Oreocereus celsianus aka Old Man Of The Andes

Oreocereus celsianus is a perennial cactus called old man of the Andes. It belongs to the cactus family, Cactaceae. Its native range runs from Peru through Bolivia to northern Argentina. It grows on sheltered, rocky slopes high in the Andes. These sites drain well and receive little rain. Winters are cold and dry, while summers bring warmth.

This cactus forms clumps of upright stems that branch near the base. RHS gives a garden height of 8–13 feet [2.5–4 metres]. Its spread reaches about 1.6–3.3 feet [0.5–1 metre]. Plants can take 10–20 years to reach full size. LLIFLE reports wild plants mostly below 6.6 feet [2 metres], with some exceeding 9.8 feet [3 metres]. The thick, round stems have green-grey to dark green skin. Each stem bears 9–25 ribs with small, rounded bumps. White hairs grow from large, oval areoles and hide much of the stem. The hair grows thickest near the tips; older bases become almost bare. Yellow to reddish-brown spines project through this coat.

Plants need several years before they start to flower. The blooms grow near the tops of the stems. They open by day and form curved tubes or narrow funnels. Their colour ranges from pale purple-pink to deep red. LLIFLE records spring flowering, while RHS places it in summer. Giant hummingbirds pollinate the flowers in the wild. The round, dry fruits turn yellow and split near the base. They hold several black seeds.

Grow this cactus in full sun with shelter from harsh weather. RHS recommends cactus compost under glass in a bright spot. Loam or sand suits it, with neutral to alkaline soil. Water during spring and summer, then keep it dry in other seasons. LLIFLE advises letting the soil dry between waterings. Feed monthly during the growing season, following the RHS guidance. RHS rates it H2, so frost-free culture is the safer approach. LLIFLE reports greater cold tolerance when plants stay very dry. Cold combined with damp can cause root rot.

Its tall stems and white coat suit a greenhouse or conservatory display. RHS also lists it as a houseplant needing little routine upkeep. It needs no pruning. Scale insects may attack, though RHS reports few disease problems. Grow new plants from seed in spring or summer, at 21°C.