Plants annual, with slender tap-root. Stems erect, branched from base, branches ascending (fas-tigiate), 10-50 cm, pubescent with stiff, gland-tipped, patent or slightly reflexed hairs with broadened base, pubescence shorter than diam. of stem, soft wooly hairs absent; small axillary tufts of leaves absent. Leaves sessile; distal and mid-stem blades linear-lanceolate, 20-70 × 1.5-6 mm, apex acute to acuminate; proximal leaves shortly connate basally, blade narrowly oblanceolate, tending to be spatulate, pubescence short, stiff, patent, glandular. Inflorescences very lax, making up at least 1/ 2 height of plant, 3-45-flowered cymes; bracts, linear-lanceolate, 2-22 mm, herbaceous, glandular-pubescent. Pedicels erect to spreading, bent distally, slender, 5-20 mm, 1-5 times as long as sepals, usually longer than capsules, glandular-pubescent. Flowers: sepals narrowly lanceolate, 4-5 mm, margins narrow (narrower than herbaceous center), apex sharply acute to acuminate, glandular-hispid, hairs shorter than sepal tips; petals oblanceolate, 4-5 mm, ± equaling sepals, apex 2-fid; stamens 10; styles 5. Capsules cylindric, curved, (5-)7-10(-11) mm, ca. 2 times as long as sepals; teeth 10, erect to slightly spreading, margins convolute. Seeds golden brown, 0.5-0.8 mm diam., coarsely tuberculate. 2n = 36.
Flowering summer. Sandy canyons and washes, open rocky and sandy places and dry pine woods in arid mountains; 1900-3000 m; Ariz., N.Mex.
Until recently Cerastium fastigiatum was included in C. nutans but it is readily separable by its bushy, ascending habit, shorter pubescence, long, narrow leaves, and smaller capsule. It can be very similar to forms of C. brachypodum but differs from that species in its longer pedicels, narrowly acute leaves, glandular pubescence on the stems, and much more branched (fastigiate) habit. From C. nutans var. obtectum it differs in its very narrow sepals, narrowly lanceolate leaves, and smaller capsule.