Mammillaria theresae

Mammillaria theresae is endemic to Durango Mexico. It is a small geophyte, usually single headed, This is a very distinctive little species. When it came into cultivation, it caused quite a sensation because of its peculiar long-tubed blossoms and the spines are very decorative: all radial, translucent white, plumose, forming little clumps, which needs to viewed under a lens to be appreciated. They look like furry little starfish. This species puts out a good amount of growth each year, but the individual stems seem to grow no larger, as the old growth tends to compact at the base. Plants bloom when still tiny (less than 2 cm tall), the bright magenta flowers of 5 cm in length often obscuring the plant. This will no doubt be one of the most talked about little cacti of all time.
Blossoming time: Mainly in may, but also sporadically though out summer.
Remarks: Cryptocarpic fruit: Mammillaria theresae is one of the few species of cactus with cryptocarpic fruits. That is, the fruit and seeds are produced and retained inside the stem of the plant. After the flower is finished and dropped off, the stem closes over the fruit and the fruit/seed gradually ripens within. The following years the fruit may remain within the body at the axil, or may protrude a bit. A thin membrane will be above the part where ripe seed can emerge. As the plant swells with the new growing season, the membrane fractures, and some seed from the past years can little by little drop down and germinate in the close proximity, forming small colonies. But usually the seeds remain within the plant body for several years or for the whole life cycle of the plant, and frequently they will be released only at the death of the plant after the disintegration of the old stem.
It is possible to collect fruit and seeds only by means of a thin pointed forceps. The seeds' vitality lasts for many years and moreover seeds contain inhibitors that preserve them from premature germination.

Cultivation and Propagation: like the other Mammillarias of the saboae group - is not the easiest of Mammillarias to grow and keep,. They need to be kept dry in winter.
Pot plants are quite wet-sensitive. Care must be taken with watering, and it needs good drainage. Water sparingly during the growing season; keep very dry in winter. But plants grown outdoors seems to tolerate easily the winter wetness. It has proved to be quite frost resistant and has demonstrated to survive safely outdoors under a cover of snow at a temperatures of -15° C. Sun Exposure: Full sun - Light shade.
Propagation: Seeds, cuttings or grafting. Germination of the seed can still prove to be a challenge.