Viola adunca

From Oregon Flora, Gardening with Natives:

Early blue violet or hookedspur violet has sweet periwinkle to deep purple flowers nodding above rosettes of daintily cupped leaves. This diminutive groundcover is a larval host plant to a number of endangered butterflies in the Pacific Northwest and is often used in butterfly habitat restoration projects. The fragrant flowers can also be used to liven up a garden salad or to add a floral garnish to a cake. This little plant has a high tolerance for salt spray, fluctuating moisture levels, and disturbance, but appreciates soils with high organic matter.