Several groups of globose cacti occur in the Peruvian Andes, and Matucana is one of the most spectacular, often bearing red, hummingbird-pollinated flowers. I have had the good fortune of observing them in their habitat but have discovered that, like many other cacti, the species are extremely variable and have been confusing taxonomically. Fortunately, Matucana has been the subject of a thorough study by Rob Bregman (1996) of the University of Amsterdam.
His research has not solved all the problems, especially the question of whether some species have hybridized. Nonetheless, Bregman's work greatly clarifies the status of the genus. Nathaniel Britton and Joseph Rose described Matucana (type, M. haynei) in 1922 for a single species. The name of the genus is that of the Peruvian town near the type locality of M. haynei. Bregman (1996) recognized 19 species, 17 of which are accepted by the International Cactaceae Systematics Group (Hunt 1999a) and included here. Matucana is characterized as globose to short cylindrical, bearing bilaterally symmetrical flowers that are open during the day in summer.
The flowers may be of various colors, though most are red. The distinctive fruits are usually globose, about 1 cm (0.4 in) in diameter, and dehisce by three vertical slits. Matucana is closely related to Oreocereus, Oroya, and possibly Denmoza, each of the genera with different flowers, however. Myron Kimnach (1960) has suggested that Matucana belongs in Borzicactus, which the International Cactaceae Systematics Group places in Cleistocactus. The affinity of Matucana to other South American cacti remains somewhat unclear.
