Large-flowered pyrola is an evergreen herb in the wintergreen family (Pyrolaceae), which grows in the forest understory, ranging into meadows and tundra in the mountains. Large-flowered pyrola is distinguished by its large (relative to other wintergreen species) white flowers. Plants grow 5-20 cm tall from a rhizome. Large-flowered pyrola has only basal leaves that are broadly ovate to rounded, with a blunt, round or cordate base, and petioles longer than the blade. Leaves are leathery with slightly crenate margins. The inflorescence is unbranched with 4-12 flowers spiraled around a reddish stem. The perfect flowers have five large (6-10 mm long by 4-6 mm wide) white petals, often pinkish at the base. The flowers are open, flat to cup-shaped, the five petals spread apart. The petals are rounded with very finely serrate margins. The reddish sepals are narrowly triangular with membranous margins. The ten stamens have a yellow anther-covering and white filaments. The style is long-exserted from the flower and curved, with a ring below the stigma lobes. Flowers face out and slightly downwards. Fruits are globose capsules, 3-4 mm x 4-6 mm, containing many tiny seeds. Largeflowered pyrola can be distinguished from other members of its genus by its relatively large white flowers.
Pyrola grandiflora is a perennial with evergreen leaves, which turn a dark red color from the fall until early spring. It typically flowers in mid-summer.
Flowers are bisexual, and pollinated by bees. The anthers have two pores at the tip, which release pollen when vibrated by bees at a certain frequency. Self-fertilization is also possible, but has not been tested in field studies. When pollinated, flowers develop into reddish capsules, which look like flattened globes with the style still attached. The capsules split from the base, releasing ca. 1000 seeds to be dispersed by gravity and water. Plants also spread vegetatively by rhizomes.
Pyrola grandiflora is a circumpolar species that occurs across the northern half of North America: east from Alaska to Greenland Quebec and Labrador, including all the Canadian provinces except New Brunswick, Nova Scotia and Newfoundland. Pyrola grandiflora occurs across Alaska except for the Alaska Peninsula and Aleutian Islands and the southeast panhandle. In Denali, the species is most common in the northeastern foothills and floodplains of the park, but ranges widely in suitable habitat throughout, including both on sides of the Alaska Range crest.
This species has a bimodal elevational distribution: it is most frequent at 900-1100 meters, followed by 300-500 meters. This split probably reflects its preferences for different habitats, growing in both forests (low elevation) and moist tundra (high elevation). Additionally, within Denali, arctic wintergreen occurs is common on steep slopes (20-28 degrees) and low inclines (<4 degrees). Of those specimens on steeper inclines, they are more likely to be found on northern aspects.