Brassica napus
Swede rape, rapeseed, Rapeseed
(c) Pavel Kacl, some rights reserved (CC BY), uploaded by Pavel Kacl · licence
Family: Brassicaceae · Type: Herb · Not Native
Brassica napus (Swede rape) is a non-native California herb in the Brassicaceae family, recognized by strongly lobed/clasping leaf bases and large flowers/fruits.
Swede rape is a naturalized annual found in the San Joaquin Valley and southern California coastal areas in disturbed areas and fields at elevations below 500 meters. Flowering from May to September, this plant produces yellow flowers 10 to 16 millimeters long with petals 6 to 9 millimeters wide. Growing with branched stems 30 to 130 centimeters tall, it has a glabrous or hairy appearance with a glaucous surface. Its leaves are distinctive, with basal leaves pinnately lobed up to 55 centimeters long and middle stem leaves featuring strongly lobed or clasping bases. The fruit develops as an ascending pod 5 to 10 centimeters long with a terminal segment 9 to 16 millimeters in length.
Identification and appearance
Key characters: 5 sympatric species; key features are strongly lobed/clasping leaf bases and large flowers/fruits
Habitat and range
Habitat: Disturbed areas, fields
Elevation: < 500 m
Outside California: widespread North America, native to Europe
Bloom period
Brassica napus blooms May-Sep.
How to tell it apart
vs Hirschfeldia: Brassica pods angle outward with faint veining; Hirschfeldia pods press tight against the stem with prominent ribs.; vs Sisymbrium: Brassica has large showy flowers with petals 8-30mm; Sisymbrium has smaller, less conspicuous flowers.; vs Lactuca: Brassica has four-petaled yellow flowers and seed pods; Lactuca has ray flowers like a dandelion and milky sap.; vs Crambe: Brassica pods split open to release many seeds; Crambe produces single-seeded round fruits that don't split.
Frequently asked questions
Is Brassica napus native to California?
No. Brassica napus is not native to California (recorded as not native).
When does Brassica napus bloom?
Brassica napus blooms May-Sep.
What plant family does Brassica napus belong to?
Brassica napus is in the Brassicaceae family, genus Brassica.
What habitat does Brassica napus grow in?
Brassica napus grows in Disturbed areas, fields.
Related species
Other California species in the same genus, family, or bioregion.
Sources: Jepson eFlora · 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.