Gardening Plants & Flowers Perennials

How to Grow and Care for Crown of Thorns (Euphorbia milii)

A Unique Succulent With a Biblically-Inspired Name

Crown of thorns plant with red flowers with thick bright green leaves

The Spruce / Gyscha Rendy

Crown of thorns, also commonly known by its scientific name Euphorbia milii, is a pretty but thorny succulent tropical shrub. One of its typical characteristics is that it can bloom in many colors with thick, bright green leaves almost year-round, even indoors. This slow-growing plant can reach 3 to 6 feet tall outdoors or 2 feet as a houseplant.

Crown of thorns grows best outdoors as a perennial in warm zones 9 through 11. Grow it indoors in other zones by placing it in a sunny window with at least three to four hours of direct sunlight in well-draining cactus-type soil.

Crown of thorns is toxic to humans and pets. A potential benefit of its toxic sap is being researched for its ability to kill snails that carry disease.

Common Name Crown of thorns, crown-of-thorns, Christ plant, Christ thorn
Botanical Name  Euphorbia milii
Family Euphorbiaceae
Plant Type Succulent 
Mature Size 3-6 ft. tall outdoors, 2 ft. tall indoors; 18-36 in. wide
Sun Exposure Full, partial 
Soil Type Well-drained
Soil pH Neutral to acidic
Bloom Time  Spring, summer, fall, winter
Flower Color  Red, orange, pink, yellow, white
Hardiness Zones  9-11 (USDA)
Native Area  Africa
Toxicity  Toxic to people and pets

Crown of Thorns Care

Here are the main care requirements for growing a crown of thorns plant:

  • Prefers temperatures in the 65 to 75 degrees Fahrenheit range and requires no particular humidity.
  • Handles indoor growth well when in a bright window.
  • Needs well-draining soil.
  • Give water when the soil becomes dry 1 inch past the soil line.
  • Requires fertilizer from spring to fall to encourage more prolific flowering.
Crown of thorns plant red flowers and thorns on single stem
The Spruce / Gyscha Rendy
Crown of thorn plant with stems of thorns and bright green leaves
The Spruce / Gyscha Rendy
Crown of thorn plants with thorns on stems and red flowers
The Spruce / Gyscha Rendy
Crown of thorn shrub with woody stems and red flowers with yellow centers
The Spruce / Gyscha Rendy
Crown of thorns branch with red flowers and leaves closeup
The Spruce / Gyscha Rendy

Light

As with most flowering plants, the better the sun exposure, the more blooms you will get. Euphorbia milii needs direct sunlight, and it will reliably bloom if it receives at least three to four hours of bright sunlight daily. Outdoors, place it in a full-sun location. Place it in a partial sun spot if it's an intensely dry location. Indoors, the plant will do well in a west or south-facing spot during winter.

Soil

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. 

Water

Since it is a succulent, crown of thorns is very forgiving about water. Water when the soil feels dry about 1 inch below the surface. Water thoroughly and allow any excess to drain off. Do not let your plant sit in water or wet soil for prolonged periods, or the roots will rot. Crown of thorns will go semi-dormant in the winter and need less frequent watering and no food.

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.

Fertilizer

From spring through fall, feed your crown of thorns with a balanced houseplant fertilizer. You can do this every other time you water if you dilute the fertilizer to half-strength.

Types of Crown of Thorns

Crown of thorns plants come from the tropics of the African island of Madagascar. The plant's name is derived from the belief that this plant's stems formed the crown of thorns worn by Jesus Christ at his crucifixion. In Thailand, the plant is considered lucky for its auspicious eight flowers growing per stem, representing the eight saints of Chinese mythology.

Local nurseries generally only carry a few varieties. Mail-order catalogs are a good place to look for unusual hybrids, including:

  • 'Brush Fire': Thick, fleshy leaves and bright red flowers
  • 'Creme Supreme': Strappy leaves and creamy white flowers
  • 'Short and Sweet': Red flowers (dwarf, reaching 12 to 18 inches tall)
  • 'Maxi Zephyr': Apricot-colored bell-shaped blooms
  • 'Maxi Pink Cadillac': Coral-pink blooms
  • 'Red Gundula': Pinkish-red blooms
  • 'Splendens': Red blooms but grows tall to 5 or 6 feet
  • California hybrids are bred for thick stems and large flowers. They are sometimes labeled Giant Crown of Thorns. Two good outdoor cultivars are 'Rosalie' and 'Saturnus.'

