What Is The Classification Of Cactus?

Cactus plants are just fascinating. But most of us don’t know much about them. What is the classification of cactus plants? How many types of cactus plants are there in the world? Let’s find out.

Every living organism can be classified into different scientific groups it belongs to depending on its physical characteristics. The highest category is the kingdom while the lowest classification is the species. As you move from the top (kingdom) to the bottom (species) of the classification tree, the characteristics of the organism become more specific and defined. 

So, what is the classification of cactus? Cacti belong to Kingdom Plantae, Phylum Tracheophyta, Division Anthophyta, and Class Magnoliopsida.  These succulents belong to Subclass Caryophyllidae, Order Caryophyllales and Family Cactaceae. There are approximately 150 genera in the entire Cactaceae family, but they are generally divided into three subgroups: Opunitieae, Pereskieae, and Cactoidea. There are over 2000 different cacti species that fall into two main categories, namely Opuntias and Cactoids.

In this article, we cover everything you need to know about the classification of the cactus plant. We shall also highlight some of the critical features of a cactus plant and how these succulents interact with human beings. So, let us get started.

Understanding Cactus Etymology

The word cactus is derived from the Greek word Kaktos which means a spiny thistle, possibly the cardoon. The Greek term was modified to cactus in 1753.

Although cactus is a common term, there is some dispute over the word’s proper plural form. If we stick to the original Greek word (Kaktos), the correct plural in English would be “cactoi” or “cactuses.”

However, as a word in Botanical Latin, distinct from Classical Latin, the term cactus is forced to follow the standard Latin rules for pluralization to become “cacti.” In fact, “cacti” has become the standard pluralization for cactus in English.

Regardless, the term “cactus” is commonly used as both singular and plural in many parts of the world and is cited as both singular and plural by the Random House Unabridged Dictionary.

What Are the Main Elements of a cactus Plant Used in Its Classification?

Every living organism has its unique features that usually play a critical role in its classification. Here are the main features of a cactus plant that determine its classification:

1. Stem

Cacti plants have succulent stems that store water. The stem can be smooth or covered with small bumps known as tubercles. Other stems can be ribbed in shape. The ribs become more visible when the cactus is short of water but invisible when the plant has stored plenty of water.

The stems of cacti plants are mostly some shade of green because they contain chlorophyll, which is needed during photosynthesis.

They also have stomata that open and close at different times of the day to allow the passage of gases. Some cacti plants have waxy stems.

2. Leaves

Most cacti plants don’t have real leaves. It is one of the features that help them survive in deserts. Instead of leaves, they have spines that protect them from predators.

The stems are modified to perform photosynthesis. However, some cacti species have tree-like leaves, which may be short-lived or permanent. It all depends on where the cactus grows naturally.

Although most cacti do not have actual leaves, some species might steel feature tree-like leaves.

3. Areoles

Areoles are fur-like areas on the stem of the cactus plant from which flowers and spines grow. Areoles may be oval, circular, separate, or entirely separate but still connected to each other.

The multicellular hairs of the areoles give them a brownish or yellowish woolly/fur-like appearance. They produce spines and flowers in most cacti species and then become inactive after that.

4. Roots

Most cacti plants have fine roots that spread out around the base of the succulent to absorb water.  Most of them grow shallow roots that are only a few inches below the ground surface. However, some species have a taproot that is much larger than the body to support the taller column-like cactus.

 Tree climbers (a special type of cacti plants) usually have unique roots produced along the stem whenever the cactus comes across something that it can cling or root onto.

5. Flowers

Cacti flowers differ from species to species.  The flowers can either grow in clusters or as single blooms. Their colors range from white to red, yellow, and magenta. 

Some cacti species bloom in spring, while others bloom in summer.

Various cacti species produce different colored flowers, typically in spring or summer.

6. Spines

You need to keep in mind that cactus spines aren’t thorns. Spines are modified leaves, while thorns are mostly modified branches. Spines grow from the areoles and are still present even in cacti species with leaves.

Some cacti species, especially the tree-living ones, only grow spines when they are still young. Cacti spines differ in thickness and may appear bristle-like or hair-like. They can be curved, hooked, or straight.

Some cacti species have minute spines that shed quite easily and can cause severe pain and irritation when they penetrate your skin.

