– Melocactus (2005)

By Mike Hellmann (February 2005)

I am fascinated and intrigued by most all cacti, yet the Melocactus genus is my favorite. While most of the cacti genera have much to offer, the melocacti have a certain stature and noble character that one only has to see to appreciate.

This appeal was noticed by European explorers over 500 years ago, as melocactus were the first cactus brought to Europe by Christopher Columbus. Instantly called Melon Thistle, it was described in 1588 by J. Theodor Tabernaemontanus in his famous Book of Herbs.

Melocacti are spherical in shape with a few species becoming cylindrical with age. Mostly solitary, the plant bodies seldom offset. Skin color varies from species to species, with various shades of green, blue and gray. Spines are usually short and curved inward toward the plant, although a few are very long-spined, such as M. erythranthus and M. macrocanthus.

A few melos mature at 3 to 4 inches across, yet most are larger, some spanning over 12 inches. Maturity is reached with the development of the cephalium, which appears as a crown of fuzzy or bristly growth at the apical growing tip of the plants. Usually solitary, the cephalium may divide into two or more heads.

Flowers emerge from the cephalium and usually appear quite small. These exquisite flowers are vividly colored and emerge throughout the growing season. Because of this beautiful cephalium, the most common name for this group of cacti is Turk’s Cap. The seed pods that soon develop can be plucked out very easily. When melos reach this cephalium stage, body growth nearly ceases.

Considering how long the plants have been in cultivation, they are still reputed to be hard to grow. While they have a few issues with being grown in pots, if one understands their few cultural needs, this reputation can be cautiously sidestepped.

First of all, these cacti are endemic to primarily coastal areas of Central America, Brazil and Peru. Almost all the Peruvian species live more inland. This fact tells us that they need year-round warmth to do their best.

This near-equatorial climate has no real winter or low temperatures. It is just hot and humid. The soil in which melos grow consists of more organic matter than that in the soil of their desert counterparts. A more uniform soil moisture is also the norm. This tropical biotype mirrors our summers. Heat and humidity are cherished by melos.

Most melos grow in full-sun locations. If we position the plants in full sun (acclimate first!), they will show their best color, shape and spination. Maintaining uniform soil moisture in a porous soil will promote good growth. Melos will take more fertilizer than other globular cacti and benefit from it if the other above criteria are met.

Winter here in the Midwest mandates a few changes in the tropical treatment of our melos. The winter months are a bit more challenging than the summer growing season. Position the melos, if possible, on a sunny windowsill with minimum room temperatures around 60 to 70 degrees. Make the top of the soil dry between waterings and make sure the plants do not sit in a saucer of water when finished. Problems can develop with cool temps and wet roots.

There are some big advantages to growing melos for hobbyists. They love our summer climate and are well adjusted to take the winter in our normal living quarters. Due to our ability to almost duplicate the climate from which they originated, melos need not be as difficult to grow as they are reputed to be.

The cephaliums of melocacti are beautiful, draw attention and offer beauty year-round, even when not studded with flowers. Two smaller species, M. matanzanus and M. violaceus, cephalate at a size of less than 4 inches and thus are less expensive to acquire compared to some of the larger ones. Most are inexpensive prior to developing a cephalium.

There are a few challenges that you also need to be aware of. Melos seem to be very conducive to hosting mealy bugs and scales. These pests are easy to control if detected early. Watch for them, especially in the folds of the plant body and just at the base of the cephalium. Use a contact insecticide after first moving the plant out of full sun to avoid phytotoxic damage to the plant body.

Melos may lose roots if the climate is not to their liking, especially if they are grown too dry, too wet or too cool. They seem to re-root as easily as they lose roots, so if you encounter this, clean up the base of the plant, let it dry and then re-root in fresh, moist medium. Cephalated plants seem to put all their resources and strength into procreation instead of vegetative or root growth. These mature plants are tougher to re-root and establish than those that are not yet sexually mature.

Seedlings are easy to grow. Seeds are readily available from most mature plants in the form of red or pink fruits full of small black seeds. Squeeze the seeds out of the fruit, let dry and sew as you would most other cacti. It has been noted that seedlings grafted onto other stock do not grow any faster than those on their own roots.

Sources:
Cacti and Succulents – Gunther Andersohn
Cactus Lexicon – Curt Backeberg