The photo above shows sulphur lupine as seen from BLM lands at Wilson Creek, near Wilbur, WA (Lincoln County)........April 30, 2007.
Sulphur lupine is a perennial lupine to 10 dm tall. It tends to have basal leaves present during flowering, with the lower leaf petioles 3 to 5 times longer than the leaflet blades, while the upper stem leaves may have petioles shorter than the blades. The compound palmate leaves may have from 9 to 11 narrow, oblanceolate leaflets with acute tips. The leaflets may be hairless above and sparsely to very hairy beneath, or they may be equally very haired on both surfaces (See photos below for the leaves of L. s. var. sulphureus). Variety subsaccatus tends to have pubescence on both leaflet surfaces.
The flowers are bluish or purple (variety sulphureus has yellow flowers) and found on 6 to 15 cm long racemes (usually less than 10 cm in variety subsaccatus. The calyx is silky and it is asymetrical although it isn't spurred. The upper lip of the flower is bidentate, while the lower is entire. The banner isn't reflexed very much from the wings or keel. Individual flowers range in length from 9-12 mm.
Variety sulphureus shows a wide range of flower color, usually being yellow but ranging from nearly white, faint yellow, and occasionally blue.
Sabin's Lupine (Lupinus sabinii)- Sabin's Lupine, like the yellow-flowered form of Sulphur Lupine may be found in the Blue Mts of Oregon and Washington. Both have banners which are sparsely to non-haired on the dorsal surface. Characteristics which help distinguish Sabin's from Sulphur Lupine include larger flower size (15-18 mm) and the fact that Sabin's Lupine usually lacks any basal leaves at the time flowers bloom. The petioles of the lower leaves on Sabin's Lupine are at most twice the lengths of their leaflets, while the petioles of the lower leaves on Sulphur Lupine may be 3-5 times longer than the leaflets.
Sulphur lupine may be found on prairies and sagebrush desert from the foothills into the lower mountains.
Sulphur lupine ranges from British Columbia south along the eastern edge of the Cascades to California, and ranges eastward to Idaho. It may be found down the Columbia River to the Willamette River Valley, and into southwestern Washington.
Sulphur lupine as seen on Sourdough Ridge, Asotin Wildlife Area, Asotin County, WA..........June 3, 2017.
Upper leaf surface (left) and lower leaf surface (right) of sulphur lupine from the upper Gronde Ronde River, F.S. Rd #51, Wallowa-Whitman N.F.........June 23, 1998.
Close-up images of the flowers of sulphur lupine as seen on the eastern outskirts of Odessa, WA.........April 28, 2007.
Sulphur lupine beginning to bloom on the eastern outskirts of Odessa, WA.........April 28, 2007.
- -Sulphur lupine as seen along US Highway 30 west of Deadman Pass, Umatilla County, OR..........June 13, 2018.