[Milkvetch: The Genus Astragalus East of the Cascade Mountains of Oregon and Washington]

Idaho Milkvetch, Idaho Milk-vetch, Stiff Milkvetch, Stiff Milk-vetch

Astragalus conjunctus var. rickardii

Synonym: Astragalus reventus var. rickardii

Idaho Milkvetch, Idaho Milk-vetch, Stiff Milkvetch, Stiff Milk-vetch: Astragalus conjunctus var. rickardii (Synonym: Astragalus reventus var. rickardii)

The photo above shows a close-up side view of the corolla and calyx of Idaho milk-vetch as seen from slopes along OR Highway 219 east of the Deschutes River in north-central Oregon...........April 19, 2007. Note the long, narrow wings and the purplish tip of the keel and erect banner. Note also the numerous hairs on the surface of the calyx. This is probably an example of Astragalus conjunctus var. rickardii as evidenced by the hairy pods seen below. Note that the calyx tube is twice as long as wide .
Characteristics:

Also known as stiff milk-vetch, Idaho milk-vetch is an upright, many-stemmed perennial arising to a height of 40 cm. The stems and leaves are sparsely haired with minute, straight, stiff, sharp and appressed hairs. The leaves are numerous, from 7-30 cm long, with 13-31 leaflets which are linear to oblong-oblanceolate in shape, and 3-25 mm long and 1-4 mm wide (See photo below.). The margins of the leaflets are also rolled upwards (See photo below.) The leaves are held stiffly erect, helping give it one of its names, "stiff" milk-vetch.

The racemes are held equal to or slightly exceeding the leaves. They contain 7-35 flowers which may droop slightly or also be held erect or spreading. Individual flowers are creamy or slightly yellow-tinged in color and 13-23 mm long. The tips of the petals are often tipped with bluish-purple and the upturned tip of the keel is frequently tipped with purple. The banner is often well reflexed upward, and the wing petals are about 2-4 mm longer than the keel. The calyx is 6-15 mm long (varying from less than the width long to twice the thickness), whitish to blackish with appressed hairs. The calyx teeth are narrowly triangular and measure from 2-5 mm long. Bloom time is typically April through June.

The pods are covered with numerous hairs, green at first, and 3-6 mm thick and up to 30 mm long. The pod may be straight to slightly arched and is held erect.

Similar Species:

Idaho Milk-vetch: Astragalus conjunctus var. conjunctus - Calyx cylindrical, 6-15 mm long, about 2 times as long as thick. Calyx teeth 1.5-3 mm long. Corolla white or with purplish tip to keel and banner. Leaflets 13-31. Pod glabrous. Found from Wasco County, northcentral Oregon east to the Blue Mts. and south to the the Steens Mt. and east to southwestern Idaho.

Hood River Milk-vetch: Astragalus hoodianus - Calyx bell-shaped, 11-15 mm long, about 1.5 times as long as thick. Calyx teeth 4.5-7.5 mm long. Leaflets 17-37. Pod pubescent. Found near the Columbia River Gorge in Wasco and Hood River Counties in Oregon and Klickitat County in Washington.

Yakima Milk-vetch: Astragalus reventiformis - Calyx bell-shaped, 8-12 mm long, about 1.5 times as long as thick. Calyx teeth 2.5-5 mm long. Leaflets 17-37. Pod pubescent. Found from Kittitas County in Washington near Ellensburg south to Klickitat County, Washington and south into Sherman County of Oregon.

Blue Mt. Milk-vetch: Astragalus reventus - Leaflets 23-41. Pod glabrous. Found in the Blue Mts. of northeastern Oregon near the headwaters of the Umatilla and Grande Ronde Rivers into southeastern Washington.

Sheldon's Milk-vetch: Astragalus sheldonii - Leaflets 23-41. Pod usually pubescent. Found from southern Asotin County in southeastern Washington south into Wallowa County, northeastern Oregon and into Lewis and Nez Perce Counties in Idaho.

Habitat:

Idaho milk-vetch is found on dry rocky slopes, scablands, and hilltops throughout the sagebrush desert. It typically is found above 2000 feet.

Range:

Idaho milk-vetch is primarily found east of the Cascade Mts. in north-central Oregon to the Blue Mts, and then southward a long the Malheur River to the Steens Mt. into southwest Idaho.

