Lupinus polyphyllus (large-leaved lupine, big-leaved lupine, many-leaved lupine or, primarily in cultivation, garden lupin) is a species of lupine (lupin) native to western North America from southern Alaska and British Columbia east to Quebec, and western Wyoming, and south to Utah and California. It commonly grows along streams and creeks, preferring moist habitats.
It is a perennial herbaceous plant with stout stems growing to 1.5 metres (4.9 ft) tall. The leaves are palmately compound with (5-) 9-17 leaflets 3–15 centimetres (1.2–5.9 in) long. The flowers are produced on a tall spike, each flower 1–1.5 centimetres (0.39–0.59 in) long, most commonly blue to purple in wild plants. The flowers are mostly visited by bumblebees. The polyphyllus variety in particular make up a great number of the hybrids which are generally grown as garden lupines, they can vary dramatically in colours. The majority of lupines do not thrive in rich heavy soils, and often only live for a matter of years if grown in such places, crown contact with manure or rich organic matter encourages rotting.
There are five varieties:
- Lupinus polyphyllus var. burkei – Interior northwestern United States
- Lupinus polyphyllus var. humicola – Interior western North America
- Lupinus polyphyllus var. pallidipes – Western Oregon and Washington (Willamette Valley)
- Lupinus polyphyllus var. polyphyllus – Coastal western North America
- Lupinus polyphyllus var. prunophilus – Interior western North America