- Name also: Birdeye Pearlwort (USA)
- Family: Pink Family – Caryophyllaceae
- Growing form: Perennial herb. Forming mat-like hummocks.
- Height: 3–8 cm (1.2–3.2 in.). Stem limp–ascending, rooting, usually glabrous.
- Flower: Corolla lacking or vestigial; sometimes petals 4(–5), white–reddish, shorter than sepals. Calyx regular (actinomorphic), green, approx. 5 mm broad; sepals 4(–5), blunt, in fruiting stage spreading, 1–2.5 mm (0.04–0.1 in.) long. Stamens 4(–5). Gynoecium syncarpous, with 4–5 styles. Flowers solitary. Flower-stalk nodding in budding phase and as capsule ripens. Buds spherical.
- Leaves: Opposite, stalkless, united in pairs. Blade thread-like, short-tipped, with entire margins, glabrous.
- Fruit: Almost round, yellowish gray, 4-valved capsule.
- Habitat: Yards, streets, paths, roadsides, small roads, lawns, ditches and banks on arable land, wasteland, rocky shores, meadows.
- Flowering time: June–September.
Procumbent pearlwort looks quite modest beside more colourful Pink family members, but it is capable of remarkable achievements. This native seashore plant persists in the wild without a care for the terrible storms that batter the outer bird rocks or unforgiving fissures in the lower parts of shore rocks. It has no fear of the concrete jungle that humans have created, tenaciously growing in cracks on church steps or holes in the pavement. It is even able to take root in vertical surfaces, where it hangs in beard-like tufts up to a couple of metres high. Its way of growing along the ground and its tenacious shoots make it able to stand continual trampling and intensive street cleaning. At the bottom of ditches and hollows procumbent pearlwort can be immersed in water for days without coming to any apparent harm. It is a common, if somewhat sparse, weed on arable land. Although the species is one of the most common urban plants, it often goes unnoticed and is becoming rarer. At its best it forms hummocks about as large as two hands, but it can grow as small as moss.
Procumbent pearlwort spreads efficiently through its branched rootstock and also by seed. The flowers are very modest: small and green. The corolla usually ranges from vestigial to almost non-existent, but the capsule’s brownish green lobes in the centre of the flower can be mistaken for petals. It is hard for the human eye to distinguish the flowers from the green background, and they probably don’t attract many insects. The plant self-pollinates, however, and produces a decent amount of seed from a whole summer of flowering. They stick to shoes and tyres, travel on running water or broken shoots, and are carried by the wind. It is no wonder that procumbent pearlwort has spread onto every continent except Antarctica.