Description: G. megalothele
is a (usually) solitary
geophytic cactus with great white double flowers and a (usually)
five ribbed appearance with yellow spines.
Stem: Flattened or
globular, grey-green to olive green, 5-6 cm in diameter,
up to 5 cm tall, but in cultivation it can become 7-8 cm high (or
more) over the years.
Radial spines: Stout 5-7 up to 12, but usually less in young
plants, flattened against the body.
Central spines: Usually absent, or 1 erected one.
Flowers: Are some of the largest in this genus, often growing
larger than the plant!, 6 up to 7 cm long and wide,
pure white and double petaled.