- Family: Heather Family – Ericaceae
(formerly Wintergreen Family – Pyrolaceae)
- Growing form: Perennial herb. With subterraneous runners.
- Height: 10–30 cm (4–12 in.). Stem glabrous.
- Flower: Corolla campanulate, white–reddish, 7–10 mm (0.28–0.4 in.) long; petals 5. Calyx 5-lobed, lobes triangularly ovate. Stamens 10. A single carpel (stigma 5-lobed), body straight, often oblique, protruding from flower. Inflorescence erect, usually over 10-flowered raceme, flowers nodding. Often flowers sparsely.
- Leaves: In a basal rosette, stalked, overwintering. Stalk winged, same length as blade or shorter. Blade round–elongated, with rounded teeth (crenate), hard, thick, bumpy. Stem leaves alternate at base, small, sheath-like–scaly.
- Fruit: 5-valved, nodding capsule.
- Habitat: Young and dryish forest heaths, hillside forests, ridges.
- Flowering time: June–July.
- Endangerment: Near threatened.
Intermediate wintergreen looks like a cross between round-leaved wintergreen (P. rotundifolia) and common wintergreen (P. minor), especially with regards to its flower. It has probably come about as a cross between round-leaved and common wintergreen, and its number of chromosomes has doubled. This means that intermediate wintergreen can propagate itself like a regular species and it produces seeds that are capable of growing. The hybrid has been created several times because intermediate wintergreen also grows in the Himalayas as well as Europe. Wintergreens can spread over considerable distances because its extremely small seeds float off even on weak air currents. Wintergreen seeds are amongst the smallest in the plant kingdom: a single gram contains approximately a quarter of a million seeds.
Intermediate wintergreen is quite common in southern Finland and becomes rarer the further north one goes. In Lapland it is very rare, but even in Finland’s north-western “arm” in Kilpisjärvi there are small patches, even if they don’t form very big stands. Stands are usually concentrated in moraine territory, light-filled pine woods and rocky ridges.
Compared to round-leaved wintergreen, intermediate wintergreen’s leaf blades are not roundish at all, but rather peculiarly bumpy. Like common wintergreen the corolla is campanulate and it has similar colouring, but the flower is larger and the body of the pistil is clearly distinct from the flower. Cross-breeding between round-leaved and common wintergreen results in a plant that looks like diminutive intermediate wintergreen. The hybrid’s flowers are smaller than intermediate wintergreen’s, and as a legacy from round-leaved wintergreen the body of the gynoecium is slightly curved while intermediate wintergreen’s is straight. The sterile hybrid does not develop any seeds: its corolla and stamens remain on the flower even right through the winter.