When you think of succulents and cacti, most people assume that they are two separate but closely related groups of plants.
However, it is a bit more complicated than that. Succulents are a loose group of plants that have special adaptations for storing water in their stems, leaves, and roots.
They are not a separate plant family. There are succulents in no less than 60 different plant families. This makes succulents a very diverse group of closely related plants.
Cacti, on the other hand, are a family of plants defined in scientific taxonomy and plant classification. All cacti are succulents, but not all succulents are cacti.
Most people assume cacti are easy to spot because they have the thorns. That’s what I thought for years, but it turns out it’s not. Many plants other than cacti have thorns, both in the succulents group and in general. Also, many cacti have few or no thorns, so they can easily be misidentified if you’re not looking for the right things.
Turns out there’s a surefire way to tell if you’re looking at a cactus.
It all comes down to the areolas.
These are small, round, light- or dark-colored bumps on the surface of a cactus from which thorns, hairs, and flowers grow. If a succulent plant has areoles, it is a cactus. If you don’t have areolas, it can’t be a cactus
Interestingly, most cacti have no real branches or leaves. This is an adaptation to prevent water loss in the generally arid climates where most cacti live. The areoles are the cactus equivalent of tree branches and the spines are the leaves. However, there are branched cacti, such as the Saguaro cactus. In this case, the branches grow from the areoles.
Let’s move on to learn a little more about succulents.
Contents
What is a succulent?
The group of plants that make up the succulent category includes over 40 plant families, and some, if not most, of the plants in these families are succulents. Plant families with many succulent species include Agaves, Aloes, Cacti, Crassulas, Echeverias, Euphorbias, Kalanchos, Mesembs, Sedums, and Sempervivums.
The word “succulent” comes from the Latin word juicy, which means “full of juice”. Just look at aloe vera, which is famous for the slimy gel contained in the thick leaves of the plant. But the mere presence of a succulent substance does not confirm that a plant is succulent. In fact, there is no clear definition of what a succulent plant is. For example, there is much controversy as to whether yuccas belong to this group.
One way plant experts attempt to clarify the issue is that a plant must have fleshy leaves or stems that temporarily store water for use during dry spells to qualify as a succulent. This definition excludes storage organs such as roots, bulbs, rhizomes and corms. These features store food along with water and help the plant survive harsh conditions, such as excessive cold or heat and lack of light, rather than simply existing to help the plant survive periods of drought. .
The reason Because a plant stores water is also important. This is reflected in the common usage of the term “succulent” to refer to xerophytic succulents, drought-tolerant plants. This contrasts with halophyte succulents, which are plants that store water to survive in saline environments such as seashores, swamps, and marshes.
Gardeners also often exclude bromeliads, orchids, and palm-like cycads because the distinctive characteristics of these unique plants simply overshadow their succulent characteristics. Read my full article here for more information on succulent plant care.
Other Water Saving Properties of Succulents
The succulent, which is responsible for those fleshy stems and leaves, is perhaps the most obvious way to distinguish succulents from other types of plants, but it is only one of many mechanisms that these plants use to survive in dry conditions. Other water-holding properties that succulents may have include:
- Large concentrations of thick, sticky mucus.
- Surface features that protect the plant from water loss, such as a waxy coating and hairs or thorns that interrupt airflow around the plant and provide shade.
- Ribs or grooves that allow the plant to swell in water and then shrink during drought to reduce the area exposed to the sun.
- Compact, columnar or globular growth patterns that maximize the ratio of internal tissue to exposed surface to minimize water loss.
- Green stems that carry out photosynthesis.
- Shallow root system that can absorb small amounts of moisture that may occur on the soil surface.
- Crassulacean acid (CAM) metabolism, which allows the plant to reduce water loss by opening its pores only at night to absorb the carbon dioxide needed for photosynthesis.
What is a cactus?
A cactus is a flowering plant that belongs to the Cactaceae botanical family, which has over 1,700 known species, almost all of which are succulents. Plants of the cactus family are exclusively endemic to the Americas, with the sole exception of mistletoe cacti (rhipsalis), which also occur naturally in isolated areas of tropical Africa and Asia.
Most cactus plants are desert cacti, with the towering saguaro cactus (giant carnegie) of the Sonoran Desert is the most emblematic. But there are also jungle cacti, such as the Christmas cactus (schlumbergera), which bear little resemblance to cacti.
Cacti share many characteristics with other types of succulents and have certain tendencies that are typical but not exclusive to cacti. For example, most cacti are succulents with green, waxy, leafless stems that store water and perform photosynthesis. Sometimes the stems resemble leaves, such as Christmas cacti and prickly pears (opuntias), where the multiple stems of the plant consist of flattened segments or pads.
Other water-conserving succulent characteristics very typical of cacti include fluted or ribbed stems, columnar or globular growth patterns, shallow root systems, and numerous spines. And all cacti have CAM photosynthesis.
As mentioned above, the only unique characteristic of cacti, which other plants do not have, is a specialized structure at the base of the plant’s spines, as well as branches, leaves, and flowers. These features, called areoles, allow cacti to produce protective spines more efficiently, and they typically have multiple spines protruding from them.
Another way to identify a true cactus is to look for large, bold, colorful flowers that produce fruit. If a flowering succulent’s flowers are small or unimpressive, it’s probably not a cactus.
similar to a cactus
Euphorbia horrida – A succulent, but not a cactus
So if a cactus-like succulent has prickly spines, but they don’t come out of raised bumps or pads, you know it’s not a cactus. The main culprits in this cactus pretend play are the succulents in the Euphorbia sex. These plants evolved to fill arid climate niches in Africa similar to those in the Americas that gave rise to cacti. The succulent family Didiereaceae from Africa and Madagascar also bears many similarities to cacti.
If you’re having trouble identifying your succulent or deciding whether you have a succulent or a cactus on your hands, take a look at the amazing Cacti and Succulent Identification page on plants.com.
cactus care
Since cacti are succulents, you can follow general guidelines for succulents, keeping in mind that desert cacti need lots of direct sunlight, at least five to six hours a day. . They are accustomed to higher temperatures and lower humidity, although they adapt to most home environments as long as they receive adequate light.
Make sure the growing medium dries completely between waterings, and you usually don’t need to water them much during their winter dormancy.
Jungle cacti are a special case, requiring year-round indirect sunlight, higher humidity, and an evenly moist growing medium.