Cacti spines and thorns can cause severe pain and skin irritation.

The Six Classifications of a Cactus

Below are the six classifications of a typical cactus plant:

1. Kingdom

Kingdom is the highest classification group. We only have two Kingdoms, namely Plantae and Animalia.  Since cactus is a plant, it automatically becomes a member of the Kingdom Plantae. On the other hand, all animals are members of Kingdom Animalia.

2. Phylum and Division

Cacti plants belong to the Phylum Tracheophyta because they are vascular plants. These succulents belong to the Division Anthophyta because they are flowering plants. The other name for flowering plants is angiosperms.

3. Class and Subclass

These desert plants are part of the Class Magnoliopsida and Subclass Caryophyllidae. They belong to Class Magnoliopsida because they are dicots.  All plants categorized in Class Magnoliopsida and subclass Caryophyllidae are insect-pollinated, and their seeds have two cotyledons.

4. Order and Family

Cacti plants belong to the Order Caryophyllales and the Family Cactaceae. Caryophyllales is a relatively large group of approximately 26 families of flowering plants with over 12,500 different species.

This includes the succulent plant families Cactaceae (cacti), Aizoaceae, Portulacaceae( Purslanes), Didieraceae and the carnivorous plant families Nepenthes and Droseraceae.

Order Caryophyllales also features essential horticultural and agricultural crops such as bougainvillea, Caryophyllaceae, spinach, rhubarb, and beet.

5. Genus

There are over 150 genera in the extensive Cactaceae family. The different genera are further classified into three tribes or subgroups: Opunitieae, Pereskieae, and Cactoidea.

Almost all cacti plants fall into the Cactoidea subgroup. Two genera, namely the Maihueniahe Persicae and Pereskia, make up the subgroup.

Cacti plants in these genera mainly have woody stems and semi-deciduous leaves. Their areolas are also wolly and spiny at the leaf axils.  These cacti plants produce flowers and fleshy fruits.

The Opunitieae mainly comprises the prickly pear varieties, including Pterocactus, Tacinga, Quiabentia, and Pereskiopsis.  These cacti varieties usually have fleshy branches, and their areolas have fine hairs. Their fruits are seedy, and the leaves are cylindrical or flat.

6. Species

There are over 2000 different cacti species that fall into two main groups, namely Opuntias and Cactoids.

The common features to both categories include fleshy stems modified to perform photosynthesis, small absent leaves and flowers with ovaries buried in a receptacle. Cacti plants in both categories also possess areoles and develop shallow roots.

The other cacti species that don’t belong to the two categories mentioned above fall in any of the two remaining categories: Pereskia and Maihuenia.

Mature cacti plants that fall in any of these species usually have woody barks that highly resemble trees. They also have true leaves that perform photosynthesis, and their flower ovaries are not sunken in a receptacle.

Those that fall into the Maihuenia category tend to have small globular bodies with tiny leaves at the top. However, some members of this group look like normal trees.

Cacti Plants and Humans

Human beings have been growing cacti plants as houseplants for many years. Some people use cacti fruits and nopales as food and herbal medicine.

The prickly pear is one of the commonly cultivated cacti. Both its stems and fruits are edible in many parts of the world. The cactus is native to Mexico and the southwestern parts of the United States, where it is highly cherished and used for food and medicinal use.

The prickly pear juice is used to relieve skin rashes and wound pains. In Africa and parts of Australia, the prickly pear is used as cattle food and a natural thorn fence to protect cattle from predators and thieves.

Prickly pear is one of the most popular cactus plants producing edible fruit and pads.

Other cacti species have also been useful to human beings. For instance, the giant Saguaro Cactus bears edible fruit while the Peyote produces a juice with a hallucinogenic effect mostly used in Native American religious ceremonies.

Final Thoughts

Cactus is a flowering plant with over 150 genera and approximately 2,000 species. Classification of cactus, just like any other living organism, depends on its physical traits.

Although most of these succulents are native to North and South America, we have a few species spread worldwide. Mexico remains the leading country with the highest number of cacti species.

While some cactus species inhabit tropical and subtropical areas, most of them grow in deserts and are well adapted to surviving in the harsh environment.

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