Royal Botanic Gardens Kew - Kew Gardeners Guide to Growing Cacti and Succulents

This impressive display was created for an open day in the Tropical Nursery at the Royal Botanic Gardens, Kew.

A succulent plant can be defined as any plant that has the ability to store water within its tissues, and the word succulent is derived from the Latin word sucus (juice), which refers to this characteristic. Where succulents store water can differ between species: some do so in their leaves; others in their stems; while yet more conserve water in their roots or sometimes in a combination of these places. Based on this characteristic, succulents can be very loosely divided into leaf succulents, stem succulents and root succulents.

The large majority of cacti are leafless stem succulents, with the exception of a few species that have semi-succulent leaves. As well as their succulent stems, some cacti also have a thick tuberous and succulent taproot to help them withstand dry periods.

The fact that all cacti store water means that they can all be classed as succulents. It is, however, worth remembering that, although cacti make up a large percentage of species considered succulent, not all succulents are cacti. Succulent Euphorbia, like cacti, are largely stem succulents and mostly leafless and some have succulent roots, too. Meanwhile, Aizoaceae and Crassulaceae are leaf succulents some with succulent stems and a few with succulent roots.

How succulent a species is largely depends on the environment in which it grows naturally. Succulents from harsher environments will have the ability to store more water and withstand longer periods of drought compared to species that grow in less arid environments.

Types of succulent plants

Leaf succulent

Gibbaeum dispar

Root succulent

Lophophora williamsii

Stem succulent

Euphorbia polygona var. horrida

Columnar cactus

Stenocereus thurberi

Epiphytic cactus

Rhipsalis spp.

Globular cactus

Echinocactus grusonii

Shrubby cactus

Opuntia microdasys

Trailing or clumping cactus

Cleistocactus winteri

Pieter van Wyk (SANParks) and Alex Summers (Cambridge University Botanic Garden) are seen here documenting succulents in the Richtersveld, South Africa.