Euphorbia is one of the largest genera of flowering plants, with about 2,420 recognized species. This genus belongs to the very large and diverse family Euphorbiaceae, commonly known as the Spurge Family. The species inhabit a wide range of habitats, from tropical areas in Africa, Madagascar, and the Americas to warmer, temperate regions in Asia and Europe. Some species can also be found in the Pacific Islands and Australia. Most succulent Euphorbias are native to tropical areas of Africa.
The genus was first described by Carl Linnaeus in 1753 based on its type species, Euphorbia antiquorum.
Euphorbias range from annual, biennial, or perennial herbs to woody shrubs or trees, all of which have a poisonous milky sap called latex. About 1,000 species are more or less succulent. The main stems and branches of the succulent Euphorbias are thick and fleshy, thorny, or unarmed. The leaves can be arranged in various patterns, including opposite, alternate, or whorled. In succulent species, the leaves are usually small and short-lived. All members of the genus have unisexual flowers that occur in clusters known as cyathia. Most species are monoecious, producing both male and female flowers on the same plant, while a few are dioecious, producing male and female flowers on separate plants. Fruits are usually three-lobed capsules, almost always ripening to a woody container that splits open, sometimes explosively ejecting its four-angled, oval, or spherical seeds.
Succulent Euphorbias are among the plants most commonly confused with cacti. The species native to desert habitats have thorns, but they differ from the cacti spines.
Plants of the genus Euphorbia are commonly called Spurge, a name that derives from the Middle English or Old French "espurge," meaning "to purge," due to the use of the Euphorbia's sap as a purgative.
The generic name "Euphorbia" probably honors Euphorbus, the Greek physician of King Juba II of Numidia and Mauretania, who married Cleopatra Selene II, the daughter of Antony and Cleopatra.
Growing Conditions for Euphorbia
Euphorbia, native to desert habitats, requires conditions similar to those suitable for cacti. They are ideal for outdoor cultivation in dry, temperate regions, but also thrive as container plants both indoors and outdoors.
Light
Most Euphorbias are sun lovers, but some will tolerate partial shade. Place your indoor Euphorbias in a sunny window. You may place the pots on the balcony or in the garden from spring to fall. Increase sun exposure gradually to prevent sunburn.
Soil
Euphorbias require well-draining soil. They even thrive in poor, dry soils. Use a commercial mixture formulated for succulents, or make your own potting mix.
Temperature
High summer temperatures are not a problem for succulent Euphorbias, but minimum winter temperatures vary. The species from Arabia, West Africa, Central Africa, and the tropical and subtropical regions of the Americas require temperatures between 55°F and 60°F (13°C and 15°C) in winter. The species from Madagascar and East Africa require temperatures between 50°F and 55°F (10°C and 13°C), while species from South and North Africa require temperatures below 50°F (10°C). Some species from South Africa will survive a few degrees of light frost for a short period if kept dry.
Pot Size
Select a pot 2 to 3 inches (5 to 7.5 cm) larger in diameter than the plant's base. Use only pots with at least one drainage hole in the bottom.
General Care for Euphorbia
Euphorbias are easy to care for if the growing conditions are right.
Watering
Succulent Euphorbias can survive drought, but that does not mean they need it. Water from spring to fall when the top inch (2.5 cm) of soil feels dry. Reduce watering in winter. Give them just enough water to prevent wilting. The best time of day to water your Euphorbias during the warm season is in the evening. Watering in the morning, before temperatures rise, is also acceptable, and it may even be beneficial during the winter months.
Fertilizing
Each species has its own unique nutritional requirements, but all Euphorbia species will benefit from fertilizer. Plants in pots need regular feeding. Apply a balanced fertilizer in a 10-10-10 NPK formulation, diluted to 1/4 strength weekly during the growing season.
Pruning
Some Euphorbias require regular pruning to control their size and prevent them from becoming overgrown. When pruning Euphorbias, always wear gloves, use eye protection, and avoid contact with the milky sap, as it is a strong irritant to the skin.
Repotting
Euphorbias will benefit from repotting, but they do not require repotting annually. When your Euphorbia outgrows its pot, it is time to repot the plant in a larger pot and provide it with fresh potting mix. The repotting is best done in early spring, at the beginning of the growing season. Wait for a week or two before watering the repotted plant. Wear gloves, protective clothing, and appropriate eye protection when repotting all Euphorbias.
How to Propagate Euphorbia
The most common and efficient method of propagation for many species is using cuttings. Euphorbias can also be grown from seeds, but they can be challenging to germinate and sometimes difficult to find.
Cuttings
Use a sharp, clean knife to take cuttings. If possible, cut the branching species at the point where it branches. Solitary plants can be decapitated to encourage the production of offsets that can later be removed and rooted. The best time to take cuttings is in spring or summer. Wash away the milky sap that appears after cutting in a glass of water or by spraying. Allow the cutting to callus for several days before placing it in a well-draining soil mix. Dusting the cut surface with a rooting hormone powder will help roots form. Rooting can take longer than expected, but is sped up by raising the soil temperature to around 77°F (25°C).
The two-step cutting method is required for Medusoid Euphorbias and some other species. First, take a cutting in the usual way. When it has rooted, make a second cut just above the point where the roots have formed.
Some Euphorbia species from Madagascar are successfully propagated from leaf cuttings.
Seeds
Sow Euphorbia seeds in a commercial seed-growing mix or well-drained soil in spring. Keep the soil moist until the seeds germinate. At temperatures between 70°F and 80°F (21°C and 27°C), germination typically occurs within 1 to 2 weeks.
Grafting
Several rare and delicate Euphorbia species are grafted because they are easier to keep, grow faster, and produce more flowers on more vigorous stocks.
Pests and Diseases of Euphorbia
Euphorbias are less susceptible to pests and diseases than many other succulents.
Pests
The most common pests on Euphorbias are mealybugs, spider mites, scale, and whiteflies. These pests are difficult to control because they are small and excellent at hiding, making them hard to spot. Correct pest identification is the first and most crucial step in selecting the most efficient control options.
Diseases
Mildew is a fungal disease that appears as a white or gray powdery film on parts of the plant. It is caused by high humidity, poor ventilation, insufficient light, and a lack of nutrients. Isolate Euphorbias that start showing powdery mildew symptoms. Neem oil is a good choice for reducing or eliminating mild to moderate mold infections.
Toxicity of Euphorbia
All Euphorbia species produce a white milky sap that is toxic and can cause irritation to the skin and eyes. It is best to keep plants out of the reach of children and pets.
Links
- Back to genus Euphorbia
- Succupedia: Browse succulents by Scientific Name, Common Name, Genus, Family, USDA Hardiness Zone, Origin, or cacti by Genus