Atocion armeria aka Sweet William Catchfly

Atocion armeria is in the pink family, Caryophyllaceae. It is native from Poland into eastern Europe. It grows in temperate zones. It is not native to Britain or Ireland. The RHS gives Silene armeria as a synonym. Names include sweet william catchfly and bunch pink. Another name is mock sweet william. Plants that escaped gardens now grow in parts of North America. These include the east, the centre, and the Pacific Northwest.

This small plant has upright stems and a narrow spread. In gardens, it grows about 1–1.5 feet [0.30–0.46 metres] tall. It spreads about 0.75 feet [0.23 metres] wide. Its stems bear grey-green leaves. These range from oval to lanceolate, or lance-shaped. They reach 0.25 feet [0.08 metres] long. Leaves at the base are oblanceolate: wider towards the tip. These leaves tend to wither by midsummer. The sticky stems can trap small insects. This trait gives the plant its name, catchfly.

Flowers range from rose-pink to magenta. They form rounded cymes, or flower groups, with flat tops. Each bloom is about half an inch across. Each has five petals with a shallow notch. Missouri Botanical Garden gives July to August as the bloom season. The blooms add colour to beds and annual borders. The plant's small size fits these spaces well. Its upright stems hold blooms above the leaves.

Grow it in full sun or part shade. It likes sun with some shade in the afternoon. Average soil suits it if water drains well. It grows in sand or gravel, with dry to medium moisture. Good drainage counts more than rich soil. It copes with drought and dry ground. It does not grow well in the Deep South's hot, humid summers. Missouri Botanical Garden lists USDA hardiness zones 5–8.

Kew lists this species as an annual, which lives one year. Missouri Botanical Garden also calls it a herbaceous perennial. That means a plant with soft stems that lives for years. US growers use it as a cool-season annual or biennial. A biennial lives for two years. Sow indoors eight to ten weeks before the last spring frost. Or sow outdoors in autumn or early spring. In spring, aim about three weeks before the last frost. Plants may self-seed where the soil and climate suit them. This can yield new plants with no need to sow again. Missouri Botanical Garden reports no major insect or disease problems.