All Cacti Are Succulents, but Not All Succulents Are Cacti
A cactus is a spiny desert plant. The defining feature is not the spines but a structure called an areole.
A cactus is a plant of the family Cactaceae, adapted to arid conditions. Botanists identify one by the *areole*, a small cushion from which spines, flowers and branches all grow. Many succulents have spines and none of them have areoles, which is how a euphorbia that looks exactly like a cactus is not one.
- A spiny desert plant. *A barrel cactus.*
- Cacti / cactuses — both plurals. *Rows of cacti.*
Word forms
| Form | Word | Example |
|---|---|---|
| Noun | cactus | A potted cactus. |
| Plural | cacti | Desert cacti. |
| Plural | cactuses | Two cactuses. |
| Related | succulent | A leafy succulent. |
| Part | areole | A spined areole. |
How it is used in a sentence
- Cacti are native to the Americas.With one debated exception in Africa.
- The areole is the defining feature.Botany.
- Cacti or cactuses are both correct.English allows either plural.
Cactus adaptations
- Spines — modified leaves, reducing water loss and deterring animals
- Areoles — the cushions unique to cacti
- Stem photosynthesis — the stem does the work leaves normally do
- Ribs — allow the plant to swell when water is available
- CAM photosynthesis — pores open at night to limit evaporation
From Latin *cactus*, from Greek *kaktos*, a spiny plant of Sicily — not the American plants the word now names. Linnaeus applied it in the eighteenth century.
Cacti or cactuses?
Both are correct. Cacti follows the Latin, cactuses the English pattern.
Is every spiny succulent a cactus?
No. Many euphorbias look identical but lack areoles and belong to a different family entirely.