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Idaho Mountain Wildflowers

The Pea Family: Fabaceae (page 2 of 4)

Astragalus species, the milk vetches

There are at least 100 species and many more varieties of Astragalus native to the Northwest. To say that classifying them can be difficult is an understatement. We believe, but are not certain, that the following plant identifications are correct. Many milk vetches are poisonous to livestock and are despised by cattlemen, explaining such descriptive common names as loco-weed, and poison vetch, nevertheless, their attractive flowers do serve to brighten our mountain landscapes.

Pursh's milk vetch, Astragalus purshii var. concinnus, is an attractive, low plant that grows to mid-elevations in our mountains. As with many members of the family there are several varietal forms and their flowers vary in color, ranging from yellow, through white, to purple tinged. The species name honors Frederick Pursh (1774-1820), who identified many new species collected by Lewis and Clark and by other explorers and plant-hunters. David Douglas (1798-1834) suggested that this species be named to honor Pursh (although Pursh apparently had never seen the plant.) The derivation of astragalus is interesting. The dried pods of some species ("rattle-boxes") suggest the sound of dice shaken 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 in turn from the Greek astragalos = ankle. The varietal form shown here is var. concinnus, a Latin word that, fittingly, means "neat," or "elegant."

The Canadian milkvetch, Astragalus canadensis var. mortonii. The Canadian milkvetch is is a common plant that grows at all elevations, well up into the mountains (7000' in Central Idaho). It is an widespread species found throughout North America, although our varietal form, var. mortonii, is found only in the northwestern states and British Columbia. The plants usually grow in circumscribed patches identifiable by their unusually tall (for a milkvetch) upright stems, by congested clusters of pea-like flowers and, in our variety by a calyx covered with black and white hairs. It is not an unattractive plant, one that might be suitable for an ornamental garden

The Indian milkvetch, Astragalus aboriginum, grows on windswept rocky soil. There is some variation from place to place, but typically the banner is erect, the flowers are whitish with purple markings on the keel, and the ends of the wings are notched. The leaves have 7-15 closely ranked leaflets. (Photographed on the boundary between the White Cloud and Boulder Ranges.)

Astragalus platytropis, Broad-keeled milk vetch. This plant, photographed on Railroad Ridge in the White Clouds, stands only about 4" high, with stems arising from an exposed root crown. Bright purple flowers stand out sharply against the drab background of alpine tundra. The banner is not erect and the keel is broad and flat (platytropis="flat-keel"). Each leaf has 13-21 leaflets in close array.

Astragalus vexilliflexus var. nubilus, Bent-flowered milk vetch. A tiny-leaved, densely matted, small-flowered plant, the bent-flowered milk vetch stands only an inch or so high. Although the species vexilliflexus is found in the Rockies from Alberta to Wyoming, this varietal form, nubilis, 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 (or banner)" and the varietal name, nubilus, means grayish-blue.

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Pursh's milk vetch, Astragalus purshii var. *concinnus, is an attractive, low plant that grows to mid-elevations in our mountains. As with many members of the family there are several varietal forms and their flowers vary in color, ranging from yellow, through white, to purple tinged. The species name honors Frederick Pursh (1774-1820), who identified many new species collected by Lewis and Clark and by other explorers and plant-hunters. David Douglas (1798-1834) suggested that this species be named to honor Pursh (although Pursh apparently had never seen the plant.) The derivation of astragalus* is interesting. The dried pods of some species ("rattle-boxes") suggest the sound of dice shaken 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 in turn from the Greek astragalos = ankle. The varietal form shown here is var. concinnus, a Latin word that, fittingly, means "neat," or "elegant."
The Canadian milkvetch, Astragalus canadensis var. mortonii. The Canadian milkvetch is is a common plant that grows at all elevations, well up into the mountains (7000' in Central Idaho). It is an widespread species found throughout North America, although our varietal form, var. mortonii, is found only in the northwestern states and British Columbia. The plants usually grow in circumscribed patches identifiable by their unusually tall (for a milkvetch) upright stems, by congested clusters of pea-like flowers and, in our variety by a calyx covered with black and white hairs. It is not an unattractive plant, one that might be suitable for an ornamental garden

The Indian milkvetch, Astragalus aboriginum, grows on windswept rocky soil. There is some variation from place to place, but typically the banner is erect, the flowers are whitish with purple markings on the keel, and the ends of the wings are notched. The leaves have 7-15 closely ranked leaflets. (Photographed on the boundary between the White Cloud and Boulder Ranges.)
Astragalus platytropis, Broad-keeled milk vetch. This plant, photographed on Railroad Ridge in the White Clouds, stands only about 4" high, with stems arising from an exposed root crown. Bright purple flowers stand out sharply against the drab background of alpine tundra. The banner is not erect and the keel is broad and flat (platytropis="flat-keel"). Each leaf has 13-21 leaflets in close array.
Astragalus vexilliflexus var. nubilus, Bent-flowered milk vetch. A tiny-leaved, densely matted, small-flowered plant, the bent-flowered milk vetch stands only an inch or so high. Although the species vexilliflexus is found in the Rockies from Alberta to Wyoming, this varietal form, nubilis, 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 (or banner)" and the varietal name, nubilus, means grayish-blue.