Euphorbia is a very large genus of plants with more than 2,000 species. About 1,200 of them are succulents, some with bizarre shapes and wide, fleshy leaves, while others that look remarkably like cacti, complete with spines.
Euphorbia is a somewhat confused genus, with species and subgenera frequently added and deleted. There are annual, perennial, and biennial species within the genus, herbaceous plants and woody shrub species, and both deciduous and evergreen species. The linking characteristic is the presence of a milky white sap that in some species can be toxic. People with sensitivities to latex are most likely to react to the sap of Euphorbia plants.
The species of Euphorbia grown for landscape use or as houseplants are mostly succulent species grown for their architectural shapes and fascinating foliage, but a few are known for their flowers. Most Euphorbias bloom in spring or summer and go dormant in winter. The succulent Euphorbia species common in landscape use or as houseplants often go by the common name of "spurge." You will also see some with more descriptive common names, such as the "basketball euphorbia" (Euphorbia obesa).
|Botanical Name||Euphorbia spp.|
|Common Names||Euphorbia, spurge|
|Plant Type||Most cultivated types are herbaceous perennials|
|Mature Size||Varies by species|
|Sun Exposure||Most species refer full sun|
|Soil Type||Most prefer dry, well-drained soil; indoor plants prefer a cactus potting mix|
|Soil pH||Varies by species; most prefer a slightly acidic to neutral soil (6.0 to 7.0)|
|Bloom Time||Varies by species|
|Flower Color||Varies by species; many have yellow or red blooms|
|Hardiness Zones||5 to 11 (USDA); depends on species|
|Native Area||Africa, Asia, North and South America|
How to Grow Euphorbia Plants
Euphorbias are very easy to care for. They require a little pampering to become established, but once they are, these plants are quite self-sufficient. In fact, more die from too much care and watering than from neglect.
Most of the succulent euphorbias are not frost-tolerant. There are a few evergreen species, like creeping wood spurge, cushion spurge, and donkey-tail spurge that will survive down to USDA Zone 4 or 5, but most Euphorbia species are suitable for zones 6 through 9. A few are tropical species that are hardy only in zones 10 and 11.
Most Euphorbia species do very well when planted a dry, well-drained soil in a sunny location. They often do well in poor, rocky, or sandy soils where other plants languish. Despite the visual similarity to cactus plants, Euphorbias need regular modest watering. Avoid overhead watering, which can cause powdery mildew and other fungal problems. Pruning is required only if the plant's growth gets out of hand.
Euphorbia is an excellent plant for beginners, as it is very hard to kill.
Euphorbia plants prefer a spot in full sun, although some species can tolerate part shade. In hot southern climates, some afternoon shade may be helpful for most species.
All Euphorbias, especially the succulent varieties, need well-draining soil. They will rot if left in the wet soil for a prolonged period. Ideally, they should be planted in a slightly acidic to neutral soil, but most will do fine even in a slightly alkaline soil.
Unlike most succulents, Euphorbia does not handle long periods of drought well. Your plants will weekly watering during the summer during periods without rain, or whenever the soil is dry several inches below the surface. Water deeply, but don't let the plants sit in wet soil, as this can cause root rot.
Temperature and Humidity
Most Euphorbia plants prefer a warm environment with average daytime temperatures around 80 degrees Fahrenheit. They will require more frequent watering when temps turn warmer than this. This is a large genus, however, and temperature and humidity requirements vary by species.
To help your Euphorbias get established and growing well, add some organic matter, like compost, or a balanced, organic fertilizer to the initial planting hole. If you are growing Euphorbia in a container or if your soil is poor, feed with a half-strength fertilizer monthly. A plant that develops yellowing leaves at the bottom is one in need of feeding.
Growing in Containers
When grown in containers, Euphorbia should be planted in a cactus/succulent potting mix, in a container with good drainage. The plant will require a more frequent watering when grown in a container—sometimes two or three times a week in hot weather.
Propagating Euphorbia Plants
Euphorbias can be grown from seed, but the seeds can be difficult to germinate (or even find). This plant is usually propagated by stem cuttings planted in a seed-starter or cactus potting mix. Fresh cuttings can ooze sap which can be a skin irritant, so you may wish to wear gloves when handling them.
Allowing the cut stem to dry overnight will improve your success rate of rooting the cutting, as will the use of some type of rooting hormone.
Toxicity of Euphorbia Plants
The milky sap (latex) of Euphorbia plants is highly toxic and can irritate skin and eyes. This trait evolved as the plant's adaptation for preventing animals and insects from feeding on it. Contact with skin can cause severe skin irritation, and contact with the eyes has been known to cause blurred vision or even blindness. Contact a poison-control agency if the sap is ingested; induced vomiting is often the treatment. For skin and eye contact, flushing with plenty of water is the normal course of action.
Common Pests/ Diseases
Euphorbia plants tend to grow mostly problem-free. Between the milky sap and the spiky needles, few animals find Euphorbias tempting. However, there are a few pests and diseases to be on the alert for:
- Mealybugs and spider mites are the most common pests. They will feed on the plants, weaken, and eventually kill them. The population of both these insects can increase to large numbers rapidly. Catching them early is your best chance of controlling them. Insecticidal soaps and oils are good non-toxic remedies.
- Root rot occasionally occurs, but it's only a problem when plants are allowed to sit in wet soil. Provide well-draining soil and limit watering to when the soil feels dry a couple of inches below the soil surface.
- Although Euphorbias like humidity, they also need good air circulation or they will be susceptible to mildews. Try correcting growing conditions before you resort to spraying fungicide on the plants, which can harm Euphorbia leaves.
Varieties of Euphorbia
Some of the most popular Euphorbia species include:
- Cushion spurge (Euphorbia polychroma) is a clumping perennial growing 12 to 18 inches high with yellow flowers that appear in spring. It is grown in zones 4 to 8.
- Crown of thorns (E. milii) is a bushy evergreen form that can grow up to 6 feet tall when grown outdoors in zones 9 to 11. It can also be grown as a houseplant. Different cultivars offer red, pink, or yellow flowers that bloom repeatedly.
- Basketball euphoria (E. obesa) is a small succulent with a round, ball-shaped stem that gradually becomes cylindrical as the plant ages. It is usually grown as a houseplant, but is hardy outdoors in zones 10 and 11.
- Donkey-tail spurge (E. myrsinites) is a creeping perennial that grows to 1 foot tall with blue-gray foliage with insignificant yellow flowers. It is often used as ground cover in zones 5 to 9.
- Wood spurge (E. amygdaloides) is a bushy evergreen form that grows 18 to 24 inches tall with yellow flowers that appear in mid- to late spring. It is suitable for growing in zones 6 to 8.
- Snow-on-the-mountain (E. marginata) is an annual species grown in zones 2 to 11. It can grow to as much as 3 feet and produces white flowers from mid-summer into fall.
- Mottled spurge (E. lactea) is a large shrub with fan-like scalloped branches and black spines. It grows to as much as 16 feet tall and is hardy in zones 10 and 11.
- Dragon fish bone (E. grandialata) is a thorny, columnar-shaped plant that begins with an upright growth habit but gradually spreads into a bush shape. It has coral red bracts in summer and grows to about 6 feet high with an 8-foot spread. It is grown in zones 9 to 11.