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.

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 tall 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.

Propagating Crown of Thorns

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:

  1. Wear gloves to limit the amount of sap you come in contact with.
  2. Using a clean, sharp knife, cut off the top 3 to 4 inches of a healthy, young stem. 
  3. Dip each cutting into warm water and let them sit in it for a few minutes.
  4. Lay them out to dry and callus over for a few days before planting.
  5. To encourage faster rooting, coat the cut stem end with rooting hormone.
  6. Plant the stem in a cactus mix and keep it out of direct sun.
  7. Place the plant in a warm spot to encourage rooting; a warming mat set to 77 F works best.
  8. It can take several weeks before the plants take root. New plant growth is a sign that rooting has occurred.

Potting and Repotting Crown of Thorns

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

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.

Common Pests & Plant Diseases

Most pests steer clear of the plant; however, common houseplant pests like scale, mealybug, and thrips may be a problem.

Watch for fungal diseases such as botrytis, leaf spotting disease, and root rot, even if the plant is indoors. Allowing the soil to dry before watering again will help avoid these problems.

How to Get Crown of Thorns to Bloom

Bloom Months

Crown of thorns can bloom every month of the year, depending on its care needs being met.

How Long Does Crown of Thorns Bloom?

Crown of thorns blooms year-round. It will repeat bloom throughout the year if given fertilizer spring through fall, ample sun, and moderate watering.

What Do Crown of Thorns Flowers Look and Smell Like?

The true flowers are small and green centers, surrounded by showy bracts that look like colorful petals in red, orange, pink, yellow, or white. They do not have a fragrance.

How to Encourage More Blooms

Crown of thorns prefers direct sunlight and will reliably bloom if it receives at least three to four hours of ample sunlight daily. However, the plants will appreciate mid-day shade in overly dry climates to encourage better blooms.

Common Problems With Crown of Thorns

Although this is a tough plant and easy to grow, you may encounter a couple of problems with crown of thorns that can usually be remedied.

Yellowing Leaves

Crown of thorn leaves should be bright green. If the leaves are yellowing and beginning to fade, it could mean the plant is underwatered. It could also mean the plant is not doing well because of sudden temperature changes, which is especially common with houseplants. Poor soil quality or the wrong mix type could also turn leaves yellow.

Dropping Leaves

Some cyclical leaf drop is expected, especially before winter when the plant rests. However, if the plant is completely stressed due to living in an environment that's too hot or being underwatered, it will shed every leaf. When the source of the stress is eliminated, the leaves will begin to grow back.

Lack of Blooms

If your indoor crown of thorns is not blooming, it may be getting too much light at night (they need total nighttime darkness for best flowering conditions). Poor flowering may also be the result of overfertilizing. Too much fertilizer will produce more foliage than flowers.

Browning Stems or Leaves

Immediately cut off and dispose of any brown parts of your crown of thorns. Brown portions may mean a fungus developed due to prolonged moisture (indoors or outdoors), which rotted parts of the plant.

FAQ
  • Does crown of thorns grow well indoors and outdoors?

    Crown of thorns can grow well as a houseplant or in the garden as a woody shrub in hardiness zones 9-11. It likes the same room temperature that people enjoy and can handle the lack of humidity prevalent in most homes during the winter.

  • Will crown of thorns grow better in sun or shade?

    For the most profuse flowers, put the plant in a full sun spot with at least three to four hours of bright sunlight daily. The plant will grow best indoors in a west or south-facing window.

  • What is the best way to cut back crown of thorns?

    When handling this plant, protect yourself from the sap and thorns with heavy gardening gloves. Prune crown of thorns to prevent legginess and healthy growth, but avoid lopping off healthy buds.

  • Is Euphorbia milii a cactus?

    Crown of thorns is a succulent but not a cactus. It is often confused with a cactus because it is a spiny shrub.

The Spruce uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Crown of Thorns, Euphorbia milii. Wisconsin Horticulture.

  2. Crown of thorns. Pet Poison Helpline.

  3. Euphorbia milii. Henry Shaw Cactus and Succulent Society.