Mammillaria is one of the largest and most popular genera of cacti. They are known by many vernacular names such as nipple cactus, fishhook cactus, pincushion, and others. Because of their popularity, several hundred species have been described. A recent, fairly conservative classification by E. F. Anderson (2001. The Cactus Family. Timber Press) lists 171 species, most of which are native to Mexico, with some from Southwestern US and a few from South America and islands of the Caribbean. The name Mammillaria comes from the Latin word mamma, referring to the tubercles covering the plant body, and which, for a number of species, contain milky sap.

The first cacti to be grown in European gardens were brought back from the Americas by Columbus and other great explorers. Among the earliest to be grown were mammillarias and melocactuses. However, when Linnaeus published his plant classification, Species Plantarum in 1753, he placed all known cacti (then only 22) in the genus Cactus. Thus, the first Latin name for a mammillaria was Cactus mammillaris. Subsequently, following further exploration and the discovery of many more cacti in the Americas, the genus Mammillaria was created in 1812 by Adrian Haworth.

Mammillarias are small or medium sized plants, solitary or clumping with globose or short cylindrical or clumps of short cylindrical bodies. The Tubercles are set in spirals (mammillarias never have vertical ribs like most other cacti) and can be angled or cylindrical, longish and smooth. Spines are on the top of the tubercles (areole) and can be long or short, numerous or absent, hooked or straight, hair-like, bristle-like, and wool may be present or absent in the axils at the base of the tubercle.

The flowers are small or medium sized and set in rings around the top of the plant in the previous year's growth. Form and color are usually red, yellow, white, pinkish white, or pink with dark midveins. They usually open during the day and are born from a flowering areole set in the axils of the tubercles. The fruits are mostly bright red (sometimes yellow or white) and usually elongated or club-shaped.

In general, mammillarias are easy to grow. They do fine in a standard cactus soil mixture, strong light and moderate watering, especially during winter months.

A great internet site for pictures and information about mammillarias is: www.mammillarias.net/index.php