Few cacti are as popular as mammillarias. For one thing they include a vast number of species and secondly they can be relied on to flower. The, furthermore, form a delightful wreath on the crown and are followed by carmine red or bright red club-shaped fruits.
The name of the genus is derived from the word mammilla, meaning nipple. This may be encountered in literature spelled in two ways: Mammillaria or Mamillaria. The first is the correct spelling (not in Latin, but botanically) for that is the officially recognized name by which it was first described.
The approximately 300 species described to date are distributed over an area extending from the southern states of America through Central America, including the West Indies, to Colombia.
The body of Mammillaria bombycina is about 20 cm (8 in) high and 6 cm (2-½ in) across. It is covered with conical areoles from which grow two types of spines: radial spines and central spines. The first number 30 to 40, are white, about 0.2 to 1 cm (1/8 to ½ in) long and radiate outwards; the central spines, usually 2 to 4, are darker, attain a length of 2 cm (1 in) or more and terminate in a hook. The flowers, forming a wreath near the crown, are about 1.5 cm (¾ in) across and coloured pale carmine, often with a darker centre. The plant’s attractiveness is enhanced by the thick white wool growing from the axils of the areoles. Mammillaria bombycina is native to Mexico.
Many mammillarias tolerate very low temperatures in winter if kept dry and so can be successfully grown in a window glasshouse placed outside the window. The most suitable species for this purpose are M. centricirrha and M. hidalgensis.