Thlaspi arvense
Fan weed
(c) Mathew* Zappa, some rights reserved (CC BY), uploaded by Mathew* Zappa · licence
Family: Brassicaceae · Type: Herb · Not Native
Thlaspi arvense (Fan weed) is a non-native California herb in the Brassicaceae family, recognized by Only Thlaspi species naturalized in California, European introduction with distinctive fruits.
Fan weed is a naturalized annual found in California in disturbed areas, fields, thickets, bluffs, floodplains, and woodland at elevations below 2,000 meters. Flowering from March to August, this plant produces small white flowers approximately 3 to 4 millimeters long. Growing with glabrous stems 15 to 55 centimeters tall, it develops a distinctive branching structure. Its basal leaves are oblanceolate to obovate, 1 to 5 centimeters long with wavy or toothed margins, while upper stem leaves are sessile. The fruit is uniquely obovate, 0.7 to 2 centimeters wide with a deeply notched tip and distinctive wing-like margins.
Identification and appearance
Key characters: Only Thlaspi species naturalized in California, European introduction with distinctive fruits
Habitat and range
Habitat: Disturbed areas, fields, thickets, bluffs, floodplains, woodland
Elevation: < 2000 m
California counties: Inyo, Lassen, Modoc, Siskiyou, Los Angeles, Fresno, Yolo, San Bernardino, Alpine, Nevada, Sierra, Plumas, Marin, Sonoma, Placer, Shasta, San Mateo, Butte, Napa, Humboldt, San Diego, Alameda, Stanislaus, Sacramento, Monterey
Outside California: North America, native to Europe
Bloom period
Thlaspi arvense blooms Mar-Aug.
How to tell it apart
vs Lepidium: Thlaspi pods are heart-shaped with 2-16 seeds; Lepidium pods are round to oval with only 2 seeds.; vs Caulanthus: Thlaspi has flattened heart-shaped pods; Caulanthus has narrow cylindrical pods.; vs Thelypodium: Thlaspi produces rounded heart-shaped pods; Thelypodium produces elongated linear pods.; vs Brassica: Thlaspi has small heart-shaped flattened pods; Brassica has elongated pods with a distinct beak.; vs Boechera: Thlaspi is annual with heart-shaped pods; Boechera is perennial with long narrow pods.
Frequently asked questions
Is Thlaspi arvense native to California?
No. Thlaspi arvense is not native to California (recorded as not native).
When does Thlaspi arvense bloom?
Thlaspi arvense blooms Mar-Aug.
Where in California does Thlaspi arvense grow?
Thlaspi arvense occurs in Inyo, Lassen, Modoc, Siskiyou, Los Angeles, Fresno, Yolo, San Bernardino and other counties, at elevations of < 2000 m.
What plant family does Thlaspi arvense belong to?
Thlaspi arvense is in the Brassicaceae family, genus Thlaspi.
What habitat does Thlaspi arvense grow in?
Thlaspi arvense grows in Disturbed areas, fields, thickets, bluffs, floodplains, woodland.
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.