- Name also: Longleaf Starwort (USA)
- Family: Pink Family – Caryophyllaceae
- Growing form: Perennial herb. Often forms dense stands.
- Height: 15–25 cm (6–10 in.). Stem ascending, abundantly branched, 4-edged, rough at least at base.
- Flower: Corolla regular (actinomorphic), white, 4–8 mm (0.16–0.32 in.) broad; petals 5, deeply 2-lobed (looks like 10 petals), 2–3 mm long, same length as sepals. Sepals 5, glabrous, unclearly veined. Stamens 10. Gynoecium syncarpous, with 3 styles. Inflorescence an abundantly flowered, 2-branched cyme; subtending bracts membranous, glabrous.
- Leaves: Opposite, stalkless. Blade linearly lanceolate–narrowly obovate, with entire margins, light–lime green, basal part often sparsely hairy, margin and central vein rough.
- Fruit: Egg-shaped, light brown–brownish red, 6-valved, 4–5.5 mm (0.16–0.22 in.) long capsule.
- Habitat: Young fir groves, logging areas, rocky hillside broad-leaved forests, foot of precipices, stream-side hedgerows, springs, grassy swamps.
- Flowering time: June–July.
Long-leaved stitchwort can be found in almost all of Finland. In the northern half of the country, north of a line that runs from Oulu south-east towards Kitee, it is rare, but in the southern half of the country it grows unevenly – perhaps it is spread somewhat randomly by plant-eating animals or maybe germination requires something as yet unexplained. Long-leaved stitchwort seems to be concentrated in the margins of rich areas that have a lot of swampy spruce forest. It is common especially in rich forests, shore-side hedgerows and swamps, and stands often form beside tree stumps and stones, and often on top of them. Long-leaved stitchwort can sometimes run riot locally in the wild when the forest is cut to make way for e.g. power cables, but logging and changes to the natural forest have hardly helped the species’ position.
Long-leaved stitchwort looks like lesser stitchwort (S. graminea), but it is a lighter green and has a clearly smaller flower, and its sepals are glabrous. Long-leaved stitchwort’s appearance varies however depending on where it is growing. In light-filled and open places it is greyish with erect, narrow leaves. In shady places it is lime green and its leaves are spreading and broad. Long-leaved stitchwort’s star-like flowers do not twinkle very long as its petals are only a few millimetres long. It flowers abundantly, however, and for a long time, even in very shady places.