(This plant comes in a 3.5" pot. You will receive a very similar plant to the one in the picture. It may or may not be blooming at the time of your purchase. The plant is shipped in its pot to prevent any damage to the roots).
This is a globular, dark-green, grey-green to green cactus that can grow up 7 to 10" in diameter and up to 3" tall. The genus name "Gymnocalycium" comes from the Greek for "naked calyx" referring to the flower buds bearing no hair or spines. The flowers are some of the largest in this genus, often growing larger than the plant.
Recommended temperature zone: USDA: 9-11
Frost tolerance: Hardy to 18°F (-8°C)
Minimum avg. temperature: 50°F (10°C)
Sun exposure: Light shade
Watering needs: Summer grower, water regularly in summer, keep rather dry in winter
Blooming habits: White flower, 3" in diameter (7 cm)
Some of the information in this description has been found at desert-tropicals.com, llifle.com and cactus-art.biz