isa a distinctive large cactus, minimally spined with a green
ball-shaped body. Usually solitary or slowly clustering as they age.
Smooth, globoid, shiny green, up to 20(-25) cm in diameter.
Ribs: 5-6 cm wide, rounded, somewhat acute, deeply furrowed.
Spines: Few (usually 5 of which one pointing downward others to
the sides) , yellowish white, sparse, straight to slightly curved,
definite and very irregular, up to 3 cm long.
Flowers: White, pale pink,
pink or pale purplish up to 11 cm long and in diameter.
Fruit: Ovoid, blue-green.
G. horstii are very similar if not identical, both have very
similar great pink flowers and the same (usually) five ribbed
appearance, and good, yellow spines.