Introduction to Cacti and Euphorbia Succulents
Similar families of plants with distinct differences. While walking in a cactus garden you may see Euphorbia succulents planted and think that they are indeed just a different kind of cactus. Euphorbia succulents( not cacti) are a completely different family of succulent plants than cacti with very interesting similarities and differences.
The Cactaceae family, with over 1,750 species, is native primarily to the Americas and includes iconic plants such as the saguaro cactus and the prickly pear. Cacti are easily recognizable for their spiny stems and adaptation to arid environments.
In contrast, the Euphorbiaceae family, with over 6,000 species, is distributed globally and includes a wide range of forms. This family is particularly diverse in Africa and Madagascar, where many Euphorbia species have evolved succulent traits that mimic cacti in appearance and function.
Similarities Between Cacti and Euphorbia Succulents
1. Adaptations for Water Storage
Both plant families have adapted to store water in their tissues, enabling them to survive prolonged droughts. These adaptations include thick, fleshy stems and reduced or absent leaves to minimize water loss through transpiration.
2. Spines for Protection
Spines, an iconic feature of cacti, serve to protect the plant from herbivores and reduce water loss by casting shade. Euphorbia succulents often have similar defensive structures, though their spines arise differently.
3. CAM Photosynthesis
Both groups use Crassulacean Acid Metabolism (CAM) photosynthesis, an adaptation for conserving water in hot, dry climates. By opening their stomata at night, these plants minimize moisture loss during photosynthesis.
4. Convergent Evolution
The similarities in appearance between cacti and Euphorbia succulents are a classic example of convergent evolution, where unrelated species evolve similar traits in response to similar environmental challenges. Both exhibit columnar shapes, ribbed stems, and spherical forms, which optimize water storage and reduce surface area exposed to sunlight.
5. Shared Ecological Niches
Cacti and Euphorbia succulents often occupy similar ecological niches. While cacti dominate arid landscapes in the Americas, Euphorbia succulents play a similar role in the deserts of Africa and Madagascar.
Key Differences Between Cacti and Euphorbia Succulents
1. Taxonomy and Evolution
Cactaceae belongs to the order Caryophyllales, while Euphorbiaceae is part of the order Malpighiales. These families diverged early in the evolutionary history of flowering plants, and their similarities are entirely due to environmental pressures rather than shared ancestry.
2. Areoles
A defining feature of cacti is the presence of areoles—small, specialized structures from which spines, flowers, and new growth emerge. Euphorbia succulents lack areoles, and their spines arise directly from the stem tissue or modified leaves.
3. Flower Structures
Cactus flowers are often large, showy, and designed for pollination by animals such as birds, bats, and insects. In contrast, Euphorbia flowers are typically small and grouped into unique structures called cyathia, which are surrounded by colorful bracts in some species.
4. Geographic Origins
Cacti are native to the Americas, with only a few species (such as Rhipsalis baccifera) found outside this region. Euphorbia succulents, however, are native to Africa, Madagascar, and parts of Asia.
Highlighting Unique Species: Cacti
1. Saguaro (Carnegiea gigantea)
The saguaro is one of the most iconic cacti, native to the Sonoran Desert in the southwestern United States and Mexico. These towering plants can reach heights of up to 40 feet and live for over 150 years. Their white, night-blooming flowers are pollinated by bats, and their fruits are a vital food source for desert animals.
2. Prickly Pear (Opuntia spp.)
Prickly pear cacti are easily recognizable by their flat, paddle-shaped stems. They produce vibrant flowers and edible fruits, commonly known as "tunas." Native to the Americas, these cacti have been introduced to other regions and are now cultivated for food, livestock feed, and ornamental purposes.
3. Golden Barrel Cactus (Echinocactus grusonii)
Native to Mexico, the golden barrel cactus is prized for its spherical shape and bright yellow spines. It is a popular choice for desert landscaping and succulent gardens.
4. Christmas Cactus (Schlumbergera spp.)
Unlike desert-dwelling cacti, Christmas cacti are native to the rainforests of Brazil. They are epiphytic, growing on trees rather than in the soil, and are known for their colorful, tubular flowers that bloom around the holiday season.
Highlighting Unique Species: Euphorbia Succulents
1. Moroccan mound (Euphorbia resinifera)
Native to the highlands of Morocco, the Morrocan mound is a popular ornamental plant. It features spiny, symmetrical, succulent stems, making it a striking addition to gardens and indoor spaces.
2. Pencil Cactus (Euphorbia tirucalli)
This striking Euphorbia has thin, pencil-like stems and can grow into a large shrub or small tree. Native to Africa, it is often used as a natural fence or for erosion control in arid regions. The "firesticks" variant has stems that turn a red-orange color due to different environmental conditions. Heat, cold, sun exposure and drought stress intensify the colors of the "Firesticks" stems.
3. Royal Spurge (Euphorbia royaleana)
Euphorbia royaleana, a striking succulent native to the Himalayan region, specifically India, Nepal, and Bhutan. Known for its columnar growth habit, this plant stands tall with multiple branches that form a sculptural and dynamic structure.
4. Candelilla (Euphorbia anti-syphilitica)
Native to the Chihuahuan Desert, this plant features striking powdery blueish-gray stems that grow to about 1 foot tall and 4 feet wide—ideal as groundcover or in containers. Its hardy nature and unique appearance make it a standout choice for any garden or landscape.
Ecological and Cultural Roles
Cacti
Cacti play vital roles in desert ecosystems. They provide food, water, and shelter for a variety of animals, from birds and bats to insects and reptiles. Many cacti also have cultural significance, such as the Organ Pipe cactus, that still provide food for Indigenous peoples in the Americas.
Euphorbia Succulents
Euphorbia succulents are equally important in their native habitats. They provide habitat and food for insects and animals and are used by humans for a variety of purposes, including traditional medicine, erosion control, and ornamental landscaping.
Distinguishing Between Cacti and Euphorbia Succulents
To identify whether a plant is a cactus or a Euphorbia succulent, consider the following tips:
- Check for Areoles: Spines emerging from areoles indicate a cactus.
- Inspect the Sap: Milky, latex-like sap suggests a Euphorbia, while clear sap points to a cactus.
- Examine the Flowers: Large, colorful flowers are typical of cacti, while Euphorbias have small, clustered flowers.
- Geographic Context: Plants native to the Americas are likely cacti, while those from Africa or Madagascar are more likely Euphorbias.
Conclusion
The families Cactaceae and Euphorbiaceae are prime examples of how evolution shapes organisms to adapt to similar environmental challenges. While their similarities can make them difficult to distinguish, their differences reflect their unique evolutionary paths and ecological roles. By appreciating the diversity and beauty of these plants, we gain a deeper understanding of the resilience and adaptability of life on Earth. Whether you’re cultivating a succulent garden or exploring the desert, the fascinating world of cacti and Euphorbia succulents offers endless opportunities for discovery and admiration.
