Arcane Milkvetch
Astragalus obscurus
Synonym: Astragalus miser
The photo above shows a close-up of the front
of the veined banner and the central wings surrounding the keel of arcane milk-vetch.
Photographed along Oregon Highway 78 at the county line between Hareney and
Malheur Counties..........May 29, 2000.
The
photo at right shows a close-up of the flower of arcane milk-vetch. Photographed
along Oregon Highway 78 at the county line between Hareney and Malheur Counties.........May
29, 2000. Note the abruptly incurved keel which is angled approximtely 90 degrees upwards.
Characteristics:
Arcane milk-vetch is a perennial wildflower with a cluster of spreading to
erect stems from 5-15 cm tall. The leaves and stems are greenish and minutely
haired with the hairs stiff and appressed to the stem or blade. The pinnately
compound leaves are 3.5-10 cm long with 7-13 leaflets that are linear to oblong-elliptic
in outline and 2-12 mm long. The leaf petioles are slender but stiff.
The inflorescence is a 5-15 flowered raceme from 1-6 cm long. The bell-shaped
calyx is 3.5-5.5 mm long with black and white hairs appressed to the tube. The
narrow to broad calyx teeth are awl-shaped and measure 0.4-1.6 mm long. The
corolla is whitish-yellow, dirty white or whitish tinged with lilac. The banner
is 7-10.5 mm long while the wings are up to 9.5 mm long while the keel is slightly
longer than the wings. The nearly sessile pod is held erect. It is linear-oblong
in outline and straight, and measures 12-25 mm long and 2.5-3.5 mm wide.
Habitat:
Arcane milk-vetch may be found on rocky flats, hillsides and ridge amongst
low sagebrush between the elevations of 1100-2400 meters.
Range:
Arcane milk-vetch may be found from the Burnt, John Day and Deschutes Rivers
of central Oregon and southward to the foothills to the east of the Cascade
Mts. of California. It is found eastward through southeastern Oregon to southern
Idaho and northern Nevada.
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Arcane milk-vetch blooming on rocky flats near the summit ridge of Hart Mt. to the west of Hot Springs Campground, Hart Mt. National Antelope Refuge........June 9, 2016.
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Additional images of arcane milkvetch as seen on gravelly slopes at Domingo Pass in the Pueblo Mountains of southeastern Oregon.........May 31, 2012.
The photo above shows a close-up of the leaf
of arcane milk-vetch photographed about 2 miles south of Frenchglen, OR..........May
27, 2000.
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Arcane milk-vetch as seen in mid Fall on north-facing slopes of Sulphur Ridge in the South Fork Crooked River Wilderness Study Area...........October 25, 2015.
The photo above shows a close-up of the pods of arcane milk-vetch
photographed about 2 miles south of Frenchglen, OR..........May 27, 2000.
The photo above shows the scurfy surface to the leaflets of arcane
milk-vetch. Photographed near Picture Rock Pass on Oregon Highway 31..........July
12, 1998.
Paul Slichter