Myrtillocactus
Myrtillocactus is a small genus of shrubby to tree-like columnar cacti from Mexico and Central America, instantly recognisable by their frosted blue-green stems that branch and re-branch into broad candelabra-shaped shrubs. The genus is a favourite with growers for two reasons: the plants are fast, forgiving and beautifully coloured, and they produce clusters of small edible berries that in Mexico are gathered and sold under the name garambullo. It is also one of the most common cacti offered as monstrose and crested novelties.
Description
Members of Myrtillocactus begin as a single stem but soon branch freely, building up a many-armed, candelabra-like shrub or small tree that can reach several metres tall in habitat. The stems are typically a striking waxy blue to blue-green — the bloom rubs off to reveal greener tissue beneath — and are divided into a modest number of prominent ribs. Spines are short and comparatively sparse for a columnar cactus, often with a single longer central spine and a few short radials, so the overall impression is of smooth, ghostly-blue architecture rather than fierce armament.
The flowers are small, greenish-white to cream, and unusually for cacti several may emerge from a single areole. They are followed by the feature that gives the genus its name (Myrtillus, "little myrtle-berry"): small round fruits, often blue-purple when ripe, sweet and edible, resembling tiny bramble-berries. In their native range these garambullos are a genuine seasonal harvest, eaten fresh or dried.
Distribution
The genus is native to Mexico and extends south into Guatemala, where the plants grow in warm, seasonally dry scrub, thornforest and rocky slopes. They are creatures of heat and good drainage, tolerating long dry spells and flushing into growth with the rains. The best known and most widely grown species, Myrtillocactus geometrizans, is common across the arid centre and north of Mexico.
Notable species
- Myrtillocactus geometrizans — the "blue candelabra" or garambullo; by far the most cultivated species and the usual host stock and source of monstrose and crested forms.
- Myrtillocactus cochal — the "cochal", a shrubbier species from Baja California.
- Myrtillocactus schenckii — a taller, more tree-like species from southern Mexico.
Cultivation
Myrtillocactus is among the easier and faster columnar cacti to grow, which is a large part of its popularity. Give the plants bright light to develop the best blue colour, a very free-draining, mostly mineral mix, and warmth. Water generously through the active growing season, always allowing the mix to dry between waterings, then keep the plants dry and above freezing through winter — they are frost-tender and rot easily if left cold and wet. See Watering and Repotting for general technique.
Their vigour makes them excellent grafting stock: many growers use a length of M. geometrizans as a rootstock to speed up slow or delicate seedlings and to support the crested and variegated novelties that cannot support themselves. See Grafting for method.
Hobby and cultivar notes
Myrtillocactus geometrizans is one of the plants most often encountered as a monstrose form — best known under the Japanese cultivar name 'Fukurokuryuzinboku' (the "breast cactus") — in which the ribs and areoles proliferate into knobbly, boulder-like growth utterly unlike the tidy wild plant. Crested (cristate) fan-shaped specimens are also common. Because these mutant forms grow oddly and often weakly, they are frequently produced and sold as grafts. All of these novelties share the same easy care as the parent species; when grown on their own roots they simply want the warmth, light and sharp drainage described above.
See also
- Myrtillocactus geometrizans — the flagship species
- Grafting · Soil and potting mix · Watering · Propagation — seed · Propagation — cuttings
- Pests and diseases