Cactus & Succulent Society
of New Zealand (CSSNZ)
What is a Cactus or Succulent?
What is succulence?
What exactly is a succulent plant?
The term succulent refers to a plant that has a capacity to store water in either stems, leaves or roots.
They generally come from low rainfall areas (so called "deserts") or what rain that does fall is not available
readily (e.g. Epiphytes high up in trees in tropical forests, or clinging to the rock face of a cliff) to the plant.
In order to survive in these extreme climates, many plants have evolved characteristics
whereby they store as much
water as possible while it is available, for use later in times of need and also conserve the water
they have stored.
As mentioned above succulents store water in at least one of three different places: roots, stems, or leaves:
Leaf succulents are instantly recognisable, shown by the thickness of the plants "leaves" e.g. Agaves, Aloes, Echeverias
Stem succulents have swollen stems or branches. Cacti and Euphorbias are two examples.
Root succulents accumulate water in underground storage organs called caudexes. The caudexes are sometimes partially exposed naturally. In cultivation, growers often raise caudexes above the soil for effect (or to prevent rotting).
Xerophytes are plants that are adapted to survive in dry climates, all succulents are basically xerophytes but not all xerophytes are succulents ... succulents have evolved special enlarged spongy tissue to store water ... other xerophytes have evolved means of conserving water loss e.g. hairs on leaves, reduced leaf size, thick leathery leaves - but are not succulents.
ALL Cacti are Succulents BUT NOT all succulents are cacti
The term "Cacti and other succulents" is often used and is similar to saying "Sheep and other farm animals".
All Cacti are classified as succulent plants, since they (all) exhibit (usually) stem (and root) succulence. The very
primitive cacti have leaves that are not usually succulent - a link in evolution.
Not all succulents are Cacti, however, because they do not all belong to the Cactaceae family. Similarly not all
farm animals are sheep.
The cactacae family is exclusive to the new world (Americas) and exclusively have areoles -
special organs from which
spines, flowers, new branches originate. Cacti comprise the single largest group of succulent plants
Succulent species are present in most plant families and spread throughout the world, and has evolved many times
independently in the families.
Among the plants usually referred to as 'The Other Succulents' are Euphorbias, a large, diverse group from the family Euphorbiaceae. Euphorbias are sometimes mistaken for Cacti, and similarities do exist amongst the two groups. Cacti, however, are 'New World' or from the Americas, whereas Euphorbias are found primarily in Africa or the 'Old World' and are not related to each other.
Large numbers of succulents are also found in the Mesembryanthemaceae, Crassulaceae, Agavacea, Portulacacea, Lillaceae and Ascelepiadaceae families to name but a few.
So there are approximately 10,000 separate species of plants, in nearly all plant families, that fall into the succulent category ... but they are not all Cacti - just 1600 of them !
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