Euphorbia plants (Euphorbia spp.) also go by the easier to say, but less elegant, name of Spurge. They are a family of plants that may be grown as houseplants or occasionally outdoors. There are many varieties of Euphorbia plants, with fascinating forms that range from shrubs, herbs, or cactus-like specimens. Growing Euphorbias is easy and some are hardy in temperate climates. These are easy to start from seed and propagate from cuttings. Learn how to cultivate a Euphorbia plant that will start conversations and cause second looks.
I. Appearance and Characteristics
Euphorbia is a very large and diverse genus of flowering plants, commonly called spurge, in the family Euphorbiaceae. “Euphorbia” is sometimes used in ordinary English to collectively refer to all members of Euphorbiaceae (in deference to the type genus), not just to members of the genus.
Euphorbias range from tiny annual plants to large and long-lived trees. with perhaps the tallest being Euphorbia ampliphylla at 30 m (98 ft) or more. The genus has roughly 2,000 members, making it one of the largest genera of flowering plants. It also has one of the largest ranges of chromosome counts, along with Rumex and Senecio. Euphorbia antiquorum is the type species for the genus Euphorbia. It was first described by Carl Linnaeus in 1753 in Species Plantarum.
The plants are annual, biennial or perennial herbs, woody shrubs, or trees with a caustic, poisonous milky latex. The roots are fine or thick and fleshy or tuberous. Many species are more or less succulent, thorny, or unarmed. The main stem and mostly also the side arms of the succulent species are thick and fleshy, and often winged, 15–91 cm (6–36 in) tall. The succulent trees and large shrubs are mostly confined to southern and eastern Africa, but Euphorbia neutra is native to the Caatinga of Brazil and Euphorbia royleana is found in the Himalayan foothills. The deciduous leaves may be opposite, alternate, or in whorls. In succulent species, the leaves are mostly small and short-lived. The stipules are mostly small, partly transformed into spines or glands, or missing.
Like all members of the family Euphorbiaceae, spurges have unisexual flowers.
In Euphorbia, flowers occur in the head, called the cyathium (plural cyathia). Each male or female flower in the cyathium head has only its essential sexual part, in males the stamen, and in females the pistil. The flowers do not have sepals, petals, or nectar to attract pollinators, although other nonflower parts of the plant have an appearance and nectar glands with similar roles. Euphorbias are the only plants known to have this kind of flower head.
Nectar glands and nectar that attract pollinators are held in the involucre, a cup-like part below and supporting the cyathium head. The “involucre” in the genus Euphorbia is not to be confused with the “involucre” in family Asteraceae members, which is a collection of bracts called phyllaries, which surround and encase the unopened flower head, then support the receptacle under it after the flower head opens.
The involucre is above and supported by bract-like modified leaf structures (usually in pairs) called cyathophylls’, or cyathial leaves. The cyathophyll often has a superficial appearance of being petals of a flower.
Euphorbia flowers are tiny, and the variation attracting different pollinators, with different forms and colors occurs, in the cyathium, involucre, cyathophyll, or additional parts such as glands that are attached to these.
The collection of many flowers may be shaped and arranged to appear collectively as a single individual flower, sometimes called a pseudanthium in the Asteraceae, and also in Euphorbia.
The majority of species are monoecious (bearing male and female flowers on the same plant), although some are dioecious with male and female flowers occurring on different plants. It is not unusual for the central cyathia of a cyme to be purely male, and for lateral cyathia to carry both sexes. Sometimes, young plants or those growing under unfavorable conditions are male only, and only produce female flowers in the cyathia with maturity or as growing conditions improve.
The female flowers reduced to a single pistil usually split into three parts, often with two stigmas at each tip. Male flowers often have anthers in twos. Nectar glands usually occur in fives, may be as few as one, and may be fused into a “U” shape. The cyathophylls often occur in twos, are leaf-like, and may be showy and brightly coloured and attractive to pollinators, or be reduced to barely visible tiny scales.
The fruits are three- or rarely two-compartment capsules, sometimes fleshy, but almost always ripening to a woody container that then splits open, sometimes explosively. The seeds are four-angled, oval, or spherical, and some species have a caruncle.
II. How to Grow and Care
Sunlight
Euphorbia plants prefer full sun, meaning at least six to eight hours of direct sunlight on most days, though some species can tolerate partial shade. In hot climates, some afternoon shade can be helpful for most species.
Temperature and Humidity
Most euphorbia species can tolerate hot temperatures and prefer a warm environment with average daytime temperatures about 80 degrees Fahrenheit. Cold tolerance varies among the species. Some will handle a light frost while others don’t grow well in temperatures below about 55 degrees Fahrenheit. Humidity tolerance also varies. To prevent fungal diseases, it’s important for the plants to have good ventilation around them in high humidity climates.
Watering
From spring to fall, when the plant is actively growing, water whenever the top few inches of soil feel dry. During the winter, reduce watering to only when the plant shows signs of wilt.
