Cactus garden. Cacti and succulent plants are plants that have evolved in arid environments. They have tissues adapted to minimise water loss. Cactus leaves are reduced to narrow spines, and the plant surface is covered in a thick, waxy outer layer. Many cacti and succulents also have a means of storing water. The large, tall cacti are from the Trichocereus genus. The broad-leaved plants at bottom centre are succulents called swan's neck agaves (Agave attenuata). Photographed in a garden in Monaco, France.