oct.
Where in California does Mercurialis annua grow?
Mercurialis annua occurs in San Mateo, Alameda, Riverside, Santa Barbara, Santa Cruz, Yolo, Marin, San Luis Obispo and other counties, at elevations of < 200 m.
What plant family does Mercurialis annua belong to?
Mercurialis annua is in the Euphorbiaceae family, genus Mercurialis.
What habitat does Mercurialis annua grow in?
Mercurialis annua grows in Open, disturbed areas.
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.