Notocactus ottonis wigginsia nothohorstii
(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).
Parodia ottonis subs. horstii, best know as Notocactus horstii is a solitary or slowly clustering medium sized barrel cactus with many flowers in early spring.
This spherical cactus can grow up to 10 cm tall and 15 cm in diameter (but in cultivation plant tends to elongate and can grow up to 30 tall) the crown of the plant is covered in spiny white wool.
Recommended temperature zone: USDA: 9b-11
Sun exposure: Light shade
Origin: Southeastern South America
Growth habits: Slowly clumping when mature, up to 6" tall (15 cm), 6" in diameter (15 cm)
Watering needs: Regular water in summer. Keep rather dry in winter, rot easily if the substrate is wet and cold, tends to lose its roots in winter.
Flowers: yellow up to 1" in diameter.
Blooming season: Spring
Some of the information in this description has been found at desert-tropicals.com, llifle.com and cactus-art.biz