People often use the words cactus and succulent interchangeably, but they’re not exactly alike. If you know what makes these plants unique from one another, then it will be easier for you to transition into identifying them correctly!
Cactus is a type of succulent plant. What makes cacti very different from the rest of the other succulents are the 1)distinctive areoles, 2) unique, vibrant flowers, 3) absence of leaves, and 4) fruit formation. Cactus are often confused with other succulents because of their waxy fleshy stems and resistance to drought.
Do you also often mix up a cactus with some succulents? Are you in doubt if what you have is a cactus or another succulent? Don’t worry. I will simplify things for you, and let’s start by discussing what succulents and cacti are.
Succulent is a term used to describe any plant with exceptional water retention ability. Succulents store water in their thick fleshy leaves, stems, and roots to endure long drought.
In horticulture, succulent refers to a plant adapted and evolved to an arid environment to thrive. Succulents can be any plant from any scientific family that stores water in its fleshy tissues.
Succulent plants do not belong to a single plant family but several distinctive groups of plants. Biologists grouped them into several categories based on how they store water.
- Leaf succulents: succulent plants that store water within their broad and plumpy leaves. Examples of leaf succulents are Echeverias, Sedums, Haworthias, and Aloes.
- Stem succulents: succulents such as Euphorbias and Cacti have thick stems that stash water in preparation for drought.
- Caudiciform succulents: this group of succulents has caudex or an enlarged basal stem that serves as the reservoir to store water.
Are cacti succulents?
Cacti are succulents but belong to a separate plant category, the Cactaceae. They are considered succulents due to their ability to retain water and tolerate long periods of drought. But cacti possess several characteristics that make them distinct from all the other succulent plants. Although all cacti are succulents, not all succulents are cacti.
The plants from the Cactaceae family (cactus) are native to the American continents from Canada down through Central America and the West Indies, including the cold regions of Chile and Patagonia (South end of America). Mexico has a wide variety of cacti species. However, in the west American desert and Argentina’s mountain peak are discovered to have several cacti varieties.
On the other hand, many succulents are native to warmer regions such as Europe and the Far East, while others were found in south and east Africa. Succulents like sedums and sempervivums are native to colder areas and do well on rocky cliffs under the sun.
The distribution of cacti and succulents to other parts of the world began during the expedition in the 15th century. It is known that Christopher Columbus was the first to bring an Opuntia cactus to Europe. As several explorations were performed, cacti and succulents throughout the world were continually introduced and cultivated.
Several aspects that make cacti different from other succulents includes:
- Distinctive Areoles,
- Big vibrant flowers,
- Absence of leaves, and
- Fruit Formation
Cacti are often mistaken with other succulents because they have the same features. But if you pay close attention, you’ll be able to identify them correctly. Below are what makes cacti distinct.
Areoles are only present on cacti, and it is the key distinguishing feature of the Cactaceae family. Areoles are the small lumps and cushion-like structures on the stem of a cactus where the spines and glochid are located.
Other succulents may have spikes and thorns, but they cannot be classified as cacti if the spines are not growing on the areoles. Areoles are the defining features of a cactus that other succulents do not possess. Depending on the plants‘ condition, buds on the areole can transform into a flower or a new shoot.
Cacti have prominent beautiful blooms with unique physiological characteristics. Most cacti have large and showy flowers with several petals and stamens that come in different shapes and colors.
Other succulent plants have small and plain blooms, unlike intricate cactus flowers that are large and vibrant. Cactus flowers form from the areole of the plant and emerge as solitary. It starts as a bud and develops a bit of stem (although some produce a much longer stem), with tiny leaves around the stem tube. At the tip of the elongated stem is where the petals form.
Another distinguishing mark of a cactus are those modified leaves called spines that emerge from the areoles. Most cacti do not have leaves except for a few exceptions, such as the Pereskiopsis.
Other succulent groups have fleshy leaves where they store water and synthesize food. Cacti are different because they do not have leaves, but instead, they form spines that grow on the areoles. Spines do not retain water nor photosynthesize, but it helps reduce water loss by limiting airflow to the stem.
Some succulents have spines as well, but cactus spines are different. Cactus spines are separate organs. When you try to take them off, they will break without damaging the plant’s epidermis. In other succulents, spines grow directly from the epidermis and damages the skin if pulled.
When pollinated, some cactus flowers will turn into seed pods or fruits, which can be the source of seeds for propagation. Other cactus species have edible fruits.
Examples of cactus that bear edible fruits are Opuntias and Hylocereus. After the cactus bloomed and pollinated, it will form fruits that taste exceptionally delicious. Fruits are sometimes red or yellow when ripe.
The similarities of cacti and other succulents are their:
- Fleshy Stems
- Resistance to Drought
- Water Retention Ability
- Photosynthetic process
The reason why most people consider some succulents as cacti is because they possess identical qualities.
Some cacti are similar to other succulents because of the spines on the edges of their leaves and stems. The spikes help protect the plant from other animals that will try to devour them.
Euphorbia, Agave, Aloe, and Stapelia are some succulents that possess spines just like the cacti. Their thorny spines are the best defenses for survival and effectively shade them from the sun rays.
The spines of most cacti, euphorbias, and agave are long, rigid, and dangerous. While the Stapelias, Huernias, and Aloes have soft spines that won’t seriously hurt.
Cacti and other succulents have the same fleshy, thick stems that serve as storage space for water. Their waxy stems protect them from the intense sun and the risk of losing too much water.