Close-up sideview of the pod of Idaho Milkvetch, Idaho Milk-vetch, Stiff Milkvetch, Stiff Milk-vetch: Astragalus conjunctus var. rickardii (Synonym: Astragalus reventus var. rickardii) - Ventral view of the broad pod of Idaho Milkvetch, Idaho Milk-vetch, Stiff Milkvetch, Stiff Milk-vetch: Astragalus conjunctus var. rickardii (Synonym: Astragalus reventus var. rickardii)

The photo above shows two views of the pod of Idaho milk-vetch. Photographed from slopes along OR Highway 219 east of the Deschutes River in north-central Oregon.........April 19, 2007. Note the minute hairs on the surface of the pod. The pods of variety conjunctus should be glabrous, so the plants at this site are most likely those of Astragalus conjunctus var. rickardii).

Idaho Milkvetch, Idaho Milk-vetch, Stiff Milkvetch, Stiff Milk-vetch: Astragalus conjunctus var. rickardii (Synonym: Astragalus reventus var. rickardii) - Habitat of Idaho Milkvetch, Idaho Milk-vetch, Stiff Milkvetch, Stiff Milk-vetch: Astragalus conjunctus var. rickardii (Synonym: Astragalus reventus var. rickardii)

Pods of Idaho Milkvetch, Idaho Milk-vetch, Stiff Milkvetch, Stiff Milk-vetch: Astragalus conjunctus var. rickardii (Synonym: Astragalus reventus var. rickardii) - Sideview of a maturing pod of Idaho Milkvetch, Idaho Milk-vetch, Stiff Milkvetch, Stiff Milk-vetch: Astragalus conjunctus var. rickardii (Synonym: Astragalus reventus var. rickardii) - Inflorescence of Idaho Milkvetch, Idaho Milk-vetch, Stiff Milkvetch, Stiff Milk-vetch: Astragalus conjunctus var. rickardii (Synonym: Astragalus reventus var. rickardii)

Flower of Idaho Milkvetch, Idaho Milk-vetch, Stiff Milkvetch, Stiff Milk-vetch: Astragalus conjunctus var. rickardii (Synonym: Astragalus reventus var. rickardii) - Flower of Idaho Milkvetch, Idaho Milk-vetch, Stiff Milkvetch, Stiff Milk-vetch: Astragalus conjunctus var. rickardii (Synonym: Astragalus reventus var. rickardii) - Inflorescence of Idaho Milkvetch, Idaho Milk-vetch, Stiff Milkvetch, Stiff Milk-vetch: Astragalus conjunctus var. rickardii (Synonym: Astragalus reventus var. rickardii)

Pods of Idaho Milkvetch, Idaho Milk-vetch, Stiff Milkvetch, Stiff Milk-vetch: Astragalus conjunctus var. rickardii (Synonym: Astragalus reventus var. rickardii) - Flowers of Idaho Milkvetch, Idaho Milk-vetch, Stiff Milkvetch, Stiff Milk-vetch: Astragalus conjunctus var. rickardii (Synonym: Astragalus reventus var. rickardii)

Idaho milkvetch as seen on north-facing, grassland slopes above the John Day River at Cottonwood Canyon State Park..........April 9, 2016. Note that the calyx tube is twice as long as wide, the banner is nearly erect, and the purple tip to the keel. The developing fruits have numerous, mostly appressed hairs covering their surfaces.

Fruits of Idaho Milkvetch, Idaho Milk-vetch, Stiff Milkvetch, Stiff Milk-vetch: Astragalus conjunctus var. rickardii (Synonym: Astragalus reventus var. rickardii) - Habitat of Idaho Milkvetch, Idaho Milk-vetch, Stiff Milkvetch, Stiff Milk-vetch: Astragalus conjunctus var. rickardii (Synonym: Astragalus reventus var. rickardii) - Habitat of Idaho Milkvetch, Idaho Milk-vetch, Stiff Milkvetch, Stiff Milk-vetch: Astragalus conjunctus var. rickardii (Synonym: Astragalus reventus var. rickardii) - Habitat of Idaho Milkvetch, Idaho Milk-vetch, Stiff Milkvetch, Stiff Milk-vetch: Astragalus conjunctus var. rickardii (Synonym: Astragalus reventus var. rickardii)

A close-up view of the maturing fruits plust 3 habitat views of Idaho milkvetch as seen on north-facing, grassland slopes above the John Day River at Cottonwood Canyon State Park..........May 3, 2017.
Paul Slichter