This grower is sure of this plant identification.
Greater stichwort, Stitchwort
Stellaria holostea (Greater stichwort). This perennial species has thin stems and finely pointed leaves. The large flowers are white and bloom in the spring. This plant is often found in the wild in Northern Europe. STEM: Turning upwards, slender at base. ROOT: Slender, creeping stock. HAIRS: Hairless or hairy above. STIPULES: Absent LEAF-STALK: Absent BRACTS: Leaf-like FLOWER STALK: Longer than flower SEPALS: 5, spear-shaped, with narrow papery edge. PETALS: 5, equal, split to about half-way. STAMENS: 10 STIGMA: 3 OVARY: 1, 1-celled SEEDS: Numerous, kidney shaped with tiny outgrowths.
They will prefer to be grown in full sun with rich moist, slightly acidic soil. Propagate from seed or cuttings.