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Guide to Euphorbia Milii: How to Grow & Care for “Crown of Thorns” Plant

Read our complete guide to Euphorbia Milii for everything you will ever need to know! Tips for growing and caring for “Crown of Thorns”
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Euphorbia Milli 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 Governer of Réunion (Bourbon Island), hence the name Milii.

The Euphorbia Milii has an interesting background and can be found under many different names such as Crown of Thorns, Christ plant, Christ Thorn, and Corona de Cristo or Corona de Espinas in Latin America.

You might find these names quite surprising, especially if you know how beautiful this succulent is. So why is it associated with Jesus’ Crown of Thorns? As it turns out, rumor has it that the crown worn by Jesus Christ was made from Euphorbia Milii stems.

Being a tropical plant, the Crown of Thorns succulent thrives in warm conditions, loves drought, but is extremely sensitive to frost. It is usually grown in a container that can be moved indoors for the colder winter months. If you live in a warm climate, you can grow this semi-succulent outdoors as an ornamental shrub.

This evergreen succulent is so interesting and beautiful that it received the Award of Garden Merit from the Royal Horticultural Society in 1993. It blooms all year and it is low-maintenance, so it is the perfect ornamental flower for gardening beginners and very busy plant lovers.

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Crown of Thorns Live Plant, From Amazon

About Euphorbia Milii

  • Crown of Thorns succulents are winter hardy in USDA Zones 9-11, where they thrive in well-drained succulent soil mix, full sun, and dry-to medium moisture.
  • As most succulents and cacti, the Euphorbia Milii cannot withstand very cold temperatures. So, if the temperatures drop below 35°F (1°C), move this semi-succulent indoors.
  • Wet soil in winter is very dangerous for this drought-loving plant.
  • In very hot summer climates, Crown of Thorns succulents will need midday shade.
  • When grown indoors, Euphorbia Milii succulents will do best with gritty soil and bright light.
  • They don’t mind rocky or sandy soil and soil that’s nutrient-poor and they can withstand long periods without water. It’s recommended to apply the ‘soak and dry’ watering technique to avoid leaf drop and to encourage the flowers to bloom.
  • The easiest way to propagate these thorny succulents is by taking tip cuttings. Wear gloves when you touch the plant because its sap is quite poisonous.
  • As mentioned above, the sticky, latex sap that results from broken stems and leaves can irritate your skin and eyes. If ingested, all parts of the plant are toxic for pets and humans alike and can lead to nausea, vomiting, and other digestive issues.
  • Because of its toxicity, this plant is rarely attacked by pests. On rare occasions, it might be affected by mealybugs, thrips, spider mites, and scale bugs.
  • When the environment is too moist, the Euphorbia Milii can be susceptible to root rot and fungal diseases.
Note the thorns on the stem
Note the thorns on the stem

Euphorbia Milii Features: An Overview

  • Euphorbia Milii, also known as Crown of Thorns, is a broad-leaf evergreen, native to Madagascar.
  • It has fleshy, bright-green leaves, thick sharp black thorns, and tiny flowers that grow in clusters and that are subtended by spectacular red or yellow bracts that look like petals.
  • In their natural habitat, Crown of Thorns succulents grow 5-6 inches (12-15 cm) in height and they tend to sprawl.
  • When grown in outdoor gardens in warm areas like Florida, they grow at 3 inches (7-8 cm) tall, and when grown indoors they are about 2 inches (5-6 cm) tall.
  • The sharp thorns of the Euphorbia Milli cover its stems and branches and are 1-2 inches long (2-5 cm) and its leaves are 2-2 ½ inches long (5-6 cm).
  • The true flowers of the Euphorbia Milli lack petals and sepals and are small and greenish. However, they are subtended by beautiful petal-like bracts.
  • When grown in perfect conditions, the flowers of the Euphorbia Milii will bloom throughout the year, but their blooming season is mainly winter through spring. However, it is quite common for Crown of Thorn succulents grown indoors to bloom from late winter well into fall.
  • Succulents and cacti are amazing plants, and hybrids are even better. As a result, plant hybridizers are always looking for new varieties. To know exactly what you’re getting, look for Euphorbias that are in bloom. Local nurseries and shops will probably sell the common varieties of Euphorbia Milii, but you can find a wide range of unique and unusual hybrids online.
Crown of Thorns Plant
Crown of Thorns Plant

Growing Euphorbia Milii

When grown outdoors, the Euphorbia Milii needs a lot of sunlight and well-draining soil. In extremely hot and dry climates, the plants will need shade as the hot midday sun can burn the leaves.

