Euphorbia Milii is an ornamental cactus-like plant native to Madagascar and other tropical regions throughout the world. The plant was first introduced into cultivation by Baron Milius, a Governor of Réunion (Bourbon Island), hence the name Milii.
I. Appearance and Characteristics
Euphorbia milii, the crown of thorns, Christ plant, or Christ’s thorn, is a species of flowering plant in the spurge family Euphorbiaceae, native to Madagascar. The species name commemorates Baron Milius, once Governor of Réunion, who introduced the species to France in 1821.
The native Malagasy name for this plant is songosongo also applied to several other Euphorbia species. It is imagined that the species was introduced to the Middle East in ancient times, and legend associates it with the crown of thorns worn by Jesus. It is commonly used as an ornamental houseplant that can be grown in warmer climates. The common English name is due to the thorns and deep red bracts referring to the crown thorn Jesus had to wear during his crucifixion and his blood.
It is a woody succulent subshrub or shrub growing to 1.8 m (5 ft 11 in) tall, with densely spiny stems. The straight, slender spines, up to 3 cm (1.2 in) long, help it scramble over other plants. The fleshy, green leaves are found mainly on new growth, and are up to 3.5 cm (1.4 in) long and 1.5 cm (0.59 in) broad. The flowers are small, subtended by a pair of conspicuous petal-like bracts, variably red, pink or white, up to 12 mm (0.47 in) broad. Wat Phrik in Thailand claims to be the home of the world’s tallest Christ thorn plant. The plant thrives between spring and summer but produces flowers all year round.
Toxicity
The sap is moderately poisonous, and causes irritation on contact with skin or eyes. If ingested, it causes severe stomach pain, irritation of the throat and mouth, and vomiting. The poisonous ingredients have been identified as phorbol esters. It is very toxic to domesticated animals such as horses, sheep, cats and dogs. For humans it is mildly toxic and only acts as an irritant.
II. How to Grow and Care
Sunlight
When it comes to lighting, Crown of Thorns thrives in bright, indirect light. Place it near a sunny window where it can receive sufficient sunlight without being exposed to direct rays, especially during the scorching summer months. However, do ensure that you provide some shade during the hottest part of the day to prevent leaf burn.
Kumaravel
CC BY 2.0
In its natural habitat, the Crown of Thorns receives intense sunlight, so replicating these conditions as closely as possible will ensure optimal growth. The bright light encourages the plant to produce more flowers, adding to its beauty and charm.
If you’re growing this plant indoors, you can use artificial grow lights or fluorescent lamps to supplement natural lighting. Aim for around 12-14 hours of light per day to promote healthy growth. Remember to adjust the distance between the light source and the plant to prevent burning or scorching the leaves.
Temperature and Humidity
Crown of thorns likes the same room temperature that people enjoy. Temperature-wise, a comfortable 65 to 75 degrees Fahrenheit is suitable. At least half a day of sunlight is a major requirement for crown of thorns. Don’t worry if you lower the thermostat at night; crown of thorns can handle temperatures down to 50 degrees Fahrenheit.
It also doesn’t mind the lack of humidity prevalent in most homes during the winter.
Watering
Watering Crown of Thorns requires a delicate balance. While it is drought-tolerant and can go without water for extended periods, it is essential to provide adequate moisture without overwatering.
Allow the top inch of soil to dry out before watering. Insert your finger into the soil to gauge the moisture level – if it feels dry, it’s time to water. Remember that it’s better to underwater than to overwater this plant, as excessive moisture can lead to root rot.
During the active growing season, typically spring and summer, you can increase the frequency of watering. However, always ensure that the soil has dried out between waterings to prevent the plant from sitting in soggy soil.
In contrast, during the dormant period, reduce watering to keep the soil barely moist. This period usually occurs in late fall and winter when the plant slows down its growth. It’s important to adjust your watering schedule accordingly to prevent the plant from becoming waterlogged.
Soil
TANAKA Juuyoh (田中十洋)
CC BY 2.0
If growing outdoors, plant in well-draining soil. Crown of thorns is a very adaptable houseplant. It needs a well-draining cactus potting mix. The root ball should be snug in a container to discourage the retention of water in the container. If there is excess soil, it will retain water and could cause the roots to rot.
Fertilizing
Feeding your Crown of Thorns is essential for robust growth and blooming. During the active growing season, use a balanced, water-soluble fertilizer with an N-P-K ratio of 10-10-10 or 20-20-20 once every two weeks. Dilute the fertilizer as per the manufacturer’s instructions and apply it to damp soil to avoid burning the roots.
The Crown of Thorns is a heavy feeder, meaning it requires regular nutrient supplementation to support its growth and flowering. The balanced fertilizer provides essential macronutrients like nitrogen, phosphorus, and potassium, as well as micronutrients necessary for overall plant health.
