[Milkvetch: The Genus Astragalus East of the Cascade
Mountains of Oregon and Washington]
Basalt Milkvetch, Idaho Milkvetch, Idaho Milk-vetch, Stiff Milkvetch
Astragalus conjunctus var. conjunctus
Synonyms: Astragalus diversifolius var. campestris, Astragalus reventus var. conjunctus, Homalobus campestris
Idaho milkvetch as seen at the high point on Bakeoven Road to the northwest of Shaniko, OR..........May 14, 2010.
The
photo at right shows a frontal view of the flower of Idaho milk-vetch. Note the
purplish veins on the front of the banner of this flower, as well as the purplish
tip to the keel. Photographed just west of Condon, Oregon.........April
30, 2000.
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 smooth-skinned (glabrous), 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 - 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.
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Additional close-up photos of Idaho milk-vetch as seen from about one mile east of the summit of Oregon Highway 218 between Clarno, OR and Fossil, OR.........May 16, 2010.
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Close-up photos of a nice cluster of what may be Idaho milkvetch (variety conjunctus) as seen on slopes near Simcoe Butte in northern Klickitat County........June 16, 2007. Variety conjunctus is currently not recognized as being found in Washington. Other plants seen in these views include Eriogonum ovalifolium and Erigeron bloomeri. Note the close-up side view of the corolla with its purple tip to the keel. Note also the numerous hairs on the surface of the calyx. The calyx tube is cylindric, about twice as long as wide. The ovary is glabrous.
The photo above shows a leaf of Idaho milk-vetch. The leaflets are narrowly linear in outline and number between 13 and 37 per leaf.
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The photos above show close-up views of Idaho milk-vetch? as seen south of the John Day River along South Twickenham Road in north-central Oregon.........April 8, 2007. The flowers at this location seem to be slightly smaller than those seen at other Oregon locations.
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The photos above show close-ups of Idaho milk-vetch as seen south of Condon, OR along Carter Hill Road, just west of its junction with Ramsey Canyon Road.........May 28, 2007.
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Idaho milkvetch as seen along the Rimrock Springs Trail #850, Crooked River National Grasslands..........May 20, 2017.
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Close-ups of Idaho milkvetch as seen at the high point on Bakeoven Road to the northwest of Shaniko, OR..........May 14, 2010.
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Idaho milkvetch as seen (left) on Calamity Butte, Malheur National Forest.......July 18, 2010. The photo at right shows Idaho milkvetch as seen along the Gray Butte Trail #852, Crooked River National Grassland..........May 20, 2017.
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The photos above show close-up views of what is probably basalt milk-vetch as seen south of the John Day River along South Twickenham Road in north-central Oregon..........April 8, 2007. Note the long calyx tube (at least 2 times as long as wide), the narrow leaflets which number less than 23. and the long banner and wing petals. The flowers at this location seem to be slightly smaller than those of Idaho milk-vetch (Astragalus conjunctus var. conjunctus) seen at other Oregon locations.
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Additional close-up views of what is probably basalt milkvetch as seen amongst bunchgrasses at Camp Hancock about 2 miles east of Clarno, OR..........May 15, 2010. Note again the long, narrow leaflets which in this individual number about 11, the glabrous dorsal-ventrally flattened pod which is held nearly erect on the stem and long wing and banner petals on the flowers. A return to one of the sites where this species is seen is necessary to gain evidence of the type of stipules found at the base of each of the lower stem leaflets to help identify the plants.
Paul Slichter