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 and others that look remarkably like cacti, complete with spines. Growers commonly refer to plants in the genus as euphorbia or spurge. Euphorbia is a somewhat confusing genus, with species and subgenera frequently added and deleted. There are annual, perennial, and biennial species within the genus. You'll find herbaceous plants and woody shrub species, as well as both deciduous and evergreen species. The linking characteristic among the species is the presence of a milky white sap in the plants.
The species of Euphorbia grown for landscape use or as houseplants are mostly succulents, which feature fascinating shapes and foliage, but a few are known for their flowers. Most Euphorbias bloom in the spring or summer and go dormant in the winter. In general, it’s best to plant most species in the spring after the threat of frost has passed, though houseplants typically can be started at any point. The species' growth rates vary, from slow to fairly quick.
|Botanical Name||Euphorbia spp.|
|Common Names||Euphorbia, spurge|
|Plant Type||Herbaceous, succulent|
|Mature Size||6–36 in. tall and wide (on average)|
|Soil Type||Sandy, well-drained|
|Soil pH||Acidic, neutral|
|Bloom Time||Varies by species|
|Flower Color||Varies by species; many have yellow or red blooms|
|Hardiness Zones||5–11 (USDA)|
|Native Area||Africa, Asia, North America, South America|
|Toxicity||Toxic to people and pets|
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, especially overwatering, than from neglect. However, they are fairly hardy and make great plants for beginners.
It's critical to provide your Euphorbia with soil that has sharp drainage. Soggy soil can quickly cause root rot and kill a plant. If you're growing your plant in a container, it should have ample drainage holes. An unglazed pot is best because it will allow excess moisture to escape through its walls as well as through the drainage holes. Provide your plant with lots of light and periodic watering. Avoid overhead watering, which can cause powdery mildew and other fungal problems on the foliage. Pruning is typically only necessary for overgrown plants to bring them back to a manageable size.
Euphorbia plants prefer a spot in full sun, meaning at least six hours of direct sunlight on most days, though some species can tolerate part shade. In hot climates, some afternoon shade can be helpful for most species.
All Euphorbias, especially the succulent varieties, need well-draining soil. A sandy soil with a slightly acidic to neutral soil pH 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.
Water whenever the top couple inches of soil feels dry from spring to fall when the plant is actively growing. During the winter, reduce watering to only when the plant shows signs of wilt.
Temperature and Humidity
Most Euphorbia species can tolerate hot temperatures and prefer a warm environment with average daytime temperatures around 80 degrees Fahrenheit. Cold tolerance varies among the species. Some will handle a light frost while others don’t grow well in temperatures below roughly 55 degrees Fahrenheit. Humidity tolerance also varies. It’s important to have good ventilation around the plants if there is high humidity to prevent fungal disease.
Feeding requirements vary by Euphorbia species, but in general all of the plants will benefit from some fertilizer. Adding compost or a balanced organic fertilizer to a new plant will help to promote healthy growth. Then, many Euphorbia species will do fine with a weak liquid fertilizer applied throughout the growing season. Container plants typically need more feeding than ones grown in the ground. And a plant that develops yellowing leaves at the bottom is one that's in need of feeding.
Euphorbias can be grown from seed, but the seeds are difficult to germinate (or even find). This plant is usually propagated by stem cuttings planted in a seed-starting mix or cactus potting mix. Fresh cuttings can ooze sap and irritate the skin, so 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 a rooting hormone. Keep the growing medium lightly moist as the cutting develops roots. Once you feel resistance when you gently tug on the stem, it is ready to be planted wherever you plan to grow it.
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, 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 an afflicted plant's growing conditions first before resorting to fungicides.
These are some of the most popular Euphorbia species:
- 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 (Euphorbia milii) is a bushy evergreen plant that can grow up to 6 feet tall outdoors in zones 9 to 11. It can also be grown as a houseplant but typically won't reach its maximum size indoors. Different cultivars offer red, pink, or yellow flowers that bloom repeatedly.
- Basketball euphoria (Euphorbia 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 (Euphorbia myrsinites) is a creeping perennial that grows to 1 foot tall with blue-gray foliage and insignificant yellow flowers. It is often used as ground cover in zones 5 to 9.
- Wood spurge (Euphorbia amygdaloides) is a bushy evergreen 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.