Oreocereus celsianus
Family: Cactaceae​
​Common Names: old man of the Andes
Origin: Oreocereus celsianus originates from the semi-arid Andean region, on rocky slopes with eastern and northern orientation. The species is widespread in its native environment, growing in Argentina, Bolivia, and Peru from altitudes of 2,600 to 4,000 meters above sea level. 
Description: The old man of the Andes is a ribbed, columnar cactus that forms colonies up to 3 m tall in the wild, but around 2 m in domestication. The stems are thickly covered with woolly white hair, sprouting from the head of the cacti and decreasing toward the base. Over time, basal branching may occur, with new growth either prostrate or ascending. Mature cacti bloom in spring, developing tubular flowers that are cerise to magenta in color.
  • Interesting Features:
    • Its extensive coat of hair protects O. celsianus against the ultraviolet rays of the sun, as well as providing “antifreeze” chemicals within the sap, allowing the cacti to be frost and sunburn resistant.
    • O. celsianus has received the Royal Horticultural Society’s Award of Garden Merit for outstanding value in cultivation.
  • Uses: The showy flowers attract both bees and Patagona gigas, the largest species of hummingbird.
    • Additionally, the fruits of Oreocereus species are edible and are often consumed by people within its natural habitat.

Cultivation and Care:
  • Watering: Low
    • Moderate water can be provided in summer, provided that soil is allowed to completely dry in between waterings.
    • Do not irrigate on humid or overcast days, and keep as dry as possible during the winter, especially in cold locations.
  • Soil: Plant O. celsianus in a rich, fast draining cactus soil, adding pumice or perlite in a 1:1 ratio with soil to improve drainage. Ensure that a pH between 6.1 and 7.8 is maintained.
  • Lighting: Provide direct sunlight for most of the day, if possible. Greater light exposure will encourage a dense coat of hair and the development of flowers. However, protect from very hot summer days.
  • Propagation: The old man of the Andes cactus can be propagated both from seed and woody stem cuttings. However, due to the slowness of growth, it is not recommended to propagate from seed.
    • For cuttings, allow to fully callous before planting directly into soil.
  • Cold Tolerance: 10°F, down to 5°F if kept completely dry. USDA hardiness zones 8a to 10b.
  • Special Accommodations: O. celsianus should be protected from heatwaves and strong frosts, and requires strong sun.
    • Repot when necessary, as often as once a year, and fertilize monthly from spring to summer for the best growth.

Sources:
  1. Llifle Encyclopedia of Cacti
  2. Mountain Crest Gardens
  3. Succulents Network
  4. Garden
  5. Planted Shack
  6. Dave’s Garden
  7. Plant Lust
  8. Garden Tags
  9. Kykeon Plants
  10. JSTOR
See this species in the Mark Dimmitt Desert Plant Conservatory Virtual tour