Herbs, annual, polygamodioecious; taproot slender. Stems arising directly from the root, spreading, solid, not fistulose or disarticulating into ringlike segments, sparsely glandular. Leaves usually quickly deciduous, basal, rosulate; petiole present; blade spatulate, margins entire. Inflorescences terminal, cymose; branches dichotomous, not brittle or disarticulating into segments, round, sparsely glandular; bracts 3–4, perfoliate and connate, spreading to recurved, usually 4-lobed proximally, 3–lobed distally, oblong to triangular, mucronate, sparsely glandular. Peduncles absent. Involucres 1 per node, tubular, turbinate, 4-angled, ventricose and sharply angled; teeth 4, mucronate. Flowers bisexual or unisexual, distal shorter one bisexual, proximal longer one pistillate, 2 per involucre; perianth bicolored, with floral tube yellow and lobes white to pink or rose, funnelform when open, tubular when closed, glabrous but densely papillate abaxially; tepals 6, connate 1/3 their length, monomorphic, 2-lobed apically; stamens 9; filaments free, glabrous; anthers maroon to red, oblong. Achenes exserted (bisexual) or included and aborted (pistillate), dark brown to black, not winged, 3-gonous, glabrous. Seeds: embryo curved. x = 19.
Systenotheca is the only member of Chorizanthineae that is polygamodioecious, a feature otherwise found in some members of Eriogonum (Eriogonineae). Among the eriogonoid genera, Systenotheca may be readily distinguished also by the 4-angled, 4-bracted, boxlike involucres. No pistillate flower has been observed to produce a mature achene.