The Euphorbia genus of plants is most well-known for its succulent species which are elegant and architectural in appearance.
These plants are often mistaken for cacti due to many of the popular varieties being stem succulents. However, they are really an entirely unique genus unto themselves that includes over 2000 species!
This post will cover what makes Euphorbia so special and unique, why it is not cacti, how to care for Euphorbia, what some popular species are, and more.
Keep reading to enter the expansive and fascinating world of Euphorbia!
Table of Contents
- What is a Euphorbia plant?
- Why isn’t a Euphorbia classified as a cactus?
- What do Euphorbia and Cacti have in common?
- What are some unique characteristics of and facts about Euphorbia?
- Where are Euphorbias found in the wild?
- How are Euphorbias generally cared for?
- Are Euphorbia plants pet-safe?
- What are some popular species of Euphorbia?
- Related Posts
What is a Euphorbia plant?
Euphorbia is not a single plant, but a genus of plants consisting of over 2000 species!
They are part of the family Euphorbiaceae, also called the Spurge family.
It is estimated that a little less than half of the species in the Euphorbia genus are succulent. Many of the species that are popular as houseplants are succulents because they do well with minimal watering and adequate lighting– in addition to being strikingly beautiful.
Euphorbia species range from specimens that look a lot like cacti to the poinsettias that many people buy around the holidays.
Yes, poinsettias really are a Euphorbia – Latin name Euphorbia pulcherrima!! Poinsettias are a great example of a non-succulent variety of Euphorbia.
All plants in this family have a milky white sap that oozes out when cut.
Many Euphorbia plants are xerophytic, which means they are designed to thrive and survive in harsh environments with little water.
Why isn’t a Euphorbia classified as a cactus?
While many species of Euphorbia do look strikingly similar to cacti, they are missing some key features that botanists use to identify cacti:
- Cacti have areoles, which are cushion-like bumps that form on a cactus’ flesh. The areole is where spines, new growth, flowers, and more grow from and is a feature that only cacti have.
- Some species of euphorbia are also mistaken for cacti because they have growths that look a bit like a cacti’s spines. The spines on cacti are modified leaves whereas the growths on euphorbias are thorns.
- Most, if not all, euphorbias do grow leaves. The more succulent species have leaves that are smaller, more compact, and short-lived than the traditional leaf we think of, however.
What do Euphorbia and Cacti have in common?
Many species of euphorbia are stem succulents, like cacti, and as such have become biologically similar in some ways to cacti. This is because they are both coping with the same environmental conditions – hot, dry desert.
These stem succulents have adapted to use their stems to absorb energy for photosynthesis rather than leaves, which allows them to hunker down and store as much water as possible within their stems while still being able to produce energy and food.
Many succulent euphorbias also use CAM photosynthesis. This process is uniquely suited for desert environments to help plants to minimize water loss while the sun is up.
Click to read more about CAM photosynthesis
Plants that do not live in a harsh environment open their stomata (pores for gas exchange) during the day to absorb carbon dioxide.
Carbon dioxide is one of the essential components of photosynthesis. Photosynthesis requires carbon dioxide, water, and light.
When a plant’s stomata are open, water evaporates through these passages. If a plant is living in an average rainfall or even tropical environment, this may not be a big deal so opening their stomata during the daytime presents a much lower risk.
However, for plants located in places where rainfall is extremely minimal, they want to preserve as much of this water as possible.
As such, plants that utilize CAM photosynthesis will close their stomata during the day and use stored carbon dioxide and water for photosynthesis.
Then at night, they will open their stomata to absorb carbon dioxide when temperatures are much lower and therefore the rate of evaporation is much lower as well.
What are some unique characteristics of and facts about Euphorbia?
- All Euphorbia plants have white, latex sap. This sap is varying levels of toxic.
Because of its toxicity, when pruning or taking cuttings of these plants, people are advised to wear gloves and to be very careful not to get the sap in their eyes or on their skin. People have had very serious adverse reactions so extreme caution should be taken.
- Euphorbia is also referred to as the Spurge family. The word “spurge” originates from the French word “espurgier” which means “to purge.” Why would its name mean to purge? Some of these plants have been used as purgatives in medicine!
- The flowers on a Euphorbia plant are unisexual – meaning that each flower has only a male part (stamen) or a female part (pistol).
These flowers grow in clusters or inflorescences called cyathium. This flower structure is unique to euphorbia plants.
Where are Euphorbias found in the wild?
Most euphorbia species are found in Africa and Madagascar. They are particularly well adapted to survive in regions that are warm, receive little water, and have large amounts of sunlight year-round.
How are Euphorbias generally cared for?
Soil: Euphorbia like a very well-draining soil where their roots will not sit for long in moisture as they are prone to root rot.
