Oreocereus trollii
Family: Cactaceae​
​Common Names: old man of the mountain
Origin: Oreocereus trollii originates from the arid mountains of South Bolivia and Northern Argentina, 2,900 to 4,300 meters above sea level.
Description: The old man of the mountain is a shrubby cactus that forms clumping, columnar stems that lie horizontally over time. The ribbed form is covered in fine white hairs, and possesses formidable, orange to red spines. From mid spring to mid summer, mature plants will produce violet semi-tubular flowers and globose fruits.
  • Interesting Features:
    • The thick white wool enveloping the stems evolved to protect the cacti from night frosts and strong sunlight within its native habitat.
    • Oreocereus trollii has received the RHS Award of Garden Merit.
  • Uses: Because of its drought tolerance and unique appearance, the old man of the mountain has been used extensively in cultivation for xeriscape, rock, and other desert gardens.

Cultivation and Care:
  • Watering: Low
    • Water only when dry, providing more irrigation in summer.
    • However, suspend watering in winter, as this cacti is very sensitive to rot under humid and cold conditions.
  • Soil: O. trollii faces the best growth in rich, acidic soil (5.0 – 6.5). To prevent root rot, it is imperative that soil be well draining. Feed monthly with a balanced, liquid fertilizer.
  • Lighting: Provide full sun to partial shade, but protect from strong afternoon sunlight.
  • Propagation: Cacti can be propagated through offsets, seed, and woody stem cuttings. For cuttings, allow to completely dry and cultivate in summer. Seed can be collected from over-ripe fruits, with March being the best time to plant.
  • Cold Tolerance: 0°F, USDA hardiness zones 7a to 11.
  • Special Accommodations: Although cold tolerant for short periods, ​O. trollii should be cultivated indoors during excessive periods of cold.
    • Plant in a plastic pot, as clay will dry too quickly, and repot every year with fresh soil.

Sources:
  1. Llifle Encyclopedia of Cacti
  2. Plant Desert
  3. Shoot Gardening
  4. Dave’s Garden
  5. Garden Tags
  6. Garden
  7. The Palm Tree Company
  8. Cactus Limon