The Crown of Thorns plant, Euphorbia milii, is a blooming succulent that grows into a woody shrub that features sharp thorns on its stems.
The plant’s name has biblical connotations — it’s believed that the crown of thorns worn by Jesus Christ as his crucifixion was made with the stems of this plant.
Because of this, the plant is also known as Christ Plant or Christ Thorn.
If you’re not put off by this story and you want to grow the Crown of Thorns plant indoors, follow my tips below.
Crown of Thorns Plant Care Tips
Adding to the biblical history of the plant the fact that its sap is an irritant and all parts of the plant are toxic to pets, it may sound like a difficult plant to keep indoors.
If you don’t have pets or small children around, as you’ll read below, this plant isn’t difficult to cultivate, produces vibrant blooms, and it’s easy to propagate.
The crown of thorns can grow into a 6 feet shrub if it’s kept outdoors in ideal conditions. Indoors, expect it to reach only ⅓ of its maximum outdoor size.
The crown of thorns plant enjoys full sun exposure outdoors. Indoors, they should receive at least 3 or 4 hours of full sun each day. This will help the plant bloom throughout the year.
The crown of thorns plant is relatively resilient when it comes to watering in the sense that it can tolerate some neglect in this department. Dry indoors aren’t an issue and room temperature is just fine for this plant.
When watering this plant, make sure the soil is thoroughly watered, but also that water drains fast and efficiently, and doesn’t stay in the saucer. Don’t water the plant again until the soil is dry at a depth of about an inch.
This watering regimen will keep the plant thriving and it will keep you from overwatering the plant. Overwatering can cause the roots to rot, which can quickly kill off the entire plant.
Temperature & Humidity
If the temperature in your home is comfortable for you, it will be comfortable for your crown thorns plant as well.
Expressed in values, temperatures between 65-75 °F will be ideal for this plant. Crown of thorns can handle temperatures down to 50 F, but lower than that is not advisable.
When it comes to soil requirements, the crown of thorns is not at all picky. As long as the soil has good drainage, the plant will thrive.
My crown of thorns plant tends to favor a potting mix of 1 part regular potting soil and 2 parts coarse sand. To this I add a little compost to enrich it.
You can also get ready-made potting mixes like those designed for succulents and cacti. This will also work great for the crown of thorns.
Fertilizing is needed from spring to fall. You can use a regular balanced houseplant fertilizer diluted to half-strength. Fertilize every two weeks.
Potting & Repotting
When potting the crown of thorns plant, don’t plant in a container that’s too large. It’s best to pick a container that’s only 1-2 inches larger than the root ball. If there’s too much soil, water retention can be increased, which is something you want to avoid with this plant.
Crown of Thorns Plant Propagation
There are several ways to propagate crown of thorns plants including from seeds. Given that most varieties are hybrids, however, the easiest and simplest way to propagate is from stem cutting.
Scheduling propagation in spring or summer will ensure best results given that cuttings need bright light and warmth.
To ensure a high success rate, choose a stem cutting that’s 2 to 4 inches long, not thicker than your pinky finger, and with new leaf buds or fresh leaves at the tip. Also make sure that the stem cutting is healthy and shows no signs of disease.
To minimize the risk of injury to yourself (the sap of the plant is toxic and an irritant), you should wear gloves when handling the plant or when harvesting stem cuttings for propagation.
Use a sharp blade that has been sterilized with rubbing alcohol to perform a clean cut. Next, you need to slightly dry out the cutting before planting. This is to minimize rotting.
Dab the end of the cutting in rooting hormone, then place it in a paper towel in a dry place. Keep it there for a few days until the end of the cutting seems dry or puckered.
Use the same well-draining potting mix that you use for the mother plant, stick the stem cutting into the soil and secure it firmly in place by pressing the soil around the cutting.
Place the newly potted crown of thorns cutting in a dry, warm place, and provide plenty of indirect sunlight while the cutting is still in its rooting phase.
Different Types of Crown of Thorns
Hybridized crown of thorn varieties are aplenty. Some produce large flowers; others grow smaller and have smaller thorns. If you’re getting a crown of thorns plants for its blooms, buy one that’s already in bloom, so you’ll know exactly what to expect.
Here are some varieties that are worth your attention:
– Short and Sweet Crown of Thorns
A highly ornamental variety that’s considered a dwarf cultivar, this variety doesn’t get any taller than 18 inches. It grows soft spines covered with bright red bracts.
– Mini-Bell Crown of Thorns
Another dwarf cultivar that has a compact growth and produces many small red flowers. If you don’t have the space for a tall crown of thorns, this is a great alternative.
Also known as giant crown-of-thorns series, these cultivars produce large flowers and stout stems. Some of the hybrids in this series include ‘Rosalie’, ‘Vulcanus’, and ‘Saturnus’.
– Brush Fire Crown of Thorns
With rosy red flowers and thick, glossy leaves, this is another cultivar that you should consider for a sunny patio or as an ornamental indoor plant.
– Creme Supreme Crown of Thorns
With creamy white flowers and slightly more elongated leaves and densely spiny stems, this variety is a breeze to care for.
Crown of Thorns FAQs
Even if the crown of thorns plant is known as a low requirement houseplant, there are some key areas to look out for that I discuss in the FAQs below.
When to Prune Crown of Thorns?
If your plant has become unruly, you can prune it back and shape it to a manageable condition. It’s best to schedule any pruning after the plant has finished blooming. Also, make sure to wear thick gloves to avoid any injury from the sap of the plant.
Cut back on lateral branches and spray with cold water to stop the sap from flowing out. Pruning is also a good time to save stem cuttings if you want to consider propagation.
Is the Crown of Thorns Prone to Diseases and Pests?
Crown of thorns plants are fairly resistant to diseases and pests. This doesn’t mean they’re immune to them. If the plant is neglected and suffers from deficiencies in cultivation, problems can and do arise.
Root rot induced by overwatering is a common concern that’s easy to prevent with a correct watering regimen.
If the plant’s environment is too humid and air circulation around the plant is poor, plant mildew and fungal diseases can easily develop.
The plant has a reputation of being resistant to pests, which is true. But a massive infestation among your houseplants can decimate your crown of thorns plant as well. Be proactive and look for signs of mealybugs and aphids to prevent a full blown infestation.
Why are the Leaves of Crown of Thorns Turning Yellow?
The main reason why this happens is overwatering. Stop watering and water only when 50% of the soil is dried out. Make sure your plant is in a warm location with plenty of light and good air circulation.
If the stems are soft and mushy, it may already be too late for the plant as the roots have already become rotten. If there are some healthy stems left, harvest those to start over.
Why is the Crown of Thorns Not Blooming?
Make sure the plant gets enough sunlight. Crown of thorns plants need 3-4 hours of direct sun and plenty of indirect sun to bloom. If you want to encourage blooming, simply use a low nitrogen, high phosphorus plant food.
Crown of thorns plants are resilient and easy to grow. They’re highly decorative, especially the dwarf cultivars that have a compact growth.
Remember that all parts of this plant are toxic to pets, so keep them out of their reach or consider a different plan to keep indoors.
Watch out for overwatering issues, let the soil dry between watering, and make sure the plant gets a few hours of full sun, regardless of whether you’re keeping the plant indoors or outdoors.
These coupled with good ventilation around the plant and well draining soil will ensure a problem free development.