Plants annual, not rhizomatous, stoloniferous, or bulbiferous. Stems erect, branched or simple, 2-30 cm. Leaves alternate, erect, not distinctly petiolate, with clasping leaf sheaths; blade linear, 2-60 × 1-4 mm. Inflorescences terminal, 1-bracteate; bract linear to oblanceolate, to 20 × 2 mm. Flowers 2-8; sepals 3-7 mm; petals 5, white, 4-6 mm; stamens 3-5, anther yellow. Seeds 1.2-2.6 mm, tuberculate; elaiosome absent. 2n = 28.

Flowering spring. Dry to moist habitats, coastal and inland valleys to montane, coniferous forests; 0-2500 m; Alta., B.C., Sask.; Ariz., Calif., Colo., Idaho, Miss., Mont., Nev., Oreg., Utah, Wash., Wyo.

Montia linearis is a highly uniform species.