Their stem tissues expand upon water absorption and retract if the plants utilize the water during the drought. It is their juicy stems that give them better resistance to dry seasons. The waxy epidermis that contains chlorophyll reflects sunlight minimizing the risk of sunburn. Succulents such as Lithops, Huernia, and Euphorbia are some succulents that have fleshy stems.
Most succulents have the same unique ability to survive dry spells for quite a while. They are tolerant to arid environments and tough enough to combat both drought and heat.
Cacti and other succulents have adapted to survive harsh weather conditions. They can go on for several days without water. Most succulents do well in hot weather too. Many plant enthusiasts like this characteristic of succulents because they will thrive with only minimal care.
It is natural for succulents to stash water in their system. Their shallow roots efficiently take in as much water as possible and store them in their stem tissues.
During the night, their stomata open up and absorb moisture from the air around them. Apart from storing water, succulents are also good at conserving water by keeping their stomata closed throughout the day to avoid transpiration.
Succulents, including cacti, perform a unique way of making food. All succulents perform Crassulacean Acid Metabolism (CAM) to synthesize food.
Cacti and all other succulents only manufacture food at night. During this time, the minute opening on their stems called stomata opens up to take in CO2 and absorb water from the surrounding. When the sun peeks in, the stomata start to close and perform photosynthesis. Through this process, the risk of water loss is reduced.
Apart from differentiating cacti from other succulents, here is the list of common cacti and succulents that might help with classification.
|OTHER COMMON SUCCULENTS
|Echinocactus grusonii ‘Golden Barrel ’
|Echeveria imbricata ‘Rose Cabbage’
|Opuntia microdasys ‘Bunny Ears’
|Euphorbia milii ‘Crown of Thorns’
|Carnegiea gigantea ‘Saguaro Cactus’
|Aeonium Arboreum ‘Tree Aeonium’
|Astrophytum asterias ‘Sand Dollar’
|Schlumbergera truncata ‘Thanksgiving Cactus’
|Haworthia fasciata ‘Zebra’
|Gymnocalycium mihanovichii ‘Chin Cactus’
|Senecio rowleyanus ‘String of Pearls’
|Mammillaria spinosissima ‘Red-Head’
|Notocactus scopa ‘Silver Ball’
|Melocactus matanzanus ‘Turk’s Cap’
|Adenium obesum ‘Desert Rose’
|Ferocactus glaucescens ‘Blue Barrel’
|Corpuscularia lehmannii ‘Ice Plant’
Aloe Vera belongs to the succulent plant group under the Asphodelaceae family. Like all succulents, aloe vera leaves are thick and juicy. They store water in their long broad leaves for long-term use. Aloe vera is not a cactus.
Aloe vera plants can thrive in a relatively parched environment like cacti and other succulents. Its waxy leaves with teeth on the edges are the key features that play an essential role in survival.
Some succulents, such as Euphorbia, Aloe, and Pachypodium, look so close to cacti, that sometimes it is hard to tell them apart. But the rule of thumb when identifying a cactus is to look for the areole. Without the areole, you cannot call the plant a cactus.
I will show you below why people confuse these succulents with cacti.
Euphorbiaceae or spurge are succulents that look precisely like a cactus, but it is not. There are many species of these plants, and the majority of them have erect stems covered with spines. By visually observing the plant, one can say that it belongs to the Cactaceae. Although spines are similar, they do not develop from the areoles.
When you inspect the plant closely, you will convince yourself that the plant is not a cactus. If you poke the stem of a euphorbia, you can see a white milky secretion that contains latex. Cacti do not have that liquid in their body. Another point is that the flower of euphorbia is much smaller compared with the blooms of the cactus.
Pachypodium is another succulent plant that bears spines. It is arborescent like a cactus, meaning it can grow tall like a tree. Its trunk is full of spikes and holds water as well.
However, Pachypodium produces leaves on the top of its trunk, and the spines do not grow on areoles. In short, Pachypodium is not a cactus.
Aloes is another succulent plant with spines and drought-tolerant. But Aloes is by far different from cacti. It is just another succulent that is mistaken as a cactus.
Gardeners must know what type of succulents they are growing to provide the proper growth requirements for that particular plant. Succulents have different characteristics and different needs.
Others love a bit more water, while others prefer infrequent water. By identifying your succulent plant, you will know if it can be toxic to your kids and pets. Or you can distinguish which one loves sunlight and which one is shade-tolerant. Recognizing your plant is essential to make sure that your plant and family will not be in danger.
This article is packed with information about similarities and differences between cacti and other succulent plants. I hope these pieces of information have helped you open your understanding and will be able to distinguish whatever succulent plants you have in your collections.
- Succulents are any plant capable of storing water in its thick stems, leaves, or roots.
- Cacti are different from other succulents due to their areoles, flowers, fruit formation, and the absence of leaves.
- Succulents and cacti are alike based on their spines, fleshy stems, water storage, drought tolerance, and photosynthesis.
- ‘Common Adaptations of Succulents,” by Emily Rose Alworth, The Botanic Garden of Smith College
- “Vegetative Terminology,” Palomar College
- “Cactus Versus Succulent,” by Susan Croissant, University of California
- “Families of the Caryophyllales: Cactaceae,” University of Illinois
- “Cactaceae,” University of Illinois
- “Plant Growth Process: Transpiration, Photosynthesis, Respiration,” University of Nebraska
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