Melocactus is a genus of especially aesthetically interesting cacti, distinguishable by their odd cephalium that protrudes from the top. The cephalium, a bristly collection of aureoles, is designed to produce flowers and fruit and grow up to 3 feet (90 cm) tall in some cases. Cephalia are red or white and form small pink flowers inside their mass, and their fruits are waxy and shaped like tubes.
Because of their appearance, Melocactus are popular cacti in cultivation. They are native to places with high temperatures and cannot tolerate frost. In the wild, they grow in various parts of the Caribbean, South America (especially Brazil), and Mexico. Notably, Melocactus cacti only develop their distinctive look once they reach maturity.
At the beginning of their lives, their appearance is typical of most cacti. They are globular and ribbed all over with aureoles. Plants develop the cephalium once they are fully developed, and once it begins growing, it will not stop until the plant itself dies. So they can be hard to identify before they have reached maturity. They can be a bit of a challenge due to some specificities in their care requirements. Melocactus are a better choice for experienced cactus growers. They are quite beautiful and extraordinary once fully grown.
Light: Lots and lots of bright sunlight is necessary for Melocactus to thrive.
Water: For cacti, they like fairly moist environments, so water regularly, especially during the growing season. Make sure not to let them sit in water to avoid rotting the roots.
Temperature: Warm tropical temperatures above 70 °F (21 °C). They cannot survive frost.
Soil: Most cactus potting mixes should work fine, ideally a well-draining mix with some organic material.
Fertilizer: Feed with a balanced, diluted fertilizer like a 20-20-20 mixed into their water during the growing season to help them develop.
These cacti are not difficult to propagate from seed. Sow the seeds in well-aerated soil that drains well, and make sure to soak them in warm water before you do. Then seal the new seeds to keep in heat and moisture, which will help them root. Their root systems will take a little while to develop, so do not overwater or overfeed them before they have the necessary equipment. Remember, always use fresh seeds.
Notably, Melocactus like to be fairly packed in, so keep them in a fairly small container that slightly constricts their roots. Repotting them at the beginning of the growing season is a good idea until they form cephalium, and the body stops growing. They should be repotted like other cacti, by lifting the root ball out all at once, cleaning it gently, and replacing it. Make sure not to replant in too large a container to avoid damaging the plant.
Melocactus are somewhat finicky cacti with unusual requirements. They should not be allowed to completely dry out, even in winter, and they can suffer from soil composition, drainage, water level, sun, and more difficult control factors. For that reason, these plants are best for growers who already have had some success cultivating cacti. Establish a balance with good aeration matched by ample water, good soil matched by good drainage, and these cacti should continue to grow. If they are grown successfully, their unusual tops make them among the more beautiful of desert cacti.