Sandworts are annual to perennial herbs with opposite, linear to broad (sometimes fleshy) leaves without stipules. Most of our plants are 10 cm tall or taller. The flowers are usually born in open and diffuse to narrowed clusters, only occasionally are they single and terminal or in the axils of barely reduced leaves. The flowers are rather small, usually complete, or lacking petals, sometimes functionally either male or female. There are 5 sepals, which are free or joined only at the base, 1- to 3 nerved. There are 5 white petals, from 2 or 3 times as long as the calyx to greatly reduced or lacking, entire to slightly shallowly notched, but not 2-lobed. There are usually 10 stamens, inserted with the petals at the edge of a very slightly developed to fairly prominent, glandular disk surrounding the ovary. There are usually 3 styles. The capsule is 1-celled, few- to several-seeded, splitting open by 6 valves, which are membranous to firm or moderately stiffened. The seeds are plump to flattened and more or less wing-edged. The genus consists of nearly 200 species, widely distributed and found under a wide range of habitats, as from swampy and often saline areas to montane rock slides. The name comes from the Latin arena, sand, because of the often sandy habitat.
Guide to Identify Presented Species of Genus Arenaria
FLOWERS IN OPEN CLUSTERS
A. serpyllifolia Thyme-leaved Sandwort Low-growing, branching, delicate herb, growing on dry or sandy ground.
Flowers small, white. Sepals are pointed, 3-4 mm long, longer than petals.
Leaves short, lance- to egg-shaped, stalkless, without hairs on edges.