Idaho Mountain Wildflowers

Home | Next | Previous | Index | Purchase book

The Pea Family: Fabaceae

The older scientific name for the pea family, Leguminosae, is one of several family names that don’t end in “-aceae”, so many botanists prefer Fabaceae (from the Latin word “faba,” for “bean”). Either name is correct. The family is large and taxonomically difficult even for botanists. It is made up of more than 630 genera and approximately 18,000 species including herbs, vines, shrubs and trees. It is second only to the grasses (Poaceae) in economic importance. The flowers of many of the family’s plants are made up of five petals that include a large upper petal, or “banner,” two smaller lateral ones (“wings”), and the two lowest ones joined together to form a “keel.” The flowers are “papilionaceous,” a word derived from papilion, the Latin word for “butterfly.” The fruit is a pod that splits open along two seams. Leaves are compound: either pinnate (like a feather) or palmate (leaflets arise from a central point, like fingers from the palm). The family includes beans, peas, lentils, peanuts, clover, alfalfa, etc., plants important not only for their food value to man and domestic animals, but also for their ability to fix soil nitrogen. About twenty-five genera, including both native and introduced species, grow in the Northwest; many are found in our mountains. Although some have edible fruit, others are poisonous, so it is best to regard all wild leguminaceous plants as inedible.

Silver lupine, Lupinus argenteus Pursh var. depressus (Rydb.) C. L. Hitchc. (left, right). Although the silver (or silvery) lupine is found in most states west of the Mississippi River, the variety shown here is restricted to the mountains of Idaho, Montana and Wyoming. It seldom grows more than a foot high and is quite at home at high elevations where alpine meadows are often covered with its bright flowers. It may be identified by this growth preference and by its crowded clusters of purple to blue flowers. Both flowering and fruiting plants, the latter with their typical pea-like pods, are shown on the right Recently, some have classified var. depressus as its own species, Lupinus depressus (the species name means “low”). The Lewis and Clark expedition returned a specimen of Lupinus argenteus var. argenteus, collected in Montana, on July 7, 1806.

Silky lupine, Lupinus sericeus Pursh (left, right). The silky lupine is usually blue, but ranges from off-white to the intense blue shown here. It is a foothills plant, growing no higher than the montane zone. It can be distinguished from Lupinus argenteus by its rounded leaflets, and a banner (the large upper petal) that is usually hairy on the back with a white center. Meriwether Lewis collected a specimen on the Clearwater River in today’s north-central Idaho on June 5, 1806.

It can be difficult to distinguish between Lupinus argenteus and Lupinus sericeus. The flower clusters of the latter tend to be looser and are lower, extending well into the plant’s leaves; its indvidual flowers tend to be smaller. The banners are often lighter or partially white, its calyces have a hump on the dorsal surface, and the leaflets tend to be less pointed at the ends. Finally, as noted, Lupinus argenteus grows to higher elevations.

Longspur lupine, Lupinus arbustus Douglas ex Lindl. var. calcaratus (Kellogg) S. L. Welsh (left & above). This plant, formerly classified as Lupinus calcaratus has recently been reclassified; (arbustus means “small tree, or shrub” and calcaratus means “spurred” for a bump-like projection that extends backward from the top of the calyx). It is common in the Rocky Mountains and west to the coast, often growing in amazing profusion on sagebrush slopes as high as the subalpine zone. The color of the flowers varies considerably, from light purple to yellow—those shown here are typical.

Stemless dwarf lupine, Lupinus lepidus Douglas ex Lindl. var. utahensis (S. Watson) C. L. Hitchc. (right). This little lupine grows in the grass of montane meadows. Its flowers have short stems and the leaves, stems and base of the flowers are covered with long hairs giving the plant a furry, grayish appearance that serves to identify it.

