Myrtillocactus geometrizans
Family: Cactaceae​
​Common Name: blue myrtle-cactus
​Origin: The blue myrtle-cactus is endemic to numerous Mexican states, originating from tropical deciduous forests, xerophilous shrublands, and Chihuahuan grasslands. It has been recorded in over 267 localities, at 1,000 to 2,000 meters above sea level.
Description: Myrtillocactus geometrizans is a branching, tree-like cactus that develops a columnar to candelabra form. It will eventually create a spined architecture of stems, becoming woody with age, and the glaucous color will fade. Mature plants over two years old may form small greenish-white flowers during the spring, which will bloom for a single day before fading.
  • Interesting Features:
    • Popular in cultivation, the blue myrtle-cactus is fast growing, tolerant of most indoor conditions, and readily develops arms. As such, it is often used as an understock for weak or easily rotting cacti, especially in warmer climates.
  • Uses: The sweet red fruits produced by M. geometrizans have been an important staple for many Indigenous tribes, including the Apache, Papago, Tewa, and Ute. Additionally, the fruits are widely consumed in Mexico, where the berries are called garambullos.

Cultivation and Care:
  • Watering: Low
    • Irrigate only in summer, allowing the soil to completely dry in between waterings.
    • During the winter, water only when necessary to prevent the stem and branches from shriveling, and do not water overhead.
  • ​Soil: Plant in a well-draining cactus or succulent soil, adding gravel to aid drainage. Additionally, maintain a pH between 6.1 and 7.8.
  • Lighting: During the summer, site in a location that receives bright, direct sunlight. However, during the winter and when young, provide light shade and a cooler environment for the best growth.
  • Propagation: Myrtillocactus geometrizans can be propagated from seed as well as woody and softwood stem cuttings.
    • Plant cuttings during summer and do not water, as they require both heat and dry soil to root.
  • Cold Tolerance: 20°F, USDA hardiness zones 9a to 10b.
  • Special Accommodations: Protect from winter frost and extremely cold weather, especially in moist conditions.
    • Repot often (once a year) to allow the cacti room to root – but wear gloves when handling, to avoid damage by the sharp spines.
    • From spring to summer, feed monthly with a specialized cactus fertilizer to encourage growth.

Sources:
  1. University of Arizona Campus Arboretum
  2. Llifle Encyclopedia of Cacti
  3. Henry Shaw Cactus and Succulent Society
  4. Dave’s Garden
  5. Plant Care Today
  6. Cactus Art Nursery
  7. World of Succulents