- Name also: Snowline Wintergreen, Lesser Wintergreen
- Family: Heather Family – Ericaceae
(formerly Wintergreen Family – Pyrolaceae)
- Growing form: Perennial wintergreen herb. With subterraneous runners.
- Height: 5–20 cm (2–8 in.). Stem glabrous.
- Flower: Corolla spherical, virtually closed, white–reddish, 5–7 mm (0.2–0.28 in.) long; petals 5. Calyx 5-lobed, lobes triangular. Stamens 8 or 10. Pistil a fused carpel, single-styled (stigma 5-lobed), body straight, flower remains inside. Inflorescence erect, compact, 5–10-flowered raceme, flowers nodding.
- Leaves: In a basal rosette, stalked, overwintering. Stalk winged, same length or shorter than blade. Blade widely elliptic–round, shallowly toothed, quite thin, leathery. Stem leaves alternate on base, small, stalkless, scaly.
- Fruit: 5-valved, nodding capsule.
- Habitat: Young, broad-leaved and slightly boggy forest heaths, bog margins, swamps, fens, edges of forest ditches, fell heaths.
- Flowering time: June–July.
Common wintergreen is the most common species in its genus in Finland. It grows across the whole country, but demands a certain amount of dampness to thrive. The broadest and most coherent stands are in rich, boggy forests, swamps, bog margins and places subject to coastal accretion. Common wintergreen can be found at the bottom of wet pits in areas that are dominated by dry forests. It encroaches into areas of tundra on the Lappish fells, but it only manages to flower at the end of summer in its northernmost habitats, and it only produces seeds under the most favourable conditions. The tiny seeds can however travel on the wind, so the tundra wintergreen population can be complemented from the bottom of the fell. The dust-like seeds provide no spare nutrition at all for the developing shoot, which must rather find a fungal mycelium just to get a start in life. With the help of a symbiotic mushroom common wintergreen develops a rudimentary underground stem, which can keep growing underground for years before forming a shoot. Common wintergreen’s rootstock is quite simple because the mushrooms take care of assimilating water and nutrition throughout its life. There is a busy exchange of substances going on at the contact point between the mushroom and the root because the mushroom receives sugars that the plant has assimilated in return for its services.
There are four real wintergreens, i.e. species that belong to genus Pyrola, that grow in Finland. These have in common a loose basal rosette, from the middle of which an erect inflorescence ascends with pale nodding flowers. The stem also remains typically upright throughout the winter and the seeds fly from the capsule on gusts of winter wind. Although common wintergreen is often smaller than its relatives, the species are easiest to tell apart during their flowering time. Common wintergreen’s flower is almost closed. The plant lacks both nectar and fragrance so insects are rare visitors. The flower self-pollinates as a safety measure, and its pistil’s short, straight body doesn’t push the bud-like stigma outside the flower. Sometimes cross-pollination occurs, resulting in hybrids with round-leaved wintergreen (P. rotundifolia) too.