Flowering shrub

Blueblossom

Ceanothus thyrsiflorus

Blueblossom (Ceanothus thyrsiflorus) is a shrub in the Rhamnaceae family, native in the lower 48 states, blooming mostly February–May across the U.S.

🌷 Flowering shrubNative in the lower 48

Blueblossom is a popular flowering shrub. It's on our flower lists for 3 states, and across the U.S. it's most often seen in bloom in February–May.

2states where USDA records it

3Bloomipedia state lists include it

7,375U.S. sightings*

*iNaturalist research-grade observations, as of October 23, 2026. Our state lists also include states where people grow it in gardens, so they can outnumber USDA's wild-plant records. Planted garden shrubs are mostly excluded from research grade.

On our lists for: California, Oregon, Washington

Quick look

Ceanothus thyrsiflorus, known as blueblossom or blue blossom ceanothus, is an evergreen shrub in the buckthorn family Rhamnaceae that is native to Oregon and California in the western United States and the state of Baja California in northwestern Mexico.
From Wikipedia's article Ceanothus thyrsiflorus, CC BY-SA 4.0.

It belongs to the Rhamnaceae family. ^iNaturalist
USDA PLANTS describes it as a shrub / a tree with a perennial life cycle. ^{USDA PLANTS}
USDA PLANTS lists it as native in the lower 48 states and records it in 2 states. ^{USDA PLANTS}
NatureServe lists it as native to California and Oregon. ^NatureServe
In California, most iNaturalist sightings of it in flower come in February–May. ^iNaturalist
iNaturalist has 7,263 research-grade sightings of it in California, ranking #103 among the 178 flowers on our California list. ^iNaturalist
iNaturalist has 112 research-grade sightings of it in Oregon, ranking #107 among the 184 flowers on our Oregon list. ^iNaturalist

When does it bloom?

Flowering records by month across the U.S. (iNaturalist research-grade observations marked “Flowering”) (1,109 records)

Bloom time in the 3 states whose Bloomipedia list includes it

State	Type	Peak bloom	Sightings*
California	🌷 Garden	February–May	7,263
Oregon	🌷 Garden	few records (33)	112
Washington	🌷 Garden	no flowering records	0

Conservation status

Federal (U.S. ESA): Not listed No U.S. Endangered Species Act listing in the USFWS ECOS database. ^{USFWS ECOS}
NatureServe global: G5 Secure 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)}
Oregon: Not listed Not on Oregon endangered and threatened plants (OAR 603-073-0070). NatureServe: SNR, not yet ranked in Oregon. ^{OAR 603-073-0070}
Washington: No list Washington has no state law listing endangered or threatened plants (the Washington Natural Heritage Program's rare plant list isn't regulatory), so we show NatureServe's Washington ranks instead. NatureServe has no Washington rank for it.
Rare elsewhere: No other U.S. state ranks it S1, S2, SH or SX.

Checked October 23, 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 edibility or poison notes on its page), USDA PLANTS) say whether it's edible or poisonous for people. ^{NC State Extension}

For petsNot well documented

It isn't on the ASPCA plant list, and NC State Extension doesn't flag it for pets.

🌿 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 blueblossom in 2 states.

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recorded by USDA PLANTS on our state lists not recorded

See the full list of states

California, Oregon.

California counties with USDA records: Alameda, Contra Costa, Del Norte, Humboldt, Los Angeles, Marin, Mendocino, Monterey, San Francisco, San Luis Obispo, San Mateo, Santa Barbara, Santa Clara, Santa Cruz, Sonoma.

Oregon counties with USDA records: Benton, Coos, Curry, Douglas, Jackson, Josephine, Lane, Lincoln.

Names, range and relatives

County records: USDA PLANTS lists it in 23 counties across 2 states; the most are in California (15), Oregon (8).

Other Ceanothus on Bloomipedia (3): Snowbrush ceanothus, New Jersey tea, Fendler's ceanothus.

More from the Rhamnaceae family (4 on Bloomipedia; most observed first): Graythorn.

More California flowers

California poppy

Eschscholzia californica

★ CA state flowerNative

🌼 Blooms in CA: March–May

California buckwheat

Eriogonum fasciculatum

Native

🌼 Blooms in CA: April–July

Toyon

Heteromeles arbutifolia

Native

🌼 Blooms in CA: June–August

Sources

USDA, NRCS. PLANTS Database, profile CETH.
iNaturalist, Ceanothus thyrsiflorus: taxonomy, research-grade observation counts and “Flowering” annotations, retrieved October 23, 2026.
Wikipedia, Ceanothus thyrsiflorus (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).
Oregon: Oregon endangered and threatened plants (OAR 603-073-0070).
Oregon: Oregon noxious weed quarantine, A and B weeds (OAR 603-052-1200).
Washington: Washington State noxious weed list (WAC 16-750-005, -011, -015).
USFWS, ECOS species database (ESA listing check), October 23, 2026.
NatureServe Explorer, Ceanothus thyrsiflorus (global and state ranks).
Edibility and toxicity: NC State Extension.
Photo: Henrik Kibak via iNaturalist · CC BY 4.0 · resized.