Pursh's Wallflower
(Douglas or Western Wallflower)
Erysimum capitatum Douglas ex Hook var. purshii (Durand) Rollins

Collected apparently northeast of Kamiah in Idaho Co., Idaho, 1 Jun 1806. (Source)

Biennial/Perennial, it ranges from just a few inches tall to well over two feet. Although it is most often a vibrant lemon yellow, it can be almost white. It is relatively solitary, growing isolated from other members of its own and other species. At lower elevations Wallflower blooms in the very early spring, often under Junipers; later in the summer it can be found above tree line in open dry flats and hillsides, and open meadows. It is in flower from July to August.

The plant prefers light (sandy), medium (loamy) and heavy (clay) soils, requires well-drained soil and can grow in nutritionally poor soil, such  neutral and basic (alkaline) soils. It cannot grow in the shade. It requires dry or moist soil. It is found throughout Western North America at elevations from 300-3000 feet.

Medical Uses
A preventative against sun burn, the plant was ground up then mixed with water and applied to the skin. It relieves the pain caused by overexposure to heat. A poultice of the whole pounded plant has been applied to open fresh wounds and rheumatic joints. An infusion of the whole plant has been used as a wash on aching muscles. The crushed leaves have been sniffed as a treatment for headaches. A poultice of the warmed root has been applied to treat the pain of toothache. An infusion of the crushed seed has been drunk and used externally in the treatment of stomach or bowel cramps. (Source)