Flower profile
Milk thistle
Silybum marianum
Milk thistle is a wildflower that USDA PLANTS lists as introduced in the lower 48 states. In California it's most often seen in bloom in April–June.
*iNaturalist research-grade observations, as of October 17, 2026.
On our lists for: California
Quick look
Silybum marianum is a species of thistle. It has various common names including milk thistle, blessed milkthistle, Marian thistle, Mary thistle, Saint Mary's thistle, Mediterranean milk thistle, variegated thistle and Scotch thistle. This species is an annual or biennial plant of the family Asteraceae. This fairly typical thistle has red to purple flowers and shiny pale green leaves with white veins.
- It belongs to the Asteraceae family. iNaturalist
- USDA PLANTS describes it as an herb (forb) with a annual, biennial life cycle. USDA PLANTS
- USDA PLANTS lists it as introduced in the lower 48 states and records it in 26 states. USDA PLANTS
- NatureServe lists it as not native to California. NatureServe
- In California, most iNaturalist sightings of it in flower come in April–June. iNaturalist
- iNaturalist has 16,899 research-grade sightings of it in California, ranking #36 among the 110 flowers on our California list. iNaturalist
Milk thistle gift ideas
Handmade milk thistle gifts from independent makers.
🌱 Sample spot. Handmade gift picks from independent shops will appear here once our shop partnership is approved. These cards are placeholders, not real products.
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Milk thistle art print
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Milk thistle greeting card
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Milk thistle mug
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Milk thistle earrings
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Milk thistle embroidery pattern
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Milk thistle sticker
When does it bloom?
In California, most flowering sightings come in April–June.
Conservation status
- Federal (U.S. ESA)
- Not listed No U.S. Endangered Species Act listing in the USFWS ECOS database. USFWS ECOS
- NatureServe global
- GNR Not yet ranked 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: SNA, not applicable (usually because it isn't native there) 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?
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.
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 milk thistle in 26 states plus Washington, D.C.
recorded by USDA PLANTS on our state lists not recorded
See the full list of states
Alabama, Arizona, Arkansas, California, Colorado, Connecticut, Georgia, Indiana, Louisiana, Maryland, Massachusetts, Michigan, Mississippi, Nevada, New Hampshire, New Mexico, New York, Ohio, Oklahoma, Oregon, Pennsylvania, Tennessee, Texas, Virginia, Washington, West Virginia; District of Columbia.
California counties with USDA records: Alameda, Amador, Butte, Contra Costa, Glenn, Humboldt, Kern, Los Angeles, Madera, Marin, Mendocino, Merced, Monterey, Napa, Nevada, Orange, Plumas, Riverside, Sacramento, San Diego, San Francisco, San Joaquin, San Luis Obispo, San Mateo, Santa Barbara, Santa Clara, Solano, Sonoma, Stanislaus, Tehama, Tuolumne, Ventura, Yolo.
More California flowers
Sources
- USDA, NRCS. PLANTS Database, profile SIMA3.
- iNaturalist, Silybum marianum: taxonomy, research-grade observation counts and “Flowering” annotations, retrieved October 17, 2026.
- Wikipedia, Silybum marianum (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, Silybum marianum (global and state ranks).
- Edibility and toxicity: no source found (marked "not well documented").
- Photo: Anne Parsons via iNaturalist · CC0 · resized.