Heracleum maximum
Cow parsnip, giant hogweed, Giant Hogweed
(c) Rosario, some rights reserved (CC BY), uploaded by Rosario · licence
Family: Apiaceae · Type: Herb · Native
Heracleum maximum (Cow parsnip) is a native California herb in the Apiaceae family, recognized by No sympatric species - geographically isolated. Distinguished by large size, ternate leaves, and white umbels.
Cow parsnip is a native perennial found in the California Floristic Province and Great Basin in moist places, wooded or open, at elevations up to 2,900 meters. Flowering from April to July, this plant produces large white flowers in wide, complex clusters with multiple unequal rays. Growing 1 to 3 meters tall with a stout, strong-scented stem, the plant has a robust and impressive presence in its habitat. Its distinctive leaves are large and compound, with broad ternate blades up to 5 decimeters wide, divided into ovate to round leaflets that are deeply lobed and coarsely serrated. The fruit is obovate to obcordate, approximately 8 to 12 millimeters long and slightly hairy.
Identification and appearance
Key characters: No sympatric species - geographically isolated. Distinguished by large size, ternate leaves, and white umbels.
Habitat and range
Habitat: Moist places, wooded or open
Elevation: < 2900 m
California counties: Humboldt, San Bernardino, Fresno, Alameda, Madera, Shasta, Mendocino, Butte, Mariposa, Placer, San Mateo, El Dorado, Tulare, Alpine, Trinity, Marin, Mono, Tuolumne, San Diego, Nevada, Tehama, Los Angeles, Sonoma, San Luis Obispo, Modoc, Plumas, Inyo, San Francisco, Santa Cruz, Siskiyou, Amador, Contra Costa, Del Norte, Napa, Santa Clara, Sierra, Monterey
Outside California: to Alaska, eastern United States, Arizona
Bloom period
Heracleum maximum blooms Apr-Jul.
How to tell it apart
vs Angelica: Heracleum has dramatically enlarged outer petals creating irregular flower clusters; Angelica has uniform petals.; vs Conium: Heracleum has white stems and enlarged outer petals; Conium has purple-spotted stems and uniform petals.; vs Petasites: Heracleum has compound leaves and umbrella flower clusters; Petasites has simple round leaves and daisy-like flowers.; vs Acanthus: Heracleum has umbrella-shaped flower clusters; Acanthus has tall spikes of hooded flowers.; vs Anthriscus: Heracleum is massive (3-10 feet) with enlarged outer petals; Anthriscus is smaller with uniform petals.
Frequently asked questions
Is Heracleum maximum native to California?
Yes. Heracleum maximum is native to California (recorded as native).
When does Heracleum maximum bloom?
Heracleum maximum blooms Apr-Jul.
Where in California does Heracleum maximum grow?
Heracleum maximum occurs in Humboldt, San Bernardino, Fresno, Alameda, Madera, Shasta, Mendocino, Butte and other counties, at elevations of < 2900 m.
What plant family does Heracleum maximum belong to?
Heracleum maximum is in the Apiaceae family, genus Heracleum.
What habitat does Heracleum maximum grow in?
Heracleum maximum grows in Moist places, wooded or open.
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.