The crown of thorns, with the scientific name Euphorbia milii, are also called Christ plants or Christ thorns, and are native to Madagascar. These flowering plants of the family Euphorbiaceae are popular ornamental houseplants. They thrive in warmer climates and, like most plants, may also be susceptible to conditions that cause yellowing leaves.
Crown of thorns leaves turning yellow: What are the common reasons?
Insufficient light
Crown of thorns plants thrive in areas with good light. If they do not get enough light, the leaves tend to turn yellow and become droopy. This is indicative of weak growth.
To fix this issue, provide at least four to six hours of bright direct light for your plants. If the plants are kept indoors, make sure that sufficient light can reach them through the windows. You may also provide grow lights for your indoor plants.
Underwatering
Crown of thorns leaves could turn yellow due to underwatering. If the plants become dehydrated, the leaves will become droopy as well as turning yellow.
Make sure that you water the plants weekly, especially during the warmer months and when the soil looks completely dry. During cold weather, water them less, unless they are grown indoors. Allow the soil to dry off before watering the plants again. By checking the soil’s dryness before watering, you can also prevent overwatering your plants.
Temperature issues
Crown of thorns plants thrive in warm climates, and cold temperatures may result in damage such as yellowing leaves. These plants can tolerate temperatures as low as 30 degrees Fahrenheit, but any lower than that could spell danger for them.
If the weather gets too cold in your area, bring the plants indoors to protect them from the frost and chilly weather.
Nutrient deficiency
Crown of thorns leaves turning yellow could also be attributed to nutrient deficiency. If plants do not get the nutrients they need, they tend to turn yellow and start to wilt.
Make sure you provide the necessary nutrients, like chelated iron and phosphorus, to ensure the healthy growth of the plants.
How to prevent crown of thorns from turning yellow
- If you are living in a four-season country, move your plants according to the time of the year.
- Water the plants weekly, but reduce this frequency when the weather gets cold.
- Do not add fertilizers during the winter months, and prepare your plants for the next year’s blooming season.
- Use the right kind of potting soil so that the plants will never sit in stagnant water. It should provide ample drainage for the root system. Adding pumice, sand and perlite to the soil can help with drainage.
- Add liquid and slow-release fertilizer during the planting period.
Why do crown of thorns leaves turn brown?
Crown of thorns leaves usually turn brown because of sunburn. These plants can get burned by the sun’s rays if they are exposed to full sun all day, especially during very warm weather. Young plants should be acclimatized slowly to the light so they are not overwhelmed, and to avoid brown leaves. If the leaves have already turned brown, they will not return to their normal color and you will have to wait for new growth.
Root rot due to overwatering can also turn leaves brown. Hold off watering the plants for a while until the soil has completely dried out. If you notice root rot, remove the rotted roots, keep the healthy ones and repot the plants.
Pest infestation could also be the culprit if your crown of thorns’ leaves are turning brown. Scale insects could invade the plants and cause serious damage if not treated promptly. To eradicate these pests, remove them using a Q-tip dipped in rubbing alcohol. Spray neem oil on the plants to keep the insects away. Repeat the process until there are no more visible traces of these pests.
Conclusion
Crown of thorns plants are dainty succulents that bloom year-round, even when grown indoors. They are also prone to issues that cause yellowing leaves, and these may include insufficient water, temperature issues, lack of light and nutrient deficiencies.
Image: istockphoto.com / Chaidira