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BIdaho Mountain Wildflowers

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). 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. (Recently, some have classified this plant as its own species, Lupinus depressus (the species name means “low”).The Lewis and Clark expedition returned a specimen of Lupinus argenteus), collected in Montana, on July 7, 1806.
Silky lupine, Lupinus sericeus Pursh (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 sericeus and Lupinus argenteus. The flower clusters of the former 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. Both plants are variably hairy; Lupinus sericeus is usually more so, and its calyx has a hump on the dorsal surface.

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 great 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 white, yellow, or pink-to-purple flowers. Many are difficult to identify. 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.
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 the northwestern states 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. The variety, mortonii, was gathered by Nathaniel Wyeth in 1833 and named to honor Philadelphia naturalist Samuel George Morton (1799-1851).

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.

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	*Silver lupine, Lupinus argenteus* Pursh var. depressus (Rydb.) C. L. Hitchc*. (left). 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. (Recently, some have classified this plant as its own species, Lupinus depressus* (the species name means “low”).The Lewis and Clark expedition returned a specimen of Lupinus argenteus), collected in Montana, on July 7, 1806. *Silky lupine, Lupinus sericeus* Pursh** (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 sericeus and Lupinus argenteus. The flower clusters of the former 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. Both plants are variably hairy; Lupinus sericeus is usually more so, and its calyx has a hump on the dorsal surface.
	*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 great 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 white, yellow, or pink-to-purple flowers. Many are difficult to identify. 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. *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 the northwestern states 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. The variety, mortonii, was gathered by Nathaniel Wyeth in 1833 and named to honor Philadelphia naturalist Samuel George Morton (1799-1851).
	*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.