Rebutia minuscula

Origin and Habitat: Northern Argentina
Common Names include:
ENGLISH: Violet Crown Cactus, Red crown Cactus, Fire Crown Cactus, White-haired Crown, Little Mouse, Orange Snowball

Description: Rebutia minuscula is a small clumping cactus species, widespread and extremely variable that has received numerous unnecessary names. Some of its variable forms don't look like the same species.
Flowers: Slender funnel-form, bright red to violet (but also yellow, orange or even white), to 4 cm long about 3,5 cm wide. Self fertile.
Remarks: Rebutia minuscula is quite variable. The differences concern the spination and flowers colour,

Cultivation and Propagation. It is easy to cultivate and recommended for beginners.
Growth rate: It is a slow growing but easily flowering species that will make clumps given the best conditions.
They are small container size plants and prefer deep pots and good drainage to accommodate their tap roots, but they rot prone, because of the sensitivity to excess of watering, not easy to get to any large size on their own roots (it's really a challenge to grow them into a large clump). They will occupy a small pot comfortably, and eventually remain a manageable sized house plant. It is better that they are repotted regularly. Repotting will increase the number and size of stems, and will increase the number of flowers produced. Repot yearly until they reach about 100 mm in size, then every two or three years will suffice.
Watering: It requires full sun or light shade and careful watering to keep plant compact, and maintain strong and dense spines and allow the pot to dry out between waterings. Keep dry in winter at a minimum temperature of 0°C. It tends to rot if too wet.

Hardiness: It is reputedly resistant to frost if kept on the dry side prior to, and during, cold weather and requires a winter rest period (hardy to -7° C, or less for short periods

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