- Name also: Salt-marsh Sandspurrey, Salt-marsh Sand Spurrey, Salt Sandspurry
- Family: Pink Family – Caryophyllaceae
- Growing form: Short-lived perennial herb. Stout root.
- Height: 5–20 cm (2–8 in.). Stem limp–ascending, many-branched, woody at base, glabrous–upper part slightly glandular-haired.
- Flower: Corolla regular (actinomorphic), pink–white, 5–8 mm (0.2–0.32 in.) wide; petals five, 2.5–5 mm (0.1–0.2 in.) long, about same length as sepals. Sepals 5, elliptic, blunt, with membranous margins, dark at base. Stamens 2–8 (occasionally 10). Gynoecium syncarpous, with five styles. Flowers solitary in axils.
- Leaves: Opposite, stalkless, stipulate. Blade linear, blunt, short-tipped, fleshy, light green. Stipules widely triangular, membranous, shiny, united in pairs.
- Fruit: Egg-shaped, 4–6 mm (0.16–0.24 in.) long capsule splitting into 3 lobes. Seed winged–wingless.
- Habitat: Sea-shores, shoreside meadows, small rocky islands, salty land.
- Flowering time: June–September.
Salt sand-spurrey often grows on small rocky islands, on rocks that are sticking up through the water, and even occasionally on submerged ones. It anchors itself to cracks in the rock and between stones – it has no other option – with its very stout and deep-reaching root. The plant can stand the power of water, occasional submersion and sea salt. On mainland shoreside meadows at the bottom of muddy hollows this plant, which being so small is an otherwise poor competitor, can find a place to grow. Especially during summers, when the water level is generally lower, clay-rich and muddy shores form rich sand-spurrey stands. The species can even spread under the normal waterline, but these individuals are lost in the autumn when the water level rises again. Salt sand-spurrey also thrives on salty seashores, where the land has bad drainage and the salt doesn’t get washed away with the rain. In summertime the land can dry out and the salt content will rise to its former level, and sometimes the land becomes white with salt crystals. Only a few plants thrive on the shoreside salt belt, so small-sized salt sand-spurrey has enough space to grow. When the influence of sea-water weakens, vegetation that is salt-dependent declines and disappears as inland forest and bog vegetation takes over. Salt sand-spurrey disappears if the salt level drops too low in the upper parts of seashore meadows and in bays and estuaries that have low amounts of salt. It is occasionally found growing inland as virtually the only plant on acidicly poisoned clay ground.
Salt sand-spurrey flowers only open in sunny weather. Green, unopened, self-pollinating closed flowers can also be found, and self-pollination is probably common. Insect-pollinated plants certainly exist, which can be seen from the existence of sand-spurrey hybrids. At the same time, salt sand-spurrey can develop two different kinds of seeds: with and without membranous margins, the latter of which spread better on the shore winds.
One has to be careful with seaside sand-spurreys because red sand-spurrey (S. rubra) can also grow in the same place – salt sand-spurrey on the other hand can also grow casually inland. The species can be told apart by e.g. inspecting the membranous stipules at the base of the leaves. Red sand-spurrey is also hairier and its flowers have more stamens. Although Finland’s flora is known well, small plants in particular can be surprising: e.g. a third species of sand-spurrey, greater sea-spurrey (S. media), has recently been observed growing in the Åland Islands. Its stipules are like salt sand-spurrey’s, but the base of the stem is clearly woodier, and its flowers usually have more stamens (8–10).