[4] Echinocereus poselgeri typically grows with several spreading shoots, forming a tuberous, dahlia-like rhizome.

A single, slightly flattened, dark central spine points toward the shoot tip and is up to 9 mm (0.35 in) long.

The dark green to brown fruits are egg-shaped and covered with persistent wool and thorns.

[5] Echinocereus poselgeri is growing in scrub valleys and hills of southern Texas, USA, and the Mexican states of Coahuila, Nuevo León, Tamaulipas, and San Luis Potosí, typically found at low elevations in sandy soil at elevations up to 1150 meters.

The specific epithet poselgeri honors Heinrich Poselger, a German doctor, chemist, and botanist who collected succulent plants in North America from 1849 to 1851.