The photo above shows the purple-lined banner and wings of Lyall's milk-vetch as seen on sandy ground along the Columbia River near Priest Rapids Dam, central Washington........April 30, 2007.
Lyall's milk-vetch is an erect perennial wildflower with several thin, branched stems clustered on a short, woody base and rising 10-20 cm high. The leaves and stems are variously pubescent, with grayish hairs that are soft, silky and appressed, stiff, sharp and appressed, or woolly and spreading. The ascending, pinnately compound leaves are 3-11.5 cm long with 11-21 leaflets that are lance-linear, linear-elliptic, or narrowly oblong in shape with acute, obtuse (lower leaflets) or rounded tips. The leaflets range from 8-15 mm long.
The loosely flowered racemes are axils and about equal to or longer than the upper leaves. The stout pedicels are 1 mm long while the woolly, bell-shaped calyx measures 5 mm long with linear teeth that are up to twice as long as the calyx tube. The whitish to pale lavender corolla is 6-8 mm long with purple-lined wings and banner. The narrow banner is well-reflexed and measures 4.5-7.5 mm long. The pod is lance-oblong in outline, slightly compressed, and 6-7 mm long and somewhat heart-shaped in cross-section. The pods are somewhat glabrous to woolly-haired.
variety caricinus: Lower stipules clasping or joined with a fringed margin while the upper ones are triangular and not joined. Pods 6-8.5 mm long and 2-3 mm wide. Raceme shorter, flowering only from the upper 2-5 nodes.
variety lyallii: All stipules triangular, not joined. Pods 5-8 mm long and 2-3.5 mm wide. Raceme longer, flowering from the upper half of the stem.
Lyall's milk-vetch is found on sandy slopes and among sagebrush in the basin valleys and on low hillsides.
Lyall's milk-vetch is found from Kittitas County in central Washington south along the Yakima and Columbia Rivers to south-central Washington and upstream along the Snake River to southeastern Idaho and northeastern Malheur County in eastern Oregon.
The photo above shows a close-up of the upper stem and inflorescence of lyall's milk-vetch as seen in sandy soils south of Priest Rapids Dam.......April 30, 2007.
The photo above shows a close-up of a stem leaf of lyall's milk-vetch as seen in sandy soils south of Priest Rapids Dam.......April 30, 2007.
The photo above shows a close-up of the pinnately compound leaf of Lyall's milk-vetch as seen about 2 miles west of the Vernita Bridge on the east bank of the Columbia River in south-central Washington ........March 29, 2007.
The photo above shows a close-up of the leaflets of Lyall's milk-vetch as seen about 2 miles west of the Vernita Bridge on the east bank of the Columbia River in south-central Washington .........March 29, 2007. Note the numerous whitish hairs covering the surface of both the leaflets and stem.
The photo above shows the form of Lyall's milk-vetch as seen south of Priest Rapids Dam, central Washington.........April 30, 2007.