  • Crown of Thorns succulents are versatile and adaptable houseplants. All they need is a well-drained container that’s just an inch or two larger than the root system. When planted in too much soil, the plants can be susceptible to root rot, especially if the soil is damp for extended periods.
  • To grow happy and healthy, the Euphorbia Milii needs at least half a day of sunlight and a temperature between 65-75 °F (18-24 °C). It is not an issue if the temperatures drop a little at night as this succulent can tolerate temperatures as low as 50 °F (10 °C).
  • As a general rule, Euphorbias that get more sun exposure will have more flowers. But the great thing about this semi-succulent is that it will bloom even with 3-4 hours of direct sunlight per day. If you plan on growing it outdoors and want it to blossom regularly, find a spot that gets a lot of sunlight. Indoors, place it near a south or west-facing window.
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Read: How to Grow Succulents from Seeds

Propagating Euphorbia Milii

Despite its scary thorns, the Euphorbia Milii is a friendly and low-maintenance succulent. Hold it by its roots or by its leafy stems to avoid the thorns and wear gloves if needed.

The great majority of Crown of Thorns succulents found on the market are hybrids. They are rarely propagated from seed, as it is much easier to do it from tip cuttings. To avoid the milky sap that’s quite toxic, make sure you wear gloves. Put the fresh cuttings in lukewarm water and let them hydrate for a few minutes. Put them aside for a few days until they dry out and callus.

Get a nice container with drainage holes and fill it with cacti and succulent mix. You want the soil to be moderately damp. If it’s too damp, the cuttings will rot and if it’s too dry they won’t develop roots. It’s safe to say that when it comes to succulents and cacti, you want to avoid both extremes.

To encourage the rooting process, place the container in a warm place that gets a lot of indirect sunlight. It will take 2 weeks to a month for the Euphorbia to fully establish in the new environment, so you’ll need to be patient.

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Read: How to Propagate Succulents

Watering the Euphorbia Milii

Crown of Thorns succulents don’t need a lot of water as they naturally grow in tropical and sub-tropical regions. Pouring a little water occasionally is perfect and will keep your succulent happy and healthy. The main goal is to get the root system completely hydrated. In-between waterings, make sure you let the top layer of soil dry completely.

Ideally, the roots of the Euphorbia Milii should always be just a little damp otherwise the plant will start to shed its leaves. But you need to be careful because too much water can lead to root rot, so it’s recommended to remove the water from the saucer every time.

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But like most succulents and cacti, the Euphorbia Milii prefers drought instead of too much moisture and hates sitting in in water or wet soil for too long. The best watering technique for the Euphorbia is the ‘soak and dry’ technique that consists of watering the plant thoroughly, removing the extra water from the saucer, and letting the soil dry completely before watering again.

If you want to fertilize it, do it from spring through fall and avoid doing it in winter. Because succulents and cacti don’t need a lot of nutrients in general, the fertilizer should always be diluted to half strength. Over the winter months, the Crown of Thorns will go semi-dormant, so it won’t need as much water.

In Conclusion

If you plan on growing Euphorbia Milii succulents outdoors, choose a sunny location with plenty of room. You don’t want to touch it by accident or to trip over it as you might get hurt. At the end of the growing season, cut away the fading leaves and prune the plant to encourage new growth.

If the temperatures drop below 35°F (1°C)in winter, it’s recommended to grow the Euphorbia Milii in a container. When grown indoors, the Crown of Thorns thrives on a sunny windowsill.

Euphorbia Milii is easy to grow semi-succulent that loves sunlight and is very forgiving. If you have a busy schedule or if you don’t have a lot of gardening experience, this flowering succulent is a perfect choice. But be careful not to touch its sharp thorns and to wear gloves when you touch the plant because the milky sap is an irritant. All parts of the plant are poisonous if ingested, so keep it within a safe distance from children and pets.

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Miruna Secuianu

Miruna is an experienced content writer with a passion for gardening. She is the proud owner of an outdoor rose garden and an indoor collection of tiny succulents. She bought her first succulent 10 years ago - an adorable Echeveria Setosa. Now she owns more than 100 succulents and cacti of different colors, shapes, and sizes. Miruna is a versatile writer and, as you might have guessed, her favorite topic is gardening. Contact miruna@gardenbeast.com

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