What is the difference between a cactus and a succulent?

What is the difference between a cactus and a succulent?

Next month’s meeting is all about succulents and cacti.  I thought it may be useful for you to know the difference between the two families.

People often use the terms succulents and cacti interchangeably, which is scientifically incorrect. Understanding the relation between the two will help properly distinguish them and help with identification.

Succulents are plants that store water in their stems, roots, and leaves. There are about 60 different plant families within the group of succulents, including aloe, haworthia, sedum, sempervivum, and of course, cacti. Cacti are fleshy plants that store water, making them part of this group. Therefore, all cacti are succulents.

What is the difference between a cactus and a succulent?
Spiny Succulent - Euphorbia tetragona
What is the difference between a cactus and a succulent?
Succulent without spines - Sempervivum tectorum

Cacti are simply a family, or sub-category within the group of plants collectively known as succulents. They range from tall and thin to short and round, and they usually do not have leaves or branches. In order for a succulent plant to be considered a cactus, the plant must have areoles. Areoles are small, round, cushion-like mounds of flesh where spines, hair, leaves, flowers, and more grow from the cactus. Areoles are only present on cacti, not all succulents.

What is the difference between a cactus and a succulent?
Spiny Cacti - Mammillaria backeberg
What is the difference between a cactus and a succulent?
Cacti without spines - Schlumbergera bridgesii

Some succulents are often mistaken for cacti because they have thorns or spines, but these characteristics do not automatically qualify a succulent as a cactus. The areoles are the key to distinguishing the two. Without areoles, the succulent cannot be a cactus.