Light: They like full sun to bright indirect light, depending on the species.
Water: These plants can tolerate periods of drought, but do not necessarily like long periods of drought. They prefer to be watered when completely dry. This is different from cacti, which can go long periods of time with completely dry soil and often do well in these conditions.
Note – Some sites recommend providing water under the leaves (when applicable) to avoid powdery mildew.
Pot: A pot with good drainage should be chosen to ensure the plant doesn’t sit in soggy, wet soil for long to avoid root rot.
Fertilizer: An organic cactus fertilizer can be used once or twice per month during the growing season when a euphorbia stem succulent hasn’t been newly repotted. If it is a leafier variety, a balanced organic fertilizer could be utilized instead. Cacti fertilizers are usually low in nitrogen because they do not need to support the growth of foliage.
If using chemical fertilizer, it is recommended to use a quarter or half the recommended strength to ensure the plant does not experience burnout or unhealthy, rapid growth.
Are Euphorbia plants pet-safe?
Euphorbia plants are not pet-safe. Just as species are varying levels of toxic for humans, Euphorbia species have varying levels of toxicity for pets as well. Even the very common poinsettia is mildly toxic to dogs and cats. If you have any questions or concerns about a particular species of Euphorbia, make sure to check the ASPCA website linked here and search for your specific plant.
What are some popular species of Euphorbia?
Euphorbia milii
Euphorbia milii is commonly referred to as the Crown of Thorns. These unique plants are succulent in nature and, as such, can go long periods of time without water. They thrive in sunny locations suited for other desert succulents. Euphorbia milii is available in a range of colors and cultivars, typically flowering in spring and summer.
Euphorbia obesa
Euphorbia obesa is also known as the Baseball plant due to its ball-like appearance and size. It can tolerate periods of drought and thrives in sunny locations. E. obesa is a very unique and low maintenance plant that also blooms small flowers in summer near the top of the plant.
Euphorbia lactea ‘White Ghost’
Euphorbia lactea ‘White Ghost’ is also commonly referred to as Dragon Bones, Grey Ghost, or the Candleabra Cactus. This plant thrives in bright indirect light and prefers to be watered when its soil is completely dry. This one is my personal favorite among the popular Euphorbias!
Euphorbia trigona and Euphorbia trigona ‘Rubra’
These plants, both the green variety (Euphorbia trigona) and the red variety (Euphorbia trigona ‘Rubra’) are commonly called African Milk Tree. The green plant is used as a hedge in some areas of Africa, but its most common use is as a houseplant. Euphorbia trigona ‘Rubra’ is a cultivated variety, popular for its beautiful red color. These plants love lots of sun, water when dry, and the same general care as other succulents.
***E. trigona is one species that is known for causing mild to severe skin irritation and serious complications if its sap touches someone’s eyes.
Euphorbia horrida (Pictured is the cultivar ‘Nova’)
Euphorbia horrida is also referred to as the African Milk Barrel. This plant earned its name– horrida (meaning rough and bristly)– due to its long and plentiful spikes. These spikes are not present in the pictures below of my very juvenile E. horrida. Like most other succulent Euphorbias, this plant likes bright light, watering when dry, and well-draining soil as it is prone to root rot.
Euphorbia ammak variegated
Euphorbia ammak is the largest plant of those listed here. Commonly called the African Candlabra, it can grow between 30 and 40 feet tall! The variety that is typically available for purchase as a houseplant is represented below, showing its creamy yellow and green variegation. It’s care is identical to other succulent Euphorbias.
Euphorbia marginata
Euphorbia marginata is the only species on the list that isn’t a succulent! Commonly called Snow-on-the-Mountain due to its white variegation, this plant can be found in parts of the United States and Canada. It is an annual prairie plant that is used by some in outdoor gardens or landscaping.
Resources used for this article:
https://euphorbiaceae.org/pages/about_euphorbia.html
https://www.euphorbia-international.org/euphorbias/cultivation/about_euph_cultivation_watering.htm
https://deepblue.lib.umich.edu/bitstream/handle/2027.42/109954/evo12534.pdf?sequence=1&isAllowed=y
http://www.indefenseofplants.com/blog/2015/9/18/cam-photosynthesis
I thought you might mention the fact that Harry Dunaway invented euphorbia Keisi. I don’t know if Mr. Dunaway is still living however years ago he distinguished himself by holding a masters degree from Columbia University in the field of endeavor you have written about. As the co-owner of Dunaway’s nursery, he actively supervised the operation in addition to creating the species Keisi (I believe this is a misspelling, please correct). Please remark.
Hi Dennis, thank you so much for the interesting information and the correction! I’ll certainly amend the article to include the info you shared!