Silvery lupine, Lupinus argenteus, in the meadow beneath the flatirons

Photo by Jeff Mitton

The flowers of lupines are arranged in racemes

Photo by Jeff Mitton

Indian paintbrush, genus Castilleja, are hemiparasitic on lupines. They extract the alkaloid compounds from lupines, and use them to repel herbivores

Photo by Jeff Mitton

Many plants do not bristle with spines or thorns, but are adequately defended by a bouquet of nasty chemicals. Lupines, our native wildflowers, illustrate the full range of the consequences of chemical diversity. Depending on the circumstances, lupines provide wholesome food, toxic or deadly compounds, and valuable medicines.

Lupines are in the genus Lupinus ; this name is derived from the Latin word “lupus” (meaning wolf) perhaps because a legend asserts that these plants destroy the soul. I suspect that this legend has its roots in the human symptoms of alkaloid poisoning, which include dizziness, incoordination, labored breathing, convulsions, coma, and death by asphyxiation. This legend would have been nurtured by recurrent poisonings through the years, resulting from eating the wrong species. Another explanation for naming lupines after wolves is that both lupines and wolves are sheep killers.

Lupines are perennial herbs most easily recognized by their racemes, or long, conical flower heads (see the web site photos). The flowers can be blue, purple, red, white, or multicolored, depending on the species. The most common local lupine is Lupinus argenteus, which grows three feet tall with numerous racemes profuse with blue and purple flowers. Leaves usually have 5 to 7 elongate, rounded leaflets arranged in the shape of a fan.

Lupines are in the pea family, and like other legumes, they form a symbiosis with bacteria that enables them to fix nitrogen. Nitrogen fixers are often nutritious for man and beast. The species chosen for cultivation typically have low levels of alkaloids, and if the seed pods have any alkaloids at all, alkaloids can be removed by leaching or steaming. The Mediterranean white lupine, L. albus, has been cultivated in Europe for several thousand years to provide food for farmers and forage for cattle. Polish plant breeders have developed Amulet, a new variety with 48% protein (higher than soybean) and only 4% fat. The pearl lupine, L. mutabilis has been cultivated for thousands of years in the Andean highlands in South America.

Alkaloids defend lupines by making them distasteful and toxic. The concentrations and forms of alkaloids are highly variable among species, and among localities within a species. In some areas, such as the Channeled Scablands of central Washington, the lupines are so common and toxic that they chronically poison sheep and cows. The alkaloid most threatening to livestock is lupinin. Sheep are most susceptible, and numerous sheep die after browsing lupines. Adult cows are rarely killed, but lupinin anesthetizes embryos, and the lack of fetal activity causes a birth defect colloquially called “crooked calf.” Animals suffering this syndrome have twisted necks and backs and malformed leg joints; crooked calves cannot forage for food, and must be euthanized. Ranchers in Europe, North America, Australia and New Zealand dread the colorful lupines in their pastures.

Toxic chemicals can also serve as medicines. The alkaloid lupinin is now being investigated as a preventative for the plaques in the brain that accompany (or cause) Alzheimer’s disease. The Navajo made a paste from lupine seeds to treat skin ulcers and sores.

Toxic, defensive chemicals can be so valuable that they are worth stealing. Lupines are commonly sympatric with several species of Indian paintbrush (see web photos), which are also native wildflowers. Species of Indian paintbrush, genus Castilleja, are hemiparasites. Indian paintbrush graft their roots onto the roots of nearby plants, such as sagebrush or lupine, and then siphon off water, nutrients, and defensive compounds. Careful studies in experimental gardens demonstrate that the hemiparasites parasitizing toxic lupines suffer less herbivory than those parsitizing edible lupines. Indian paintbrush extract alkaloids, and use them to dissuade hungry herbivores.