What Is the Difference Between Cactus and Succulents?

People throw around the words cactus and succulents like they mean the same thing. Both are drought-resistant plants, with fleshy structures for water storage. So, what is the difference between cactus and succulents?

In the broadest sense, all cacti are succulents. However, not all succulents are cactus plants. While succulents grow all over the world, cacti are indigenous to the North and South Americas. Unlike succulents, they’ve developed unique adaptations like spines and areoles. Moreover, nearly all cacti don’t have leaves.

In this guide, we’ll walk you through the distinct features that set each other apart.

Cacti and Succulents

What Is a Cactus?

Cacti are succulent plants, and that much is clear. Cacti belong to the family Cactaceae, with many species living in immensely dry landscapes. The stems are either thick and herbaceous or woody and chlorophyll-rich.

Cacti have unconventional physical features that distinguish them from succulents. The most striking of their unique adaptations are their spines and areoles. These help them survive harsh, inhospitable conditions and dry climates.

Common Cactus Plants

Here are a few common cacti grown as ornamental plants:

  • Bunny ears cactus (Opuntia microdasys)
  • Old lady cactus (Mammillaria hahniana)
  • Star cactus (Astrophytum asteria)
  • Easter cactus (Hatiora gaertneri)
  • Queen of the Night (Epiphyllum oxypetalum)

What Are Succulents?

succulent

Unlike cacti, succulents are not a strict classification of plants. Instead, they refer to all plants that have thickened and fleshy tissues used mainly to store water.

This means that some species in a family or genus may be succulents, while others aren’t. In fact, more than 60 families have at least one species of succulent plant.

The following are predominantly succulent species:

  • Aizoaceae (fig-marigold family)
  • Cactaceae (cactus family)
  • Crassulaceae (stonecrop or orpine family)

Not only are succulents a sight for sore eyes, but they’re also low-maintenance. It’s no wonder they have a cult following among forgetful gardeners.

Common Succulents that Aren’t Cacti

These common succulents are prized houseplants:

  • Aloe vera (Aloe vera)
  • Jade plant (Crassula ovata)
  • Hens-and-chicks (Sempervivum tectorum)
  • Snake plant (Sansevieria trifasciata)
  • Whale’s tongue agave (Agave ovatifolia)

Related: What Size Pot for Succulents?

Differences Between Cactus and Succulents

Cacti and succulents are both flowering perennials. They can store moisture without losing it to evaporation, even under intense heat. Their root systems are shallow and spread widely, so that water can penetrate more easily.

Water engorges their plant tissues, which is why they have a thick and fleshy appearance. This makes both plants survive long periods of drought in deserts and semi-arid regions.

Despite these similarities, cacti differ from succulents in many aspects. Keep reading to learn more.

1.   Native Range

Succulents are present in all habitats across the world. Cacti, on the other hand, are native to the Americas, except for the Rhipsalis baccifera or mistletoe cacti.

Nearly all members of the genus Rhipsalis are South American natives. However, there have been sightings of the mistletoe cacti in East Africa, Madagascar, and Sri Lanka. How the species found their way across the Atlantic Ocean is subject to many theories.

Most cacti abound from the north of Alberta and British Columbia to the southernmost regions of Argentina and Chile. Mexico has the most abundant collection of cacti.

A few species thrive in the humid conditions of rainforests, usually in trees and on rock ledges. They’re often associated with aerial plants like orchids and bromeliads. Known as jungle cacti, their lack of spine makes them a highly unusual species.

A few examples of jungle cacti include:

  • Easter cactus (Hatiora gaertneri)
  • Thanksgiving cactus (Schlumbergera truncata)
  • Christmas cactus (Schlumbergera x buckleyi)

These plants are collectively known as ‘holiday cacti’ because of their festive flowers. The Schlumbergera varieties bloom around the holiday season, from November to January. Meanwhile, the Easter cactus produces flowers in springtime.

2.   Leaves

Succulents feature fleshy stems and leaves for storing water. Meanwhile, the overwhelming majority of cacti have lost their original leaves.

