Stems unbranched or in clusters, cylindric or elongate cylindric, 10-40(-45) × 5-9 cm; ribs 13-17, well developed, tubercles not evident on ribs. Spines dense, obscuring stems; radial spines 10-15(-18) per areole, white, straight, flat, 20-50 mm, glabrous; central spines 9-12 per areole, 5-8 hooked, others straight, terete to angled; abaxial and lateral central spines 6-8 per areole, red or reddish brown (rarely yellow), some hooked, (30-)56-100 × 0.7-1.2 mm; adaxial central spines usually 3 per areole, white, usually curved or twisted, flat, usually 37-86(-130) × 1.7-3.4 mm. Flowers with spicy, pungent odor, funnelform, 5-10 × 5-9 cm; outer tepals with greenish purple midstripes and rose-purple or magenta margins, cuneate-spatulate, usually 15-30 × 6-9 mm; inner tepals rose-purple to magenta (rarely white), largest tepals ovate-lanceolate, 24-45 × 9-12 mm; filaments greenish yellow; anthers cream; style grooved, not papillate. Fruits irregularly dehiscent at base, green, tan, or red, barrel-shaped, 22-50 × 12-25 mm, dry at maturity; scales few, white fringed. Seeds black, 2.7-3.7 × 2-2.5 mm, shiny; testa with fine, rounded papillae.

Flowering Apr-Jun. Rocky alluvial, often alkaline soils, Mojave desert scrub; 500-2500 m; Calif., Nev.

Sclerocactus polyancistrus is the only member of the genus that truly lacks papillae on the style, and its style possesses grooves, somewhat reminiscent of Ferocactus. It is easily recognized by its massive stem size (relative to other species of Sclerocactus), large flowers, and numerous hooked central spines (five to nine).