Cactus leaves have become a lot smaller so they don't lose so much water; most have shrunk to spines or hairs but some have disappeared altogether! The stems are green to make food for the plant ...

I have a few tips on their water needs ... This Quiabentia verticillata from Bolivia,which is a cactus but has fleshy leaves attached to its spines, dropped all its leaves last year, its first ...

This means that they have special features that help ... Image caption, The spines of a cactus are much better than flat leaves at preventing water being lost from the plant.