- Name also: Arctic Starflower (USA)
- Latin synonym: Lysimachia europea
- Family: Primrose Family – Primulaceae
- Growing form: Perennial herb (not wintergreen). Rootstock thin, creeping, many-rooted.
- Height: 5–20 cm (2–8 in.). Stem unbranched, glabrous.
- Flower: Corolla regular (actinomorphic), wheel-shaped, white or sometimes light reddish, 11–19 mm (0.44–0.76 in.) wide, fused, deeply (5–)7(–9)-lobed. Calyx lobes narrow, sharp-tipped, often reddish. Stamens 7. Pistil a fused carpel. Flowers 1(–2), long-stalked, usually solitary.
- Leaves: Most leaves like a rosette at top of stem, almost stalkless, clearly different sizes. Leaf blade lanceolate–obovate, glabrous, thin. A few small leaves possible under rosette.
- Fruit: Globose, bluish grey, net-patterned, valved capsule.
- Habitat: Dry and young forests, broad-leaved forests, swamps, fens, wooded meadows, banks, fell heaths.
- Flowering time: May–July.
Chickweed wintergreen grows from the rocky outcrops of the Finnish archipelago to the northern tundra of Lapland, and is especially common in young and broad-leaved forest heaths. There are extremely few Finnish plants that have such a broad-ranging habitat. Despite this, however, chickweed wintergreen mutates little, although sometimes narrower-leaved or reddish-flowered plants can be found.
Chickweed wintergreen’s sexual reproduction is quite inefficient. The only insect that is in any way interested in its flowers are the Melanostoma mellinum flower fly, but pollinators are rarely seen at its flowers. The seeds rarely develop and hardly ever germinate among the crowded plants. The species propagates more efficiently through its runners, which each plant develops two or three, over one metre long. As with other pioneer plants, these runners help the species efficiently colonise disturbed earth like logging areas. Chickweed wintergreen is however also able to grow in relatively shady areas: the leaves of the crown rosette do not cover each other, so they are able to make use of little light. In the dark backwoods the beauty of the shining white flowers has inspired poets and story-tellers, and even the father of contemporary botany Carl von Linné praised the beautiful simplicity of the flowers.