Flower profile

Cobwebby thistle

Cirsium occidentale

Cobwebby thistle (Cirsium occidentale) is a flowering plant in the Asteraceae family, native in the lower 48 states, blooming mostly April–July across the U.S.

Native to California

Cobwebby thistle is a wildflower that USDA PLANTS lists as native in the lower 48 states. In California it's most often seen in bloom in April–July.

3states where USDA records it

13,492CA sightings*

14,012U.S. sightings*

*iNaturalist research-grade observations, as of October 17, 2026.

On our lists for: California

Quick look

Cirsium occidentale, with the common name cobweb thistle or cobwebby thistle, is a North American species of thistle in the family Asteraceae.
From Wikipedia's article Cirsium occidentale, CC BY-SA 4.0.

It belongs to the Asteraceae family. ^iNaturalist
USDA PLANTS describes it as an herb (forb) with a biennial, perennial life cycle. ^{USDA PLANTS}
USDA PLANTS lists it as native in the lower 48 states and records it in 3 states. ^{USDA PLANTS}
NatureServe lists it as native to California. ^NatureServe
In California, most iNaturalist sightings of it in flower come in April–July. ^iNaturalist
iNaturalist has 13,492 research-grade sightings of it in California, ranking #59 among the 178 flowers on our California list. ^iNaturalist

When does it bloom?

In California, most flowering sightings come in April–July.

Flowering records by month in California (iNaturalist research-grade observations marked “Flowering”) (2,853 records)

Conservation status

Federal (U.S. ESA): Not listed No U.S. Endangered Species Act listing in the USFWS ECOS database. ^{USFWS ECOS}
NatureServe global: G3 Vulnerable worldwide. ^NatureServe
California: Not listed Not on California state-listed endangered, threatened and rare plants (14 CCR § 670.2), per CDFW's CNDDB list (July 2026). NatureServe: SNR, not yet ranked in California. ^{CNDDB listed plants (July 2026)}
Rare elsewhere: No other U.S. state ranks it S1, S2, SH or SX.

Checked October 17, 2026. Rankings and lists can change, so follow the links for the latest.

Can you eat it?

For peopleNot well documented

None of the sources we checked (NC State Extension (no page for this plant), USDA PLANTS) say whether it's edible or poisonous for people.

For petsNot well documented

It isn't on the ASPCA plant list.

🌿 Never eat a wild plant unless you're certain of its ID; this isn't medical advice. Worried about a person? Call Poison Control at 1-800-222-1222. Worried about a pet? Call your vet.

Where does it grow?

USDA PLANTS records cobwebby thistle in 3 states.

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recorded by USDA PLANTS on our state lists not recorded

See the full list of states

California, Nevada, Oregon.

California counties with USDA records: Alameda, Alpine, Amador, Butte, Calaveras, Colusa, Contra Costa, El Dorado, Fresno, Glenn, Humboldt, Inyo, Kern, Lake, Lassen, Los Angeles, Madera, Marin, Mariposa, Mendocino, Merced, Modoc, Mono, Monterey, Napa, Nevada, Orange, Placer, Plumas, Riverside, San Benito, San Bernardino, San Diego, San Francisco, San Luis Obispo, San Mateo, Santa Barbara, Santa Clara, Santa Cruz, Shasta, Sierra, Siskiyou, Solano, Sonoma, Stanislaus, Tehama, Trinity, Tulare, Tuolumne, Ventura, Yolo.

Names, range and relatives

County records: USDA PLANTS lists it in 62 counties across 3 states; the most are in California (51), Nevada (7), Oregon (4).

Other Cirsium on Bloomipedia (12): Bull thistle, Creeping thistle, Bristle thistle, Field thistle, Texas thistle, Wavyleaf thistle, Tall thistle, Elk thistle, New Mexico thistle, Pitcher's thistle.

More from the Asteraceae family (212 on Bloomipedia; most observed first): Common yarrow, Goldenrods, White snakeroot, Sunflowers, Chicory, Black-eyed Susan, Common dandelion, Firewheel.

More California flowers

Common yarrow

Achillea millefolium

Native

🌼 Blooms in CA: April–July

California brittlebush

Encelia californica

Native

🌼 Blooms in CA: January–April

Brittlebush

Encelia farinosa

Native

🌼 Blooms in CA: January–April

Sources

USDA, NRCS. PLANTS Database, profile CIOC.
iNaturalist, Cirsium occidentale: taxonomy, research-grade observation counts and “Flowering” annotations, retrieved October 17, 2026.
Wikipedia, Cirsium occidentale (lead quoted under CC BY-SA 4.0).
California: California state-listed endangered, threatened and rare plants (14 CCR § 670.2), per CDFW's CNDDB list (July 2026).
California: California noxious weed species (3 CCR § 4500).
USFWS, ECOS species database (ESA listing check), October 17, 2026.
NatureServe Explorer, Cirsium occidentale (global and state ranks).
Edibility and toxicity: no source found (marked "not well documented").
Photo: Joey Bom via iNaturalist · CC BY 4.0 · resized.