Covering the slopes and subalpine meadows of western North America, the silver lupine (Lupinus argenteus), exhibits a beautiful display of lavender/blue in spring and early summer. A member of the pea family, lupine flowers bloom on spikes rising 8 to 24 inches above bright green leaves, which are displayed in rosettes of 5 to 9 narrow leaflets branching from the stem main. The flowers are usually purple to light blue and vary in intensity depending on soil composition, light and humidity. The characteristic “banner” at the top of the sweet pea-like flower is white in the center, giving a silvery impression to the overall color.
When it comes to soil, Lupine is quite easy to please. It prefers gravelly textured, relatively dry to moderately moist soils in mostly sunny locations, although it does well in partial shade. A hardy perennial, lupine propagates by seed and is easily controlled in gardens by removing the pods. Deep roots make lupine difficult to transplant.
Easy-to-grow lupine is often included in mixed wildflower seed packets, both for its beauty as a garden flower and for its ability to attract pollinators, including bees, hoverflies, hummingbirds and the butterflies. First-generation worker bumblebees harvest bright red-orange lupine pollen.
Like other members of the pea family, lupine is an important nitrogen-fixing plant, valuable in regeneration projects. A beneficial bacterium can “infect” the roots by forming nodules. The bacterium converts atmospheric nitrogen into nitrogen fertilizer that the plant can use. The plant provides a source of sweet food for bacteria. This symbiotic relationship allows lupine to enrich depleted soils by making them suitable for other species.
The pods and seeds of lupine contain alkaloids which (even after drying) can be toxic to humans and animals if ingested in sufficient quantity. A benefit to the home gardener, this toxicity means lupine is rarely attractive to wildlife as a forage plant. Silver Lupine is a nice addition to the home garden, but perhaps not if your garden borders your neighbor’s pasture.
Enjoy Lupine in the North Idaho Native Plant Arboretum, 611 S Ella Ave. Silver Lupine can be found on page 166 of the KNPS publication, Landscaping with Native Plants in the Idaho Panhandle, available at local bookstores and the Bonner County History Museum.
Native Plant Notes are created by the Kinnikinnick Native Plant Society. To learn more about KNPS and the North Idaho Native Plant Arboretum, visit www.nativeplantsociety.org.