Lupinus polyphyllus aka Garden Lupin

Lupinus polyphyllus, or bigleaf lupin, belongs to the pea family, Fabaceae. This perennial comes from North America and grows in temperate climates. Kew lists western Canada and the western United States within its native range. Its range also includes eastern Canada and north-central and northeastern United States. PFAF records it in wetlands, from sea level into mountain habitats. It is not native to Britain or Ireland.

The plant forms an upright clump with a leafy mound. In gardens, it reaches 3.3–4.9 feet (1–1.5 metres) tall. Its spread reaches 1.6–3.3 feet (0.5–1 metre). Plants take two to five years to reach full size. The large, mid-green leaves grow on long stalks. Each leaf divides into narrow leaflets. The foliage dies back rather than staying green through winter. Tall plants may need stakes to keep their stems upright.

Summer brings tall spikes of pea-like flowers above the leaves. The blooms may be blue, purple or reddish. Each flower spike can reach about 1.3 feet (0.4 metres) long. Removing spent flower spikes can prompt another flush of bloom. PFAF reports that the flowers draw bees and butterflies. The blooms suit both fresh-cut and dried flower use. The bold leaves also give the plant value outside flowering time.

Grow this lupin in full sun or light shade. RHS favours light, slightly acid soil that drains well. Its soil listing also includes neutral soil, clay, loam and sand. Moist but well-drained ground suits it, though RHS also records drought resistance. RHS rates its cold hardiness as H6. PFAF gives a USDA range of zones 5–9. Sow seed in early to mid-spring to raise new plants. Basal stem cuttings offer another method in mid- to late spring.

This species suits beds, borders and informal cottage gardens. PFAF also lists containers, mass planting and woodland gardens as uses. As a nitrogen fixer, it can help improve soil fertility. Other listed uses include cover cropping and erosion control. Watch for lupin aphids, slugs and snails. Lupin anthracnose, powdery mildew and viruses can also affect plants. RHS warns that eating it can harm people and pets. It advises gloves and other protection when handling the plant. PFAF records raw or cooked root use, but also warns of toxic seed alkaloids. Those reports do not establish that this plant is safe food.