The skyblue lupine (Lupinus diffusus Nuttall) is native to dry, nutrient-poor uplands—sandhills, scrubs, and flatwoods—of the southeastern U.S. The plants have a silvery appearance and a silky 'feel' due to long trichomes (plant hairs). In Florida, the skyblue lupine blooms from midwinter to early spring.

Depending upon the authority, there are two hundred to five hundred species of lupines widely distributed across Asia, Europe, and North and South America. There are 156 species in the continental U.S. alone. Lupines are members of the "butterfly-flowered" subfamily, Papilionoideae, of the Fabaceae, the legumes. The papilionaceous corolla consists of an upright standard petal, two wing petals, and a keel petal that protects the stigma, stamens, and nectary. Bees are the primary pollinator since they are capable of manipulating past the keel petal. (Guide to Flowering Plant Families, Wendy B. Zomlefer, University of North Carolina Press, Chapel Hill, 1994)

Some lupines are grown as ornamentals; others are agricultural—cover crops to enrich the soil, animal forage, and human consumption. But most of the species are simply wild either due to poor germination rates, difficult cultivation, or containing toxic lectins or alkaloids. The skyblue lupine is obviously unpalatable and/or toxic as it shows no signs of grazing in an overgrazed pasture.

Like many other legumes, lupines have a symbiotic relationship with nitrogen-fixing bacteria. The bacteria absorb atmospheric nitrogen (N₂) and convert it to ammonia (NH₃). The ammonia is used as a building block for amino acids and proteins. Lupines grow on impoverished soils because the fixation of atmospheric nitrogen means they can thrive without nitrogen in the soil. Any excess ammonia is available to other plants. (See Weird Plants, July 10, 2003)

But in the past, lupines were not believed beneficial. The generic name dates back to the Romans: lupus, "wolf", lupinus, "of wolves". Lupines were thought to create the poor soils where they grew thereby killing other plants.