Soil
All euphorbias, especially the succulent varieties, need well-draining soil. A sandy soil with a slightly acidic to neutral soil pH between 5.0 and 7.0 is best, though most will do fine in slightly alkaline soil as well. When grown in containers, euphorbia should be planted in a cactus/succulent potting mix.
Fertilizing
Feeding requirements vary by euphorbia species, but in general, all of them will benefit from some fertilizer. Adding compost or a balanced organic fertilizer to a new plant will help to promote healthy growth. After that initial feeding, many Euphorbia species will do fine with a weak liquid fertilizer applied throughout the growing season. For the amount to use, follow the product label instructions.
Container-grown plants typically need more feeding than plants grown in the ground. And a plant that develops yellowing leaves at the bottom is one that’s in need of feeding.
Pruning
Propagation
Euphorbias can be grown from seed, but the seeds are difficult to germinate (or even find). Therefore, this plant is usually propagated by stem cuttings, ideally in the spring when the new growth starts but propagation can also be done in the summer.
- Using a sharp, clean knife, take a tip cutting at least three inches long. Fresh cuttings can ooze milky sap and irritate the skin, so wear gloves when handling them.
- Allow the cut stem to dry and callous over at least overnight, better for a couple of days. This will improve your success rate.
- Fill a four-inch pot with seed-starting mix or cactus potting mix and water it slowly until evenly moist.
- Dip the cutting in rooting hormone and insert it at least 1/3 of an inch into the soil.
- Keep the growing medium slightly moist as the cutting develops roots.
Once you feel resistance when you gently tug on the stem, it is ready to be planted in a larger container or in a garden bed.
Potting and Repotting
If you grow euphorbia as a houseplant, choose a special potting mixture blended for cacti and succulents that drains quickly. Alternatively you can also mix together three parts potting soil, three parts coarse sand or gravel, and two parts perlite or pumice. A terra cotta pot works best because the porous nature of the material wicks away moisture from the soil and helps prevent root rot.
Pests and Diseases
Euphorbia plants tend to be mostly problem-free. Between the milky sap and the spiky needles, few insects find euphorbias tempting. However, be on alert for a few pests. Mealybugs and spider mites are the most common pests. They will feed on the plants, weakening and eventually killing them. The population of both these insects can increase to large numbers rapidly. So catching them early is your best chance of controlling them. Insecticidal soaps and oils are good nontoxic remedies.
Furthermore, root rot and fungal diseases can occur when conditions are too moist. Try to correct the plant’s growing conditions first before resorting to fungicides.
III. Types of Euphorbias plants to grow
With many Euphorbia varieties to choose from, here is a selection of the most popular and easy to grow Euphorbia plants.
- Euphorbia myrsinites: its creeping habit makes it a useful evergreen ground cover plant with overlapping blue-grey leaves on stems up to 35cm long and clusters of lime green flowers.
- Euphorbia Diamond Frost: is a tender perennial Euphorbia which is often grown as an annual for its tiny white flowers like slivers of ice. Useful for containers and hanging baskets.
- Euphorbia amygdaloides var. robbiae: a low-growing Euphorbia plant (to 50cm) with a spreading habit which copes well with dry shade. Greenish yellow flowers rise from dark evergreen rosettes. Euphorbia amygdaloides var. Purpurea has deep purple leaves and stems, lime green flowers and can reach 1m.
- Euphorbia palustris: the marsh spurge prefers to grow in moist soil in full sun. Growing to between 50cm to 1m, it bears clusters of bright yellow-green flowers in late spring.
- Euphorbia griffithii: distinctive for its orange flowers in early summer, this Euphorbia plant grows to between 50cm and 1m and dies back over the winter. Euphorbia griffithii Fireglow is another red Euphorbia with red-tinged leaves and orange-red flowers.
- Euphorbia x martinii: bearing narrow mid-green leaves and bright lime green bracts with a red eye, this weed-smothering evergreen grows in upright clumps reaching approximately 1m. Euphorbia x martinii Ascot Rainbow has pinkish leaves aging to creamy yellow.
- Euphorbia characias: reaching 1.2m this evergreen Euphorbia has striking spherical or cylindrical flowerheads made up of clusters of purple-lined green flowers with bright yellow centres. Euphorbia characias subsp. Wulfenii is similar but without the purple colouring.
- Euphorbia mellifera: the honey spurge is a handsome shrub from Madeira up to 2m tall with brown honey-scented flowers in late spring.
IV. Uses and Benefits
Several spurges are grown as garden plants, among them poinsettia (E. pulcherrima) and the succulent E. trigona. E. pekinensis (Chinese: 大戟; pinyin: dàjǐ) is used in traditional Chinese medicine, where it is regarded as one of the 50 fundamental herbs. Several Euphorbia species are used as food plants by the larvae of some Lepidoptera (butterflies and moths), like the spurge hawk moths (Hyles euphorbiae and Hyles tithymali), as well as the giant leopard moth.
Ingenol mebutate, a drug used to treat actinic keratosis, is a diterpenoid found in Euphorbia peplus.
Euphorbias are often used as hedging plants in many parts of Africa.