This is a very distinctive plant even without flowers. The "sunny" Rebutia is particularly attractive, thanks to its tiny silver-white pectinate spines and brown areoles, a gem!!!
Origin and Habitat: Bolivia
Rebutia heliosa (Aylostera heliosa) is a small cactus with heads densely covered covered in brown areoles with white short pectinate spines, giving it a silvery appearance. This odd cactus is unmistakable and very distinctive. It is considered by many one of the nicest species.
Cultivation and Propagation: These plants come from mountainous areas, so like bright light, cool and dry conditions in the winter; this is important for the flowers as well as for their health. Without this cool winter period (0-10° C) they normally won't get many buds. They have a thick taproot and are of difficult cultivation and rot prone because of a great sensitivity to the excess of watering, not easy to get to any large size on their own roots really a challenge to grow into a large clump. They are commonly grafted to avoid root problems and to make easier to grow. Sun Exposure: Suited for sunny-brightly exposure; can tolerate light shade.
Cultural Practices: Suited for airy exposures. Needs deep pot and good drainage to accommodate its tap root.
It is very cold resistant as low as to -10° C or less for short periods of time. It is a fine plant for a rock garden or container, contrasts well with agaves, yuccas, and low-growing flowering plants.
Pests & diseases: Rebutia heliosa is especially prone to root rot, therefore, underpot in a smaller container filled with very porous compost.
Propagation: Cutting as it branches freely from the base; Also can be grown from seeds or graft.

Some of the information in this description has been found at desert-tropicals.com, llifle.com and cactus-art.biz

Bloom Season	Summers to spring
Botanical Name	Rebutia heliosa
Common Name	Aylostera heliosa
Dormancy	Winter
Family	Cactaceae
Flower Color	Green
Growth Habit	Rosette shape
Mature Size	1 m
Native Area	Bolivia
Resistance	5 (10)° C