Myrtillocactus is a small genus of columnar cacti in the family Cactaceae, order Caryophyllales, native to Mexico and extending into Guatemala. The genus comprises around four to eight species of tree-like or shrubby cacti, with the largest individuals reaching up to 5 metres (16 ft) in height. The stems are heavily branched and bear multiple ribs armed with spines; in mature specimens the candelabra-like branching habit is a distinctive feature of the Mexican scrubland landscape.
The genus is best known for Myrtillocactus geometrizans, commonly called the blue myrtle cactus or garambullo, which is widely cultivated as an ornamental and harvested for its small, edible, blueberry-like fruits. These purple-black berries give the genus its common name — "blueberry cactus" — and its scientific name, from the Latin myrtillus (myrtle or small blueberry) combined with cactus. The fruits are a traditional food source in central Mexico.
Plants flower in summer, producing relatively small whitish to greenish blooms. Monstrose and crested growth forms are known and are prized among cactus collectors. The genus also provides rootstock for grafting other cacti, as Myrtillocactus geometrizans in particular is a fast-growing and vigorous host.
The synonym Myrtillocereus Fric & Kreuz. (an orthographic variant) has been formally placed in synonymy with Myrtillocactus.
Etymology
The name Myrtillocactus derives from Latin myrtillus ("small myrtle" or "blueberry") combined with cactus, a direct reference to the edible, blueberry-like purple fruits produced by plants in this genus. The common name "blueberry cactus" translates the Latin literally.
Distribution
Myrtillocactus is native to Mexico and Guatemala, where it grows in arid and semi-arid scrublands and thornscrub vegetation. In Mexico, M. geometrizans is particularly characteristic of the Chihuahuan and Tehuacán-Cuicatlán desert regions.
Cultivation
Cuttings can be taken for propagation but must be rooted at sufficiently high temperatures — low temperatures prevent rooting. Established plants should be kept dry during winter and not allowed to drop below 8 °C (46 °F). The genus includes numerous monstrose and crested cultivar forms popular with collectors. Myrtillocactus geometrizans is widely used as grafting rootstock due to its vigorous, fast growth.
