Cascade grass-of-Parnassus is an attractive perennial wildflower with single or clustered stems from 11.5-35 cm high arising from a cluster of basal leaves atop a stout rootstock and elongated rhizomes. The herbage of both the stems and leaves is glabrous. An ovate leaf from 4-16 mm long may be found clasping the stem above midstem. The blades of the basal leaves are ovate to broadly ovate, or sometimes kidney-shaped. They measure 1.5-5 cm long and 1.3-4.9 cm wide. The base of the blade tapers gradually or abruptly to the broad petiole while the apex is rounded (sometimes with a small point) at the tip. The leaf blades are slightly longer than wide. The petioles are 1.7-9.5 cm long and are sometimes fringed at their base.
The white flowers are solitary at the top of the stems. The petiole is 6.5-12 mm long while each of the 5 sepals is lanceolate-elliptic with obtuse to rounded tips, each measuring 4-6 mm long and 2.5-3.5 mm wide. Each sepal may be entire or somewhat fringed or thinly toothed along the lower third of the margin. Each of the 5 oblanceolate to ovate petals are 9-15 mm long, 4.8-9.8 mm wide, and each has 5-7 veins. The margins of the lower half of the petals are fringed, the fringes from 1-3 mm long (and broader at the base than those of Parnassia fimbriata var. fimbriata. The fringes are typically found above the claw to about the middle of the petal, and occasionally above. Five fertile stamens are found spreading between the petals. The filaments of fertile stamens are 4.5-7.5 mm long and white in color. The yellow anthers are 1.5-3 mm long and attached at the middle of their ventral surface. In addition, the flowers have sterile stamens (known as staminoda) which are 3.5-5.2 mm long. The tips of the staminodes are divided into 7-12 long, thin lobes up to 3 mm long, each being globe-tipped. The styles, which are very short or almost absent, are divided into 4 styles up to 1.5 mm long.
Fringed Grass-of-Parnassus: Parnassia fimbriata var. intermedia - Leaves basal and broadly heart- or kidney-shaped. Leaf margins entire. Flowers large and showy, with 5 white petals which are fringed at their bases. Staminodia short and thin - at least 12 staminodial segments present.
Fringed Grass-of-Parnassus: Parnassia fimbriata var. fimbriata - Leaves basal and broadly heart- or kidney-shaped. Leaf margins entire. Flowers large and showy, with 5 white petals which are fringed at their bases. Staminodia short and thick.
Fringed Grass-of-Parnassus: Parnassia fimbriata var. hoodiana - Leaves basal and broadly heart- or kidney-shaped. Leaf margins entire. Flowers large and showy, with 5 white petals which are fringed at their bases. Staminodia longer and thinner, less than 10 staminodial segments present.
Cascade grass-of-parnassus may be found in marshes, seeps, bogs, wet meadows and along streams from 2000-3100 meters of elevation in the lower mountains up to the alpine zone. Associated species are Senecio triangularis, Caltha biflora, Viola palustris and especially Scirpus microcarpus (at least in Washington populations). Because of their wet habitat, they will be in areas surrounded by Alnus viridis or Salix species, or occasionally be found under those shrubs when light is able to get under them.
Cascade grass-of-parnassus may be found from the Cascade Mts. of southern Washington and northern Oregon south to the San Bernardino and San Gabriel Mts. of California and east to the Steens Mt. of southeastern Oregon, southern Idaho, and northern and central Nevada.
In the Columbia River Gorge, it may be found between the elevations of 2700'-3400' between Larch Mt. and Nesmith Pt.
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