The question of whether native cactus plants exist in Africa is a common source of confusion, largely because the continent hosts an immense diversity of succulent flora. A cactus is scientifically defined as a plant belonging exclusively to the Cactaceae family, a group characterized by specific anatomical structures adapted for water storage. Although Africa contains numerous spiny, fleshy plants thriving in arid environments, most of them belong to entirely different botanical families. Addressing this question requires separating the true cactus lineage from the many species that simply share a similar appearance.
Where Do Cacti Actually Come From?
The Cactaceae family is overwhelmingly endemic to the Americas, establishing its definitive origin in the New World. This vast native range extends from southern Canada, through Central America, and down into the southernmost regions of Chile and Argentina. Cacti evolved separately from the succulent plants of the Old World, including those in Africa and Eurasia.
There is one well-known exception within the entire family: the genus Rhipsalis. Specifically, the species Rhipsalis baccifera, often called mistletoe cactus, has a scattered natural distribution that includes Central and South America, tropical East Africa, Madagascar, and Sri Lanka. Experts believe this outlier colonization occurred naturally, likely through long-distance seed dispersal by migratory birds. While this single species confirms a native cactus presence, it represents a tiny fraction of the Cactaceae family and is not the source of the common confusion seen in African deserts.
The African Cacti You See Everywhere
The large, spiny cacti commonly encountered across the African landscape are not native species but descendants of introduced plants, primarily belonging to the Opuntia genus, known as prickly pears. These species were brought to the continent centuries ago, often by European settlers, for a variety of purposes. They were valued for their edible fruits, use as livestock fodder during drought, and ability to form impenetrable living fences.
The species Opuntia ficus-indica was introduced to the Cape region of South Africa over 300 years ago, where it eventually reverted to its spiny, uncultivated form and became aggressive. Today, prickly pear varieties are widely naturalized or invasive across South Africa, the arid rangelands of East Africa (Kenya and Ethiopia), and throughout North Africa. Opuntia’s ability to thrive in diverse arid zones has allowed it to escape cultivation and form dense thickets that fundamentally alter local ecosystems.
Convergent Evolution and Cactus Look-Alikes
The widespread visual confusion regarding African cacti stems from convergent evolution. This occurs when unrelated species independently evolve similar physical traits in response to environmental pressures, such as the need to conserve water in hot, arid climates. The primary group of native African plants commonly mistaken for cacti are the succulent species in the genus Euphorbia, which is part of the Euphorbiaceae family.
Both cacti and African Euphorbia species have evolved ribbed, fleshy, columnar stems and have shed their leaves to minimize water loss through transpiration. Despite these similarities, a clear anatomical difference separates the two plant families. All true cacti possess areoles, which are specialized, cushion-like structures on the stem from which spines, flowers, and new branches emerge.
In contrast, Euphorbia plants lack these areoles, with their often paired thorns or spines growing directly from the stem tissue. A distinguishing feature is the sap: when a Euphorbia stem is cut, it exudes a milky, latex-like sap that is often toxic and irritating, while cacti do not produce such a substance.
Ecological Impact of Invasive Cacti
The success of introduced Opuntia species in Africa has created significant ecological and economic challenges, particularly in rangelands used for livestock grazing. These invasive plants, such as Opuntia stricta in East Africa, rapidly establish dense stands that outcompete native grasses and shrubs. This displacement of indigenous flora leads to a reduction in biodiversity and decreases the land’s capacity to support native herbivores.
The dense, spiny thickets created by the invasive cacti also physically impede the movement of livestock and wildlife, effectively shrinking the amount of available grazing land. Furthermore, the sharp spines and tiny, barbed hairs, known as glochids, can cause infections, blindness, and death in grazing animals that attempt to consume the pads or fruits.
To manage these large-scale invasions, African nations, including South Africa and Kenya, have implemented biological control programs. These programs primarily use species-specific agents like the cochineal insects (Dactylopius opuntiae), which feed solely on the cactus tissue.