Lupinus rivularis

Herbs, perennial, 3.5–10 dm, green, ± glabrous. Cotyledons deciduous, petiolate. Stems decumbent, ascending, or erect, branched, dark brown to red, usually hollow. Leaves cauline; stipules 7–15 mm; petiole 3–5 cm; leaflets 5–9, blades 20–40 × 4–9 mm, adaxial surface glabrous. Peduncles 3–15 cm; bracts deciduous, 8–10 mm. Racemes open, 15–50 cm; flowers ± whorled or not. Pedicels 5–10 mm. Flowers 12–16 mm; calyx bulge or spur 0–1 mm, abaxial lobe entire or ± 3-toothed, 7–9 mm, adaxial lobe 2-toothed, 7–8 mm; corolla violet, banner glabrous abaxially, lower keel margins glabrous, adaxial margin ciliate claw to tip. Legumes dark, 3–7 cm, sparsely hairy. Seeds 7 or 8, mottled brown with black line, 3–4 mm.

Phenology: Flowering Mar–Jun.
Habitat: Gravelly prairies, open woods, riverbanks.
Elevation: 0–500 m.

B.C., Calif., Oreg., Wash.

Discussion

Lupinus rivularis ranges from Mendocino County in California northward through Oregon and Washington. It has been confirmed in British Columbia (where it is of conservation concern) in the extreme southwestern corner of the province, with a single population on southern Vancouver Island and five populations in the lower Fraser Valley.

Lupinus rivularis is distinguished by its absence of wood, banners that are glabrous abaxially, ciliate keels, glabrous leaf surfaces, and violet flowers. It grades into blue-flowered L. arboreus but blooms earlier (late winter, spring) and is not sweet-smelling. L. L. Phillips (1955) considered L. rivularis as synonymous with L. albicaulis.

Lupinus rivularis is widely planted for erosion control in western Oregon; it is of conservation concern in Canada.

Selected References

None.

Lower Taxa