The Euphorbia genus contains thousands of species of plants, more than 450 of which are succulents. Though many Euphorbia succulents have cactus-like thick green skin and sharp spines, no Euphorbias are true cacti. Most of these striking plants came originally from Arica and Madagascar, as well as from India and the Canary Islands. Euphorbia succulents can be cared for in a similar manner to cacti.
Euphorbias will thrive only in well-drained soil. Use a commercial cactus or succulent soil mix, and add gravel or pumice to increase drainage. To fortify your Euphorbia, give your plant a low-nitrogen, water-soluble fertilizer that's been diluted to 1/4 strength. Fertilizing two or three times a month during the growing season is ideal.
Euphorbias differ slightly from cacti in that they will not do well in desert light. Bright, indirect light is optimal for these plants, which may sunburn in strong summer sun. A covered outdoor patio, alcove or a particularly bright spot indoors is ideal for Euphorbias. Hardy Euphorbias may be placed outdoors in a dry place with lots of light in the winter.
Most Euphobias are hardy in USDA zones 5 to 9, although many species can handle colder weather. The gardening zone required for a Euphorbia varies, so check that your species can handle cold weather.
Like most cacti and succulents, Euphorbias require minimal amounts of water. Water just once a week during the hotter spring and summer months, and once a month during cool fall and winter months. Spread the water evenly throughout the pot. Euphorbias are prone to fungal infections, and overwatering can lead to an infection and death. It is always better to not water enough than to water too much.
Some of the most common types of nursery Euphorbias include the Euphorbia meloformis, a 1- to 3-inch, squat, round, cactus-like plant that is native to South Africa, and the Euphorbia lactea, or Elk Horn, a spiny plant native to India that can grow up to 6 feet, even in low light levels. The Euphorbia flanaganii, or Medusa's Head, is an exotic Euphorbia from South Africa with multiple snake-like branches. The Medusa's Head will flower indoors.
As a defense against herbivores, Euphorbias will bleed a thick, milky white sap if cut open or damaged. The sap can cause mild to moderate skin inflammation, and serious complications if you get it in your eyes. The vapors from a large plant's sap can also cause eye burning. Immediately wash sap off skin, and consider using gloves when handling the plant. Once the sap has dried, it is not water soluble; wash off dried sap with milk or hand cream. The sap is also highly toxic if swallowed. Take extra caution if growing a Euphorbia plant in a household with pets or children.