Mammillaria longiflora stampferi

Mammillaria longiflora stampferiMammillaria stampferi It is one of the more difficult species to grow long enough to produce clumps, but if grown correctly, it will reward the grower with generous displays of purple flowers; plants should be allowed to become crowded in their pot. Keep in shallow and smaller pot than normal. Must have very well draining potting soil. Watering Needs: Need regular water but do not water again until dry as it is specially sensitive to over watering.

Mammillaria stampferi

It is one of the more difficult species to grow long enough to produce clumps, but if grown correctly, it will reward the grower with generous displays of purple flowers; plants should be allowed to become crowded in their pot. Keep in shallow and smaller pot than normal. Must have very well draining potting soil.
Watering Needs: Need regular water but do not water again until dry as it is specially sensitive to over watering. Also, it is a species that is dormant in the winter and require very little water (maybe even none) during the cold months.
Frost Tolerance: Somewhat frost tolerant. Light frost protection required. Minimum of 5ºC for safe growing (but hardy up to -5°C or less.)
Sun Exposure: High levels of light are needed to flower and for good spine development. Can be sunburned if moved from shade/greenhouse into full sun too quickly. During the spring it may be able to take full sun until the heat arrives at the end of spring. In an area that has hot afternoon sun, it may be able to take full morning sun, but requires afternoon shade or afternoon light shade.

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