Wild lupin, Lupinus perennis, is an herbaceous perennial that reaches 8 to 30 inches tall. Several stems grow from a single creeping root and bear palmate leaves divided into seven to 11 leaflets. Wild lupin blossoms from May through June, producing blue and white pealike flowers clustered on a tall spikes. Hairy, oblong seed pods appear after the blooms fade. Lupin flourishes in woods, prairies and gardens. It grows slowly into a full, dense cover. This perennial enjoys the cool weather of spring and even tolerates frosts.
Choose a planting area located in full to partial sun. Lupin tolerates dry, sandy soil, to moist, clay soil, as long as it is well-drained. Remove the weeds, grass and brush from your planting area. Keep the site free of weeds and turf, since lupin does not grow well with competition.
Break up the soil with a shovel to a depth of 24 inches. Turn the soil over and break up dirt clumps with the edge of a garden hoe. Wild lupin develops a large, deep taproot before it produces blossoms, so it needs lots of depth to thrive. Rake the soil smooth and even.
Plant wild lupin seeds in April. Place them 1/2-inch deep in the planting area. Cover them lightly with soil.
Sprinkle the planting area with water until the soil is wet. Keep the soil moist while waiting for the lupin seeds to sprout. After growth has started, water your lupins only when there have been long periods without rain.
Cut fading lupin blossoms with a pair of shears to promote the growth of more stems and prolong the flowering season. Stop deadheading when you are ready to produce lupin seeds. Let the seed pods dry on the plant before harvesting the seeds.
Wild lupin plants are part of the legume family, which fixes nitrogen in the soil. This increases the nutrients and fertility of the soil.
All parts of the wild lupin plants are toxic, especially the seedpods. Ingestion of plant parts can cause breathing problems, behavioural changes, trembling, coma and even death. Grazing animals are susceptible to lupin poisoning. Lupin is known to produce birth defects in livestock.