From the Greek melon, the melon, and kaktos, spiny plant, a reference to the globular shape of this cactus (Cactaceae). These are greenhouse succulent perennials globular to barrel-shaped, with 9-20 ribs. The majority have short spines, but some species have spines 6 inches long. At the top of the plant a ‘cephalium’ forms to protect the flower buds—it is composed of matted wool or fine hair, and has given rise to the popular name turk’s cap cactus. They are very tender plants.
M. amoenus, globular, with acute ribs and strong spines, small pink, Colombia. M. broadwayi, globular to barrel-shaped, stout awl-shaped spines, small pink to pale purple flowers, West Indies. M. maxonii, globular, reddish spines, pink and white flowers, Guatemala. M. townsendii, globular, sometimes forming groups, pink flowers, Peru. M. zuccarinii, sometimes branches at the base, awl-shaped spines, small pink flowers, Venezuela.
Use compost with few added nutrients with 1 part extra sand, grit and broken brick. They should be repotted every three or four years in March, and kept in the sunniest position in the greenhouse. Water well during hot weather, but only when thehas dried out, between March and September; for the rest of the year do not water at all.
Some species, especially those from the West Indies, require the addition of a very small quantity of common salt to the water. During the winter the temperature should not drop below 60 °F (16°C), but in the summer they will stand the highest temperatures, provided there is adequate ventilation
Propagate by seed sown in a good seed compost in March, kept moist and shaded in a temperature of 75 °F (24°C). They are very slow-growing, but the seedlings can be hastened by grafting them on to a Trichocereus stock.