About Lupinus arboreus Sims
Lupinus arboreus Sims, commonly known as tree lupine, is an evergreen shrub. In sheltered locations it can reach 2 meters (7 feet) tall, but more typically grows between 1 and 1.5 meters (3 to 5 feet) tall. It can tolerate temperatures as low as −12 °C, and has a maximum lifespan of seven years.
Its leaves are palmate, ranging from green to gray-green, with 5 to 12 leaflets per leaf. Each leaflet measures 2 to 6 centimeters (0.79 to 2.36 inches) long, and is often sparsely covered with fine silky hairs. In spring, it produces many 30-centimeter (12-inch) long racemes of fragrant, soft yellow, pea-like flowers. While both yellow and lilac-to-purple flowering forms exist, the yellow form is more common across most of the species' range, except in the northern part of its range.
This shrub is indigenous to California, the United States, where it is widely distributed in coastal sage scrub and sand dune habitats. There is some uncertainty around its exact native range because it has been widely introduced across the state; it is currently thought to be native to the region from Point Reyes National Seashore south to San Luis Obispo County.
The yellow-flowering form of Lupinus arboreus is widely cultivated as an ornamental plant. It is used for its attractive blooms in traditional gardens, native plant gardens, and wildlife gardens. It is also employed to stabilize drifting sand dunes. It often grows in cracks on vertical stone walls, where sharp drainage suits it, and can also be grown in pots on balconies or patios. This form has been awarded the Royal Horticultural Society's Award of Garden Merit.
