- Name also: Field Chickweed (USA)
- Family: Pink Family – Caryophyllaceae
- Growing form: Perennial herb. Loosely mat-like, tufted.
- Height: 10–30 cm (4–12 in.). Stem ascending–erect, spreadingly and finely haired (crown also with glandular hairs), flowerless branches in axils.
- Flower: Corolla regular (actinomorphic), white, 1.5–2 cm (0.6–0.8 in.) broad; petals five, 9–13 mm (0.36–0.52 in.) long, approx. twice as long as sepals, shallowly 2-lobed. Sepals 5, elliptic, with glandular hairs, broadly membranous margins. Stamens 10. Gynoecium syncarpous, with 5 styles. Inflorescence 2-branched cyme, flowers 4–10.
- Leaves: Opposite, stalkless. Stem branches with subtending bracts often resemble leaf whorls. Blade narrowly lanceolate–almost linear, sharp-tipped, with entire margins, glabrous–short-haired, greyish green.
- Fruit: Cylindrical, straight, yellowish brown, 10-valved, 6–8 mm (0.24–0.32 in.) long capsule.
- Habitat: Hillside meadows, roadsides, field banks, pastures, wasteland, seeded lawns and park lawns.
- Flowering time: June–August.
Field mouse-ear was first found in Finland in the mid-19th century. This most vigorous species seems to have become common in the 1930s, but perhaps that’s rather when botanists began to view these new additions to Finland’s flora as being worthy of inspection. Field mouse-ear’s settling in to grow wild in Finland is connected with the replacement of natural meadows with seeded lawns and meadows: the species arrived with foreign grass seed, along with many other species. The way that field mouse-ear spreads so efficiently through its runners means that a single plant can create a wide stand. It can be deduced, however, from the way that it arrived, that it can also spread by seed. Its beautiful flowering time begins around midsummer and it can bloom until the beginning of the early autumn.
Field mouse-ear has not yet reached the limit of its habitat; new stands are still appearing. Its most common habitat are on culturally-influenced land, roadsides and sloping meadows. Common mouse-ear (C. fontanum), which thrives in dry meadows, is the most common species of the genus in Finland, but it has clearly smaller flowers than field mouse-ear and its petals are around the same length as its sepals. Field mouse-ear has not yet spread to Lapland. Alpine mouse-ear (C. alpinum) which grows there has large flowers and slightly broader leaves than field mouse-ear, but they otherwise look alike. Alpine mouse-ear quite often moves from its wild habitat to waste ground and banks.
Field-mouse-ear’s South European relative, snow-in-summer is one of the most popular plants in Finnish rock gardens. It often jumps the fence into the wild or ends up growing among garden rubbish on nearby rocks.