Melocactus (2017)

By Rey Gonzalez (October 2017)

I remember being a child and visiting my grandmother’s house in Havana, Cuba, and every time I went there, I would spend a good amount of time contemplating her small cactus garden. Some stenocereus and leptocereus were taller than me back then, but two melocactus – M. matanzanus and M. harlowii – always caught my attention because of the “red hats” on top of them and the shape they had.

Melocactus is a small genus in the Cactaceae family. It is spread over a very large area, including the Caribbean Islands, Mexico, Central America and much of the north and central parts of South America. They have a globular shape with green stems covered with multiple ribs, which vary depending on the species (usually from 8 to 20). The spines are stout and curved, and can measure up to 2.5 inches in length.

This genus was very likely the first cactus seen by a European explorer, and certainly one of the first to be brought to Europe and successfully grown. They were known in English collections by the late 16th century.

Around 40 species have been described so far, with M. matanzanus the most widely grown species. Endemic to Cuba, my native country, this is one of my favorite globular cacti. M. matanzanus is among 13 other species in the genus.

One of the most fascinating things about a melocactus is that when it reaches maturity, a reddish-brown, bristle-coated structure of white wool called a cephalium appears at the apex of the plant. This adult body form differs so greatly from the juvenile that some people assume the plant is actually two separate genera grafted together.

The adult phase body is much narrower than that of the juvenile because both pith and cortex are narrower. The spine morphology also changes, with spines being shorter, straighter and so abundant that, combined with the close packing of the axillary buds, the adult surface looks like a brush with tightly packed bristles.

Although there is virtually no space between spines, somehow the axillary buds produce prodigious amounts of trichomes. The combination of trichomes and spines completely protects the adult surface from animals, sunlight, fungi, bacteria and even plant anatomists. I believe no other family of plants has members that undergo such a striking phase change.

The cephalium varies in color and height. Depending on the species, it can keep growing for many years. In some species, it can exceed the height of the plant body itself.

The cephalium is closely related to the reproduction of the plant, since it provides wonderful protection for developing flowers and fruits. As mentioned above, the cephalium has narrow shoots and closely packed nodes, which greatly reduces the “cost” of building each new axillary bud and thus, making it less “expensive” to produce a flower.

The overnight emergence of the flowers is dramatic. One can check a plant with no hint of flowers in the evening, then the next morning the bright pink/red/magenta flowers are completely open. The flowers usually last a few hours but open up in large groups at different times. After flowering, small bright red or pink, cylindrical fruits will originate. Each fruit contains plenty of seeds – the only means of propagation for the genus.

The positive benefits of having an apical cephalium are accompanied by some negatives consequences, as well. After reaching adulthood, not only is the total amount of photosynthetic tissue set, but the body of the plant stops growing and begins to age, since all of the energy goes into producing the cephalium, flowers and fruits.

In many countries of the Caribbean and Latin America, the genus is widely used in traditional medicine. In some regions of northeastern Brazil, the pulp of some Melocactus species is used to make an expectorant effective in the treatment of pertussis, amebiasis, catarrh, bronchitis, lung problems and worms.

In veterinary use, the pulp is mixed in water for chickens with chronic respiratory disease to help clear their throats. Juices, marmalades, candies, liquors and syrups are prepared from both the fruits and pulp of melos. Species such as M. bahiensis are used to make biscuits, coconut candy, pudding, cakes and candies, and thereby provide a source of income for rural communities.

Melocactus, along with many of the species that grow in the tropical or subtropical zones, must be kept in a warm environment, both day and night, all year long. A reason some growers avoid melocactus is the mistaken belief that the plants are particularly difficult to grow. Given the right temperatures and some attention to watering requirements, they are no more difficult to keep alive than most cacti.

All species of the genus grow in areas where there is moderate annual precipitation, but the rain falls in concentrated periods and drains away very quickly from the upper ground layer of gravel or rock. That’s why a very open and porous media is required to insure superior drainage and root aeration, but the roots must not be allowed to dry out too much.

If soil is so well drained that water simply runs through the roots and drains away instantly, there is no limit to how much water can be applied, but it has to be done regularly. On the other hand, if the soil is poorly drained and retains a quantity of water, watering must be very infrequent. Great care is needed to judge just when water can be reapplied.

Melocactus can’t stand frost, even for a very short time. If the air temperature drops below 50 degrees F, severe tissue damage or death can occur very quickly. At the other end of the scale, the exposed areas of plants growing in full sun can suffer scorching. Several populations of mature melocactus on some islands in the Caribbean can be found with brown or yellow sun-damaged epidermis on every plant.

I keep melocactus in the greenhouse, positioned where it gets plenty of morning and late afternoon sunlight. Another solution is to bring the plants indoors. Melocactus can make very good houseplants, if kept in a warm room with plenty of light.

I’ve been fascinated with this genus for a while and even more now that I’ve spent a good amount of time researching the plants online.

Once in a while, when I look at my M. matanzanus, childhood memories come to my mind. I got punctured plenty of times while being curious, but the plant also reminds me of where I come from, and especially my grandmother.

I cannot wait to own more species of this genus. They will occupy a special place in my greenhouse because they already have a special place in my heart.

Sources:
Cephalia: Juvenile/Adult Phase Chance in Cacti
Mauseth Research: James D. Mauseth, Section of Integrative Biology, University of Texas
http://www.sbs.utexas.edu/mauseth/researchoncacti/Cep halia.htm

The Genus Melocactus – Naturaleza Tropical
https://translate.google.com/translate?hl=en&sl=es&u=https://naturalezatropical.blogspot.com/2016/02/Melocactos-Melocactus.html&prev=search

How to Grow Melocactus Cacti – Jon Vanzile, The Spruce
https://www.thespruce.com/grow-melocactus-cacti- 1902965

Use and Knowledge of Cactaceae in Northeastern Brazil – Journal of Ethnobiology and Ethnomedicine
https://ethnobiomed.biomedcentral.com/articles/10.1186/ 1746-4269-9-62

Melocactus Care and Cultivation – George Thomson, Xochimanki
https://www.xochimanki.com/wp-content/uploads/2017/05/MELOCACTUS-care-and-cultivation-George-Thomson.pdf