Out of 139 genera and around 2000 species, a few cacti groups break the mold and sprout leaves. A few species appear like normal shrubs or trees, and they bear leaves with midribs and flat blades or lamina on each side.

These few exceptions include all species of the following:

  • Leuenbergeria
  • Pereskia
  • Rhodococcus

Many species in the family Opuntia and the genus Maihuenia have visible leaves as well.

Read more: What Eats Succulents? 6 Likely Culprits

3.   Stems

Succulents carry out photosynthesis in both the leaves and stems. Because of the lack of leaves in most cacti, the process takes place in the stems instead, which are usually flat, but could also take on a leaf-like appearance in some plants.

Cacti stems are green, often with a brownish or bluish tint. They contain stomata, which are tiny pores typically found on leaves, to allow gas exchange. The thick and waxy skin or cuticle protects the plants from water loss and extreme temperatures.

In addition, the shape of the stem may be fluted or ribbed. This offers a quick way to determine whether a plant is dehydrated.

This special feature is more prominent when the plant is short of water. Conversely, when the stems become swollen with water, the ribs stay hidden in the background.

Spines

Most cacti have leafless stems that are covered with spines. Yet, don’t confuse spines with thorns. Spines are modified leaves, whereas thorns are more like shorty, prickly branches. While both spiky organs guard against herbivores and predators, spines serve a host of other functions.

Here’s a quick summary of the importance of spines in cacti:

  • Provides shade
  • Helps collect water
  • Traps air and regulates temperature
  • Aids in reproduction by sticking to passing animals
  • Reduces water loss during transpiration

Spines vary in color, size, number, shape, and hardness between species. One thing’s for sure, they make for a fascinating feature that adds to the cacti’s allure.

Take a look at some common descriptions used to identify spines:

  • Needle-like (e.g. Eve’s needle cactus or Austrocylindropuntia subulata)
  • Bristle-like (e.g. bristle brush cactus or Mammillaria pilcayensis)
  • Claw-like (e.g. eagle claw cactus or Echinocactus horizonthalonius)
  • Hairy (e.g. Hairy Roger Cactus or Opuntia engelmannii)
  • Hooked (e.g. fishhook cactus of genera Mammillaria and Sclerocactus)
  • Flattened (e.g. paper-spined cactus or Sclerocactus papyracanthus)

The above-mentioned spines are within the normal length found in most cacti. Interestingly, species of the subfamily Opuntioideae have rather short spines, called glochids.

Tufts of fine and barbed glochids detach easily from the plant. Once they penetrate the skin, it’s nearly impossible to remove them without leaving minute splinters behind. Glochids are a major skin irritant, so keep your distance from prickly pear cacti and cholla.

Areoles

Not all cacti have spines, but they all have areoles. The presence of areoles is the easiest way to tell if a succulent is a cactus. These specialized plant structures are unique to every species.

In one way, areoles are equivalent to buds. They may be sunken spots or raised bumps on the stem from which spines, flowers, and other stems emerge.

The areoles are the cacti’s primary defense mechanism. A typical areole has a single or few sharp spines, surrounded by a cluster of much finer ones. The tangles of spines growing out of the areoles make them appear wooly or hairy.

4.   Fruits

Dragon fruit cactus

Not all succulents bear edible fruit. When they do, they’re typically cactus plants. Here are some cacti that produce exotic but enticing fruits:

  • Dragon fruit cactus (Selenicereus undatus)
  • Prickly pear cactus (Opuntia)
  • Saguaro barrel cactus (Ferocactus cylindraceus)
  • Peruvian apple cactus (Cereus repandus)
  • Cholla cactus (Cylindropuntia)

Wrapping Up

Cacti have distinct physical characteristics that set them apart from succulents. Most cacti have spines instead of leaves, but all have areoles. In addition, fruit-bearing succulents are mostly cacti.

With these in mind, you’ll finally be able to tell the difference between a succulent and a cactus.