Avoid fertilizing during the dormant period to allow the plant to rest. Resume feeding when new growth emerges in the spring, signaling the start of the active growing season.
Pruning
Protect your eyes, hands, and skin from the sap when pruning this plant. To stop sap from flowing, spray water directly on it. Despite its rows of thorns, crown of thorns is easy to handle if you grasp it by its leafy stems or hold it by its roots.
TANAKA Juuyoh (田中十洋)
CC BY 2.0
Give crown of thorns renewal pruning at the end of the season by cutting away any older, fading leaves to encourage new growth. The crown of thorns may become leggy if it is not pruned to encourage leafy or branching growth. If growing it outdoors, give the plant plenty of room. It can grow up to 6 feet wide and about 2 feet wide.
You will also want to prune crown of thorns to keep a compact shape if it’s a houseplant. Avoid lopping off healthy buds.
Propagation
Most modern crown of thorns are hybrids and are not started from seed; however, they are easy to propagate from cuttings. The best time to propagate cuttings is in the spring when growth begins, but summer is also suitable. Here’s how to propagate from cuttings:
- Wear gloves to limit the amount of sap you come in contact with.
- Using a clean, sharp knife, cut off the top 3 to 4 inches of a healthy, young stem.
- Dip each cutting into warm water and let them sit in it for a few minutes.
- Lay them out to dry and callus over for a few days before planting.
- To encourage faster rooting, coat the cut stem end with rooting hormone.
- Plant the stem in a cactus mix and keep it out of direct sun.
- Place the plant in a warm spot to encourage rooting; a warming mat set to 77 F works best.
- It can take several weeks before the plants take root. New plant growth is a sign that rooting has occurred.
Potting and Repotting
Do not plant in an overly large container. The container should not be over an inch or two larger than the root ball. A crown of thorns houseplant is simple to repot every two or so years if wearing protective gloves and eye gear while potting your plant. Only repot it when it appears to be outgrowing its container.
To repot it, remove the plant from its current pot, loosen the roots, and place it in a new pot that’s only a couple of inches larger. Use cactus potting mix only. Water thoroughly after you have placed the plant in its new home.
Overwintering
Kumaravel
CC BY 2.0
Container-grown crown of thorns can spend the summer outdoors wherever you need color or interest. Bring it inside before nighttime temperatures dip below 50 degrees Fahrenheit.
Pests and Diseases
Crown of Thorns is generally a hardy plant and is not prone to many pests or diseases. However, it’s essential to keep an eye out for common problems such as spider mites, mealybugs, and scale insects. Regularly check the undersides of leaves and stems for any signs of infestation.
If you detect any pests, promptly isolate the affected plant to prevent the infestation from spreading. You can use organic pest control methods like insecticidal soap or neem oil to combat these pests. Follow the instructions on the product label for safe and effective use.
Spider mites are tiny arachnids that can cause damage to the Crown of Thorns plant by sucking the sap from its leaves. They are most commonly found in dry and dusty conditions, so it’s crucial to maintain proper humidity levels and regularly clean the leaves to prevent infestation.
Mealybugs are small, soft-bodied insects that often appear as white, cotton-like clusters on the plant. They feed on the sap of the Crown of Thorns, causing wilting and yellowing of leaves. To control mealybugs, you can use a cotton swab dipped in rubbing alcohol to remove them manually or apply insecticidal soap.
Scale insects are another common pest that can affect the Crown of Thorns. They appear as small, brown or black bumps on the stems and leaves. These pests also feed on plant sap, leading to stunted growth and yellowing of foliage. To eliminate scale insects, you can use a soft brush dipped in soapy water to scrub them off or use commercial insecticides specifically designed for scale insects.
Additionally, overwatering or poor drainage can lead to root rot. Ensure that the soil is well-draining and adjust your watering schedule accordingly to avoid excessive moisture accumulation. It’s best to allow the top inch of soil to dry out between waterings to prevent the roots from sitting in water for too long.
Root rot is a fungal disease that affects the roots of the plant, causing them to become mushy and discolored. To prevent root rot, it’s important to use a well-draining potting mix and avoid overwatering. If you notice any signs of root rot, such as a foul smell or blackened roots, you may need to repot the plant and trim away the affected roots.
III. Uses and Benefits
John Rusk
CC BY 2.0
There are some places where it is regarded as a weed, but it can be used medicinally. Crown of thorns is a very fast-growing plant, and it has very sharp thorns on its stem. These plants have been used for centuries as antiseptics, painkillers, disinfectants, and tonics.
The plant itself has proven to be an effective molluscicide and a natural alternative to pest control. The World Health Organization (WHO) has recommended the usage of Euphorbia milii in aiding snail control. Especially in endemic countries. Schistosomiasis is an infectious disease from freshwater parasites, carried by snails. Extracts from the plant are used to control the snail population to avoid getting infected from a parasite.
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