Shrubs, usually 5–20 dm, green-glabrous or silver-hairy. Cotyledons deciduous, petio­late. Stems ascending or erect, branched, woody. Leaves cau­line; stipules 8–12 mm; petiole 2–3(–6) cm; leaflets 5–12, blades 20–60 × 3–10 mm, adaxial surface glabrous. Peduncles 4–10 cm; bracts deciduous, 8–10 mm. Racemes 10–30 cm; flowers whorled or not. Pedicels 4–10 mm. Flowers 14–18 mm; calyx bulge or spur 0–1 mm, abaxial lobe entire, 5–7 mm, adaxial lobe 2-toothed, 5–9 mm; corolla usually yellow, rarely lilac to purple, banner patch darker or not or white, banner glabrous abaxially, lower keel margins glabrous, adaxial margin ciliate from claw to tip. Legumes 4–7 cm, hairy. Seeds 8–12, black to tan, often striped lighter, 4–5 mm. 2n = 48.

Phenology: Flowering Apr–Jul.
Habitat: Coastal bluffs, dunes, disturbed sand.
Elevation: 0–100 m.

Distribution

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B.C., Calif., Oreg., Wash., Mexico (Baja California), introduced in South America (Argentina, Chile), Europe, Pacific Islands (New Zealand), Australia (including Tasmania).

Discussion

Lupinus arboreus is known from the central California coast southward to northern Baja California; it was introduced as a sand binder and has become naturalized in northern California, Oregon, Washington, and southern British Columbia.

Lupinus arboreus grades into L. rivularis in the North Coast of California. Plants with yellow petals and sweet-smelling flowers are widely cultivated as a sand binder. Hairier plants from the western San Francisco Bay area with yellow banners and blue wings have been called var. eximius; plants with glabrous leaflets and purple petals have been called L. propinquus. Lupinus arboreus hybridizes with L. littoralis and probably other species. Seeds of L. arboreus species are toxic.

Selected References

None.

Lower Taxa

None.