Melocactus is a genus of cacti from the Cactaceae family. A more popular name for this group of cacti is melon cactus. There are 40 known species growing in deserts and the rocky terrains of tropical regions. The majority of these species can be found in the West Indies, northern South America, and Central America.
Melon cactus’ appearance takes after its name. Its stems have several ribs, which are round or melon-like in form. The needles follow a linear formation that runs along the cactus’ spines. As these cacti mature, a central floral-like cap called a cephalium grows on top of the stem. This part of the plant comes in colors of white, red, and orange and eventually bears small pink inconspicuous flowers at its apex.
The maximum height of these cacti is achieved once the cephalium grows. Cacti of this variety can be as short as 6 inches (15 cm) or as tall as 6 feet (1.8 m), inclusive of the length of their caps, which can grow up to 3 feet (0.9 m). Each species has different height limits that depend on the plant's individual environment. As most cacti are self-sufficient, only minimal attention is required to care for these ornamental plants. However, Melocactus plants are known for their slow pace of growth.
Azureus, or the Turk’s cap cactus, is one of the most commonly grown species in this genus. Its stem takes a dome shape, and its spines are attached to an apex that results in an asterisk formation. The off-white or reddish-brown cephalium can become extremely hard and thick as these cacti get older. Small light pink and red flowers can be observed growing on its cap, mostly during mid-summer. Potting or directly plotting them in the ground are options when cultivating these plants.
One popular ornamental cactus from the Melocactus genus is concinnus. Pink bulbs of flowers sprout around and on top of the cephalium, providing additional color to a monotonously green plant. Its stems turn into a bluish-green shade when fully matured, while the spines exhibit a reddish color with gray tips. Inedible purple fruits grow after the blossoms wither.
The roots of Melocactus plants remain shallowly grounded in the soil, and they generally grow in a horizontal direction. Pan-shaped containers best suit their roots’ manner of growth. Most species can take more than seven years before reaching full maturity. These are long-lasting ornamental plants that have a tendency to overcrowd when placed in pots. Prolonged exposure to extremely cold climates reduces the chance of the cacti’s survival.