The Small Northern Yellow Lady's Slipper is Cypripedium parviflorum var. makasin, very similar to the Large Yellow Lady's Slipper, Cypripedium parviflorum var. pubescens, and in many cases very difficult to distinguish from that variety.
Generally its flowers are smaller, 2-3 cm, are more richly colored and have a much stronger scent that the other variety, but the main difference is that the lower sheathing bract is hairless or nearly so. The two varieties intergrade, however.
The plants are usually about 30 cm tall and, like variety pubescens, prefer moist areas along streams and lakes with some protection provided by open woodlands and thickets. Both varieties are very rare in the state of Washington.