(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.