Viola adunca is a species of violet known by the common names hookedspur violet, sand violet, and western dog violet. It is native to North America, including the western half of the United States to New England northward throughout Canada. This is a hairy, compact plant growing from a small rhizome system. The leaves are spade- or heart-shaped, sometimes with broadly wavy margins. They are generally 1 to 4 centimeters long. The single-flowered inflorescence grows at the end of a long, very thin peduncle. The nodding flower is a violet with five purple petals, the lower three with white bases and purple veining. The upper two petals may have hooked spurs at their tips. There are several varieties of V. adunca; a white-petaled form has been noted in Yosemite National Park.