Stem tubercles 8-24 mm. Radial spines usually 8-15 per areole. Flowers 2.5-7.5 cm diam. Fruits 12.5-26 mm diam. Flowering summer; fruiting fall. Semidesert grasslands, plains grasslands, pinyon-juniper woodlands, gentle slopes, mesas, valleys, usually on alluvial or igneous substrates; 1200-2100(-3000) m; Ariz., N.Mex., Tex. Mammillaria wrightii var. wrightii is sometimes sympatric with M. viridiflora, but usually occupies deeper soils.