Milk-vetches, Astragalus species: Astragalus is a large genus with approximately 1,750 species worldwide; many are found in our mountains—a few representative species are shown here. The genus is characterized by pea-like, odd-pinnate leaves (“odd-pinnate” implies opposing leaflets in a feather like arrangement with a single leaflet at the end), and papilionaceous flowers. The plants typically are low with colorful clusters of white, yellow, or pink-to-purple flowers. Because there are many plants in the genus Astragalus and because many species are alike, milk vetches can be difficult to identify, especially before pods form. Dried seed-containing pods of some species rattle when shaken, suggesting the sound of dice in a cup. In ancient times dice were made from the ankle bones of animals (sheep and goats especially). These were called “astragals,” a word derived from the Greek word astragalos for ankle, hence Astragalus for the plant.

Field, or purple, milk-vetch, Astragalus agrestis S. Watson (left). The field  milk-vetch is a common meadow plant that may grow as high as treeline and is found in all but the southern-most western states and as far east as the Mississippi River in the United States and Manitoba in Canada.  Clustered purple flowers are borne at the end of a separate stem. 12 to 23 leaflets are long-oval in shape; the pod is rather short and said to be 3-cornered. The species name, agrestis, means "rustic."

Alpine milk-vetch, Astagalus alpinus Douglas ex G. Don (right). Despite its name, the alpine milk-vetch grows also at lower altitudes. Its distribution in the States is much the same as the rather similar purple milk-vetch (left), although it is a circumboreal plant that grows in all of the Canadian provinces, Greenland and Eurasia. Both plants are commonly encountered in Idaho. The alpine-milk-vetch's leaflets are smaller and rounder, and its pod is long and darkly pigmented than those of the purple milk-vetch.

Pursh’s milk-vetch, Astragalus purshii Douglas ex Hook. (left). Astragalus purshii, grows as high as the montane zone. There are many varietal forms (the one shown here is var. concinnus). All have a prominent calyx and their flowers range in color from white through yellow to a purple-tinged pink, as in this illustration. The species name honors Frederick Pursh (1774-1820), the botanist who identified and published descriptions of many of the plants that Lewis and Clark collected.

Canadian milk-vetch, Astragalus canadensis L. var. mortonii (Nutt.) S. Watson (right). The Canadian milk-vetch grows from sea level to as high as the montane zone in our mountains. The variety shown here is found only in Idaho, Washington, Montana and British Columbia. The plants spread by rhizomes to form circumscribed patches. They have upright stems, clusters of yellowish-white pea-like flowers and, in our variety, a calyx covered with black and white hairs. This variety, var.  mortonii, was gathered by Nathaniel Wyeth in 1833 and named to honor Philadelphia naturalist Samuel George Morton (1799-1851). Another variety, var brevidens (Gandog.) Barneby has much the same appearence except that it is a lower, more sprawling plant found often in moist situations. It's distribution is less restricted for it grows also in California, Nevada, Utah, Wyoming and Colorado.

Indian milk-vetch, Astragalus australis (L.) Lam. var. glabriusculus (Hook.) Isley (left). Indian milk-vetch (formerly Astragalus aboriginorum) grows to treeline and above, on exposed wind-swept, rocky soil. The plants vary from place to place, but typically the banner is erect, the flowers are whitish and often have purple markings on the keel and the ends of the wings are slightly notched. The leaves have seven to fifteen closely ranked leaflets. Its roots are said to be edible.

Bent-flowered milk-vetch, Astragalus vexilliflexus Sheldon var. nubilus Barneby (left). The bent-flowered milk-vetch is a tiny-leaved, small-flowered, densely matted plant that stands only an inch or so high. Although the species is found in the Rocky Mountains from Alberta to Wyoming, the varietyshown here, occurs only in central Idaho’s Custer County. (This plant was photographed well above treeline on Mt. Borah in the Lost River Range.) The species name, vexilliflexus, means, roughly “flexed standard,” referring to the banner. The varietal name, nubilus, means grayish-blue, for the leaves.

Home | Next | Previous | Index | Purchase book