Desert adaptations: old man cactus

Old man cactus (Espostoa superba)

Old man cacti (Espostoa superba) may look like they are wrapped up in cotton wool, but they are perfectly adapted to life high up in the Peruvian Andes.

Cacti habitat in the Andes mountains

These columnar cacti grow near the equator at altitudes up to 2500m, where high levels of ultraviolet (UV) radiation burn through the thin atmosphere.

Cacti adaptations

The bright white hairs reflect the sun’s intense UV rays like a pair of mirror sunglasses. They also insulate the plant, keeping its tissues cool in the hot Peruvian summer. The fluffy fibres are densest around the plant’s new growth point.

How to spot high altitude cacti

You can find other plants adapted for life at high altitudes in the display up the steps. Look for ‘hairy’ plants or plants with silver or white leaves.

How to spot low altitude cacti

Cacti that grow at lower altitudes have evolved different adaptations to suit their environments. Many are covered in a waxy coating, which reflects light and helps to prevent water loss. You can see a variety of ‘waxy’ plants nearby.