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blue myrtle-cactus (Myrtillocactus geometrizans)

Myrtillocactus geometrizans is a spiny, succulent, evergreen, perennial columnar cactus with a shrub- to tree-like habit; mature plants branch heavily and often form a candelabra-like crown.

LightMyrtillocactus geometrizans takes full sun and can be grown in full sun or bright, strong light.
WaterWater moderately during the growing period, supplying water normally from mid-spring to early autumn and keeping it nearly dry at other times; water again after the surface of the growing medium has dried.
HumidityIt is generally reported to prefer low humidity.
TemperatureSources differ on minimum temperature, with the few available sources indicating about 0 °C. Sources also differ on its hardiness classification. It is generally reported to be frost tender; keep above freezing, and it i
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Overview

Myrtillocactus geometrizans is a spiny, succulent, evergreen, perennial columnar cactus with a shrub- to tree-like habit; mature plants branch heavily and often form a candelabra-like crown.

Origin and habitat

Sources differ on its native range, describing Myrtillocactus geometrizans as endemic to Mexico and widespread there, primarily in central regions with extensions northward and into some southern states. It occurs in xeric scrub, tropical or dry deciduous forest, and less often grassland, generally in arid to semi-arid settings; some sites have gypsum or limestone soils with relatively high salinity. Its native environment is predominantly arid to semi-arid and warm; a single source also reports a distinct rainy period and describes the regional temperature and rainfall.

Characteristics

Sources differ, but mature height is reported at about 400–500 cm, while the few sources for mature spread differ and report about 0–500 cm. It grows quickly. Sources differ in their descriptions of the small flowers, which range from white or creamy white to greenish white or yellowish white and last about a day or less. Sources differ on flowering season and on fruit descriptions; the berries are described as dark red, dark purple, purple-blue to blue when ripe, with juicy flesh that some sources describe as sweet.

Light

Myrtillocactus geometrizans takes full sun and can be grown in full sun or bright, strong light.

Watering

Water moderately during the growing period, supplying water normally from mid-spring to early autumn and keeping it nearly dry at other times; water again after the surface of the growing medium has dried.

Humidity and airflow

It is generally reported to prefer low humidity.

Temperature and dormancy

Sources differ on minimum temperature, with the few available sources indicating about 0 °C. Sources also differ on its hardiness classification. It is generally reported to be frost tender; keep above freezing, and it is generally reported as not frost tolerant. It rests cool in winter with a little water; a single specialist source reports a cold minimum of about -4 °C, so sources are few.

Growing medium and mounting

Use a well-drained cactus medium; horticultural sources support loamy or sandy soils under acidic, neutral, or alkaline conditions. It needs a fast-draining mix.

Feeding

A single source reports that a low-nitrogen fertilizer can be applied monthly from mid-spring to early autumn.

Propagation

Myrtillocactus geometrizans can be propagated by seed or cuttings; stem cuttings are suited to summer or hot weather and should be kept relatively dry while rooting.

Common problems

It is reported to be susceptible to mealybugs and generally to have no notable disease problems. It is sensitive to frost and freezing, and exposure to freezing conditions should be avoided in cold regions. Maintain good drainage, allow the growing medium to dry thoroughly after watering, and limit water in winter.

Identification

Sources differ in the details, but the stems are described as blue-green to blue-gray with a whitish bloom and conspicuous ribs; mature plants branch profusely into a candelabra-like form, and each areole may bear from a few to several spines.

Photos

Myrtillocactus geometrizans
📷 Juan Carlos Fonseca Mata · CC BY-SA 4.0 · source
Myrtillocactus geometrizans
📷 Alexis López Hernández, some rights reserved (CC BY), upload · CC BY · source

Sources