Herbs, matted, dioecious, (0.5-)1-2 × 3-8 dm, sparsely tomentose. Stems: caudex spreading; aerial flowering stems erect, slender, solid, not fistulose, arising at nodes of caudex branches and at distal nodes of short, nonflowering aerial branches, (0.5-)1-2 dm, sparsely tomentose. Leaves in loose basal rosettes; petiole 0.7-3 cm, lanate to tomentose; blade elliptic to ovate, (0.5-)1-2 × 0.5-1.5 cm, densely grayish-lanate on both surfaces, margins entire, plane. Inflorescences: staminate plants capitate, rarely umbellate, 1-2 × 1-2 cm; pistillate plants capitate, rarely umbellate, 1-4 × 1-4 cm; branches tomentose to floccose; bracts 4-6, semileaflike to leaflike, 3-5 × 1-3 mm. Involucres 1 per node or 2-3 per cluster, turbinate to turbinate-campanulate, tomentose; staminate plants 2.5-3 × 3-4 mm, teeth 5-6, erect, 1.5-2 mm; pistillate plants 3-4 × 3-4 mm, teeth 4-5, erect, 2.5-3.5 mm. Flowers: perianth yellow to brownish yellow, glabrous; staminate flowers 2-3 mm, including 0.5-0.7 mm stipelike base; pistillate flowers (3.5-)5-8 mm, including 0.5-0.8 mm stipelike base; tepals monomorphic, oblanceolate to obovate; stamens exserted, 1-2 mm; filaments pilose proximally. Achenes light brown to brown, 3-4 mm, glabrous except for sparsely pubescent beak. Flowering Jun-Sep. Gravelly serpentine flats and slopes, sagebrush communities, montane conifer woodlands; 1800-2400 m; Calif., Oreg. Eriogonum diclinum is found infrequently in the Siskiyou and Trinity mountains of northwest California (Siskiyou and Trinity counties) and southwest Oregon (Jackson and Josephine counties). The species approaches E. incanum in aspect, and reports of that species in Oregon were based on staminate specimens of E. diclinum.