Plants perennial; taproot stout; caudex simple or branched, woody, bearing tufts of basal leaves. Stems erect, simple proximal to inflorescence, 30-60 cm, softly pubescent and stipitate-glandular. Leaves 2 per node; basal ± petiolate, petiole ciliate, blade oblanceolate, spatulate, 5-12 cm × 7-20 mm, apex acute, short-pubescent on both surfaces; cauline in 3(-4) pairs, reduced distally, blade oblanceolate to lanceolate. Inflorescences open, narrow, with ascending branches, 9-25-flowered, bracteate, pubescent and stipitate-glandular; bracts narrowly lanceolate, ciliate. Pedicels 1/ 2-3 times longer than calyx. Flowers: calyx prominently 10-veined, tubular in flower and fruit, umbilicate, somewhat constricted around carpophore, 15-38 × 3-6 mm, papery, sparsely pubescent and stipitate-glandular, veins parallel, green, with pale commissures, lobes 5, broadly ovate, 2-4 mm, scarious around green midrib; corolla pink or rose red (rarely white), clawed, claw equaling calyx, limb oblong, fanlike, deeply 4-lobed, lobes divergent, lanceolate (rarely with only 2 lobes, each with small lateral tooth), (7-)10-20 mm, appendages linear, 2-4 mm; stamens exserted, shorter than petals; stigmas 3, shorter than petals. Capsules narrowly ovate-elliptic, longer than calyx, opening by 6 recurved teeth; carpophore 4-18 mm. Seeds grayish brown, reniform, 1-1.5 mm, verrucate. 2n = 48.

Flowering summer. Grassy openings in chaparral, coniferous forests, and woodlands; 700-2300 m; Calif.

The long, tubular calyx and the proportionally long carpophore of Silene occidentalis are remarkable. Plants with the longest calyx tubes (more than 30 mm) have been referred to subsp. longistipitata and appear to be confined to Butte County. Calyx length varies greatly, however, and it is doubtful whether it is a justifiable basis for taxonomic recognition. The deeply lobed pink petals, together with its habit, give S. occidentalis a superficial resemblance to the European S. flos-cuculi, which occurs as an introduction on both sides of the North American continent.