Flower:

Flowers are white, ¾ to 1 inch across, single at the end of a long, slender stem. The 5 petals are oval to egg shaped with conspicuous veins that come just short of the edges, a few veins may be faintly branched. The egg-shaped ovary of the central pistil is white with a 4-parted stigma at the tip, surrounded by 5 stamens that are more than half as long as the petals and spread out between the petals. Stamen tips are creamy white, quickly turning brown then falling off. Between the fertile stamens, at the base of a petal, is a spreading array of 5 or more (typically 12 to 14) greenish to yellow sterile stamens, the longest more than ½ the length of a fertile stamen, and tipped with green to yellowish glands. The 5 spreading sepals behind the flower are green, oblong with visible veins, ½ or more the length of a petal and visible between the petals.

Leaves and stems:

Leaves are leathery, mostly basal, the blades mostly broadly heart-shaped, up to 1¼ inches long and nearly as wide, toothless, hairless, blunt or tapered to a point at the tip, on a stalk 1 to 2 times as long as the blade. A single stem leaf, when present, is at or below the middle of the stem or nearly at the base, the blade about as large as or sometimes larger than the basal leaves, often more sharply pointed at the tip, and stalkless with the rounded basal lobes clasping the stem. The wiry flowering stem is angled and hairless.

Notes:

Marsh Grass-of-Parnassus is one of two Minnesota Parnassia species. Both are considered indicator species of fen habitats and like them, increasingly rare, and is listed as a Threatened species in Wisconsin. While their ranges overlap somewhat in northwestern counties. P. palustris inhabits rich or spring fens in north central and north eastern counties and American Grass of Parnassus (P. glauca) prefers calcareous fens in southern and western regions of the state. While very similar in growth habit and flower, the two are easily distinguished by several obvious differences. By comparison both basal and stem leaves of P. glauca are less heart-shaped, the stem leaf typically rather smaller than basal leaves. The flower sepals are only about ¼ as long as the petals, and the sterile stamens between the 5 fertile stamens are shorter and always clustered in 3s. Of note is that other references state the stem leaf of P. glauca is not clasping, but from our own photos and personal observations it may seem nearly so.