Dioecious or gynoecious (staminate plants in equal frequency as pistillates or none in populations, respectively). Plants 5-20 cm (stems sometimes stipitate-glandular, especially in dioecious diploids). Stolons 2-7 cm (woolly). Basal leaves 1-3-nerved, spatulate, 15-20 × 4-6 mm, tips mucronate, abaxial faces gray-tomentose, adaxial green-glabrous (margins white woolly). Cauline leaves linear, 7-16 mm, (apices acute) not flagged. Heads 5-8 in corymbiform arrays. Involucres: staminate 4.5-7 mm; pistillate 5-7(-9) mm. Phyllaries (relatively wide), distally white (apices acuminate). Corollas: staminate 3-5 mm; pistillate 4.5-6.5 mm. Cypselae 0.8-2 mm, glabrous or slightly papillate; pappi: staminate 3.5-5.5 mm; pistillate 5.5-8.5 mm. 2n = 28, 56, 84, 112, 140. Flowering summer. Moist forests, slopes and tops of ridges under Douglas fir, ponderosa pine, Engelmann spruce or Gambel oaks, openings in the forests; 1500-2900 m; Ariz., Calif., Colo., N.Mex., Tex.; Mexico (Chihuahua, Coahuila). Antennaria marginata has rims of white hairs (from the abaxial faces) around its adaxially glabrous leaves. It has both dioecious and gynoecious populations and cytotypes ranging from diploid to decaploid (R. J. Bayer and G. L. Stebbins 1987). It is probably a primary sexual progenitor of the A. parvifolia polyploid complex; the two taxa sometimes overlap morphologically; they differ in induments of basal leaves. Antennaria marginata may also be a contributor to the parentage of the A. howellii and A. rosea agamic complexes.

Plant: Perennial, often matted; stems 15-18 cm; stolons horizontal, 2-7 cm Leaves: alternate, entire, basal 15-20 mm, spoon-shaped, 1-veined, green above with white-woolly margins, gray-tomentose below; cauline 7-16 mm, linear INFLORESCENCE: heads 5-8, discoid or disciform, in cyme-like clusters; involucre 5-7 mm, sparsely hairy at base; phyllaries wide, tips acuminate, upper part white; receptacle naked Flowers: Staminate flowers 2-5 mm; corollas 4.5-6.5 mm, white, yellow, or red; pappus bristle tips generally enlarged; Pistillate flowers 2-10 mm; corollas 4.5-6.5 mm, barely lobed, white, yellow or red Fruit: achene, 0.8-2 mm, papillate; pappus 5.5-8.5 mm. bristles many, soft, weakly barbed Misc: Dry woods; ± 2150 m.