This is the common lupine at lower and middle elevations in the Boise Front, beloved for its colorful displays and heady fragrance.  It can be told apart from other locally occurring species, which tend to bloom later and/or at higher elevations, by the wild variation in flower color, ranging from nearly white to yellow to violet, not only between plants but even in the same inflorescence. The relatively longer spur (i.e., bump at the back of the flower) is another diagnostic character.

Although longspur lupine is the “official” common name, I like to call the populations in the Boise foothills the “polychrome lupine”, since local flower color varies even more than is the norm for this species.  Some of the color difference, especially on the same plant, is how the plant communicates with its pollinators (mostly bees); the flowers change color when they are ready for pollinating, and then change again to a different color when the have already been pollinated, or are at least past peak.

Bernice Bjornson‘s comments on this species in 1946:

“The most common lupine here is Lupinus laxiflorus var. calcaratus [a name used in many earlier references for this species]. Its flowers differ a good deal in color, ranging from blue to pale yellow or white. We have seen meadows covered with clumps of this species where the usual color was lavender in the oldest flowers of a raceme shading to yellow in the youngest. The flowers are spurred and have a fragrance which can be appreciated outdoors, but which is too strong when confined in a room. Perhaps you have already learned this through experience.”  [NOTE:  Collecting wildflowers is no longer encouraged]

Her comments on pollination in lupines, and many other members of the pea family:

“The lupines have a peculiar device for placing pollen on the visiting bee that he may carry it to the next flower and thus effect cross-pollination. When the bee alights to gather nectar his weight causes the lip to bend down and a piston then pushes out a bit of pollen. To see how it works, suppose you take hold of the wings of a flower and pull them downward. Note how the pollen is pushed out.”

You can also observe this intriguing pollination mechanism by inserting a cotton swab into the flower, imitating a bee forcing its way into the flower (and nectar reward).  Note how the style (female) and anthers (male) are triggered into jutting out, smearing pollen on the surrogate bee’s belly and/or picking up pollen from a previously visited flower.

Bjornson’s comments on the name of the genus:

“The generic name, Lupinus, comes from the Latin word meaning wolf.  No connection between lupines and wolves can be seen unless, as has been suggested, it was once thought the plants robbed the soil of its fertility.  Lupines, however, like the clovers, alfalfa, beans, peas, and other members of the pea family, help to enrich the soil by harboring in their roots certain bacteria.  These bacteria are able to take the nitrogen of the air and combine it with other substances to make nitrates.  Nitrates are soluble and can be used by green plants in building proteins and protoplasm.  The bacteria in the roots of legumes make more nitrates than they or the legumes can use; hence, at the death of the roots some becomes available for other plants.  This addition of nitrates is what is meant when we say legumes enrich the soil in which they grow.