Mammillaria is one of the most charming, collectible and instantly recognisable genera in the cactus family, Cactaceae. These ornamental plants are famous for their compact globose to cylindrical bodies, their neat spirals of nipple-like tubercles, and their remarkable variety of spines, which may be soft and feathery, glassy white, golden, hooked, bristly or densely interwoven. The genus name comes from the Latin mammilla, meaning “nipple,” a reference to the rounded tubercles that replace the ribs seen in many other cacti.

Native mainly from the central and south-western United States through Mexico, Central America, the Caribbean and into northern South America, Mammillaria reaches its greatest diversity in Mexico, where many species occupy highly localised habitats such as limestone slopes, rocky grasslands, desert scrub, thornveld-like shrublands and exposed gravel plains.

What makes Mammillaria so appealing to collectors is the way small plants can carry enormous character. Some species form solitary, jewel-like buttons tucked close to the soil; others cluster into cushions or mounds that become increasingly impressive with age. Flowers are usually produced from the axils between the tubercles and often form a beautiful ring or crown around the upper body of the plant. Depending on the species, blooms may be white, cream, yellow, pink, rose, magenta, red or occasionally greenish, followed by colourful club-shaped fruits that can add extra ornamental value.

For seed growers, Mammillaria is especially rewarding because many species germinate readily and develop into attractive miniature cacti while still young. Seed-grown plants also have strong conservation value with many ex-situ propagated plants in trade. Growing from seed is therefore not only fascinating, but also one of the most ethical ways to build a diverse cactus collection.

Mammillaria compressa commonly known as Mother of Hundreds is an easily clustering and easily flowered species. It is one of the largest of all the Mammillarias. Most plants will offset readily, and huge clumps can be produced in a very few years. It is a fast growing species which requires regular irrigation in summer but should be left to go dry between watering. For best results use a pot with good drainage and a very porous growing media. Keep it dry in winter and feed with a high potassium fertilizer in summer. It is quite frost resistant if kept dry, hardy as low as -12°C. Outdoors in the garden it thrives on full sun or afternoon shade, inside it needs bright light, and some direct sun. This is an easily clustering and easily flowered species. Most plants will offset readily, and clumps can be produced in a few years.