Flower:

Flowers are slightly irregular and solitary at the end of a naked stalk, ½ to ¾ inch across, 5 yellow petals with dark purplish lines at the base of the lower petals that act as nectar guides. The 2 lateral petals may be hairless or have a few short hairs at the base (slightly bearded). The backs of the upper petals are often tinged purple.

Leaves and stems:

Leaves are lance to egg-shaped, up to 2½ inches long, usually at least 3 times as long as wide, blunt or pointed at the tip and often abruptly tapering at the base, toothless, with short hairs all around the edge and on the leaf stalk. Leaves appear to be mostly basal, though the flowering stems arise from leaf axils near the base of the plant with multiple stems arising from the underground rhizomes.

Notes:

One of two yellow violets in Minnesota, this rare species is found on prairie moraines while Downy Yellow Violet (Viola pubescens) is a common woodland species.  According to the DNR, Yellow Prairie Violet was first discovered in Minnesota in 1981, not that long ago, and classified as a Threatened species in 1996 due to its rarity in the state. Its preferred habitat is also the preferred type of site for gravel mining and/or grazing, which puts the species at risk. When we went in search of it ourselves, we were disappointed to find most of the sites where it had been previously found were no longer there—they had all been turned to pasture or industrialized with nary a native species left. Luckily the DNR had the foresight to snatch up some land in western Lac Qui Parle county where this little gem still has a chance to thrive.