– Melocactus (2008)

By Nikki Murdick (July 2008)

Melocactus is an unusual cactus that was first brought to Europe by Christopher Columbus. At that time it was called the melon-thistle, as Europeans thought it was the fruit of a giant thistle. It was described in Theodor Tabernaemontanus’ Book of Herbs, published in 1588. The plant was also described by cactus experts Link and Otto, who wrote about cactus during the 1700s and 1800s.

Melocacti are prominently ribbed, medium- to dark-green cacti that can reach a maximum of 18 inches in diameter and 36 inches in height. The skin color varies from species to species with various shades of green, blue and gray. The spines on the ribs of the cacti are usually curved inward toward the plant, although some are very long-spined. The tiny short-lived flowers, which are borne on the cephalium in spring and summer, are pink, red or purple.

When young, melocacti look much like any other solitary, globular cacti. It is when they reach maturity that they are easily recognized by their distinctive cephaliums. The cephalium is a dense, woolly growth produced at the top of the stem. This may occur from age 7 to 20 years of age. Once the cephalium develops, the plant itself grows very little, if at all.

Melocacti require shallow containers and loose, very well-drained soil. They are very sensitive to cool temperatures and must be kept warm at all times. They like humid weather and grow well in our summers. Once they are acclimatized, they can be grown in full sun. During the winter, they can be kept in the house, as they need to be kept warm and watered lightly during that period.

There are approximately 40 species of Melocactus. Found in the Caribbean Islands, Mexico and Central and South America, they are considered endangered in the wild.