Oreocereus trollii aka Old Man Of The Andes

Oreocereus trollii is a small, wool-covered cactus in the Cactaceae family. Its common names include old man of the Andes. It comes from southern Bolivia and northern Argentina. There it grows on very dry mountain slopes. Its range reaches heights of 9,500–14,100 feet [2,900–4,300 metres]. The thick coat shields its stems from strong sun. It also helps protect them from light night frosts.

Young stems start out round, then form short, thick columns. Branches grow from the base and can form clumps. Older shoots may lean sideways as they grow. Garden plants reach about 0.3–1.6 feet [0.1–0.5 metres] tall. RHS gives a spread of up to 0.33 feet [0.1 metres]. LLIFLE records taller stems reaching 3.3 feet [1 metre]. Each pale green stem has 15–25 low, knobbly ribs. The dense wool hides much of the stem beneath it.

This wool consists of fine radial spines, not true hairs. Their colour ranges from creamy white to grey. Strong central spines push out through the soft-looking coat. They can be yellow, orange, reddish orange, or brown. Dark tips mark these stout spines. Mature plants may flower during summer. The blooms are tube-shaped, in shades of pink to violet-red. They reach about 0.13 feet [0.04 metres] long. The fruits have a round shape.

Grow this cactus in full sun with shelter from wet cold. It needs a rich mix that drains very well. RHS suggests four parts cactus compost to one part limestone chips. Loam or sand suits it, with neutral or alkaline pH. Water during spring and summer, then let the mix dry fully. Keep it dry through the rest of the year. RHS advises a balanced liquid feed each month during active growth. Its H2 rating calls for protection from freezing in UK conditions.

This cactus suits pots, bright indoor spaces, conservatories, and greenhouses. RHS also lists it for patio containers and subtropical planting. Its compact shape fits small cactus collections. Plants take about five to ten years to reach full size. They need no pruning. Sow seed in spring at 21°C to raise new plants. Mealybugs may attack it, though RHS reports few disease problems. Cold, damp soil can cause rot, so winter dryness matters.