Echinocereus roemeri is a densely caespitose cactus specie, often growing in large colonies up to 1 m in diameter, containing sometimes 200 or more simple stems. Echinocereus roemeri is a cactus with both hermaphroditic (bisexual) and dioecious (male and female) forms of flowers on different plants. Male flower shows pollen-filled anthers surrounding the base of the stigma lobes, while functional female flowers from different plants show reduced filaments and empty anther sacs held below the stigma lobes.
Common Names: White-spined Claret-cup Cactus, Golden Rainbow Hedgehog
Stems:Dark green, ovoid to cylindrical, 20-40 cm tall, 3 to 5 in diameter .
Ribs: 8 to 11 somewhat tuberculed.
Spines: Acicular, mostly undifferentiated between radials and centrals;
Radial spines: (5-)8-12(-20) round in cross-section, 1-2 cm long, usually whitish.
Central spines: 0 to 4, longer and stouter somewhat angular in cross-section, the main one often flattened, up to 7.5 cm long; usually yellowish or whitish, but sometimes reddish or blackish.
Flowers: Borne below the stems apex, oftem unisexual (plants dioecious) broad Infundibuliform, orange-red, crimson or (rarely) pinkish, 3-10 cm long, up to 8 cm in diameter, perianth-segment obtuse or retuse, stigma with 7 or 8 lobes, usually greenish, areoles on flower, and ovary felted, bearing short white bristly spines.
Blooming season: Spring
Fruits: Globose, becoming red, with spines falling away.
Some of the information in this description has been found at desert-tropicals.com, llifle.com and cactus-art.biz