Synonym: Arenaria macrophylla
Big-leaf sandwort is a small perennial with numerous slender rhizomes which forms loose mats or patches of plants. The stems are spreading to erect and often branched. They rise 5-15 cm high and are 3 to 4-angled in cross-section. The numerous leaves are linear-elliptic to linear-lanceolate in shape with acute tips. The leaves range from 2-5 cm long and 3-15 mm wide.
The 2-5 flowers are found in loose, bracteate cymes at the leaf axils and terminus of the stems. The slender pedicels are up to 3 cm long. The sepals are ovate-lanceolate in shape with pointed tips and measure 3-5 mm in length. The 5 white petals range from shorter than the sepals to half again as long as the sepals.
Big-leaf sandwort is a plant of moist to dry, shaded to open woods, meadows and rocky slopes.
Big-leaf sandwort may be found from British "Columbia southward along both sides of the Cascade Mts. to California. It may be found eastward to Labrador and the Atlantic coast, and south through the Rocky Mts. to New Mexico.