Mammillaria guelzowiana

Mammillaria guelzowiana is another well known plant. It becomes more common in collections, and easily available as both plants and seeds from specialty cactus places.
Mammillaria guelzowiana is one of the most beautiful Mammillarias, with white 'hear' and red or yellow hooked centrals. Flowers are among the most beautiful in the genus as well, as you can judge yourself. The plant in the picture has flowers about 2-3 inches across and this is a form with larger flowers, sometimes called 'robustor'.
Mammillaria guelzowiana can reach flowering size of just over 1 inch in 1.5- 2 years from seed, if conditions are ideal. The pictured plant is about 10 years old from seed and overgrowing 7 inch/21 cm pot. The 'common' cactus culture suits this cactus well, and the pure mineral potting media is much preferred. In literature you may find notes of this plant been somewhat rot pron and gentle, something I do not see at all since I switched to mineral substrate. The flowering period here in California is more or less from May through September.