Geranium robertianum
Robert geranium
(c) Borja Fierro, some rights reserved (CC BY), uploaded by Borja Fierro · licence
Family: Geraniaceae · Type: Herb · Not Native
Geranium robertianum (Robert geranium) is a non-native California herb in the Geraniaceae family, recognized by highly dissected leaves and purplish anthers.
Robert geranium is a naturalized annual plant found in northern coastal, central coastal, and San Francisco Bay Area regions in open to shaded sites at elevations below 500 meters. Flowering throughout the year, this plant produces delicate pink to red-purple flowers 10.5 to 12.5 millimeters long with rounded petals. Growing with decumbent to ascending stems 10 to 50 centimeters tall and 1 to 3 millimeters wide, it has sparse hairs along the stem. Its distinctive leaves are deeply divided into 5 segments, each pinnately lobed with the middle segment having 16 to 37 lobes in the upper half. The fruit is characterized by a long 17 to 19 millimeter beak with a narrow 4 to 5 millimeter tip.
Identification and appearance
Key characters: 15 sympatric species; distinguished by highly dissected leaves and purplish anthers
Habitat and range
Habitat: Open to shaded sites
Elevation: < 500 m
California counties: Mariposa, Alameda, Los Angeles, Riverside, Calaveras, Sonoma, Santa Cruz, Amador, Marin, Solano, Monterey, San Francisco, Santa Clara, Contra Costa, Del Norte, Napa, San Mateo, San Luis Obispo
Outside California: widespread North America, native to Europe, northern Africa, western Asia, alien in South America, China, Madagascar
Bloom period
Geranium robertianum blooms All year.
How to tell it apart
vs Erodium: Geranium leaves are palmately divided like spread fingers; Erodium leaves are pinnately divided like a feather.; vs Pelargonium: Geranium is herbaceous with symmetrical flowers; Pelargonium is shrubby with asymmetrical flowers.; vs Sidalcea: Geranium has deeply palm-divided leaves; Sidalcea has shallowly palmately-lobed leaves and stamens fused in a column.; vs Bowlesia: Geranium has deeply divided leaves and pink flowers; Bowlesia has shallowly lobed leaves and tiny white umbel flowers.; vs Malva: Geranium has deeply palm-divided leaves with narrow segments; Malva has shallowly palmately-lobed leaves and fused stamens.
Frequently asked questions
Is Geranium robertianum native to California?
No. Geranium robertianum is not native to California (recorded as not native).
When does Geranium robertianum bloom?
Geranium robertianum blooms All year.
Where in California does Geranium robertianum grow?
Geranium robertianum occurs in Mariposa, Alameda, Los Angeles, Riverside, Calaveras, Sonoma, Santa Cruz, Amador and other counties, at elevations of < 500 m.
What plant family does Geranium robertianum belong to?
Geranium robertianum is in the Geraniaceae family, genus Geranium.
What habitat does Geranium robertianum grow in?
Geranium robertianum grows in Open to shaded sites.
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.