What to Do When Crown of Thorns (Christ Thorn) Leaves Turn Yellow and Curl? A Summary of Solutions

Crown of thorns, also known as Christ thorn or iron begonia, is a vine-like plant with spiny edges. Although its edges bear thorns, this does not diminish people's affection for it at all. During the cultivation of crown of thorns, yellowing and curling of the leaves is quite common. Below is a brief summary of solutions for yellowing and curling leaves of crown of thorns, for everyone's reference.

I. Causes of yellowing and curling leaves in crown of thorns

1. Too much watering: Crown of thorns has fleshy stems and leaves, is not afraid of drought, but fears waterlogging. Too much watering will damage the root system, causing leaves to turn yellow and drop.

2. Too much fertilizer: Crown of thorns does not like fertilizer. During cultivation, if too much fertilizer is applied or unfermented raw fertilizer is used, it will burn the root system and cause leaves to turn yellow.

3. Poor air circulation: Crown of thorns has certain requirements for its surrounding growing environment and is best suited to well-ventilated, airy places, so it is generally planted more in courtyards and on balconies. If indoor ventilation is poor and it is relatively stuffy and hot, it will cause the leaves of crown of thorns to turn yellow.

4. Chemical damage: When watering crown of thorns, if tap water is used, it should be left to stand for a few days first. Otherwise, the chloride in the water is toxic to the plant, causing the leaves of crown of thorns to turn yellow and drop.

5. Winter dormancy: In late autumn, while crown of thorns enters its peak flowering period, it is also about to enter its winter dormancy period, so yellowing leaves are normal. Even if all the leaves drop, new leaves will sprout again in spring.

6. Temperature too low: In regions where winter temperatures fall below 10 degrees, the old leaves of crown of thorns will drop, leaving only the tender leaves at the top; when the temperature is even lower, the leaves will all dry up and drop.

II. Solutions for yellowing and curling leaves in crown of thorns

1. Soil changes causing curling and yellowing leaves

Solution: For growing crown of thorns, loose, well-drained leaf mold is best. Do not use sea sand or river sand from saline-alkali areas, as they are not suitable for the growth of flowering plants.

2. Overwatering causing yellowing and curling leaves

Solution: Crown of thorns is a succulent plant and is drought-tolerant, so it should not be watered too much. If the potting soil stays too wet for a long time, it will not only cause root rot but also endanger the plant's survival. Therefore, normally water so that the potting soil stays slightly dry. In summer, water evaporates quickly, so watering should be appropriately increased, but there must be no water accumulation in the pot. Too much watering during the flowering period will cause flowers and buds to drop, and may even cause root rot.

3. Insufficient sunlight causing curling and yellowing leaves

Solution: Crown of thorns likes plenty of sunlight and should be given relatively sufficient light throughout the year. During the flowering period, with ample sunlight, the bracts are brightly colored and the flowering period is long; with insufficient sunlight, the flower color is dull, and if kept in shaded conditions for a long time, it will not bloom or will bloom very little. Crown of thorns likes warmth and is not cold-tolerant. In northern regions, it is generally taken outside in early May and placed in a sunny spot, then brought indoors in early October and placed in a spot indoors with sunlight. In summer, keeping it in a semi-shaded place, or shading it by 50{bf}, will make the leaf color more beautiful. In spring and autumn, since the temperature is not very high, it should be given direct sunlight to help it carry out photosynthesis and accumulate nutrients. In winter, keep it indoors in a place with bright light. If it is normally kept indoors, it should be placed near southeast-facing doors and windows so it can receive light, and every one month or one and a half months, it should be moved outdoors for two months of care.

4. Temperature too low causing curling and yellowing leaves

Solution: During overwintering, when the room temperature is low, the leaves will drop completely and the plant will enter a semi-dormant state. At this time, watering must be strictly controlled and the potting soil kept dry. When the temperature is below 0°C, the plant will die from freeze damage. If the indoor temperature in winter can be kept above 15°C, it will bloom continuously throughout the winter. Crown of thorns is very suitable as an indoor flower for autumn and winter cultivation in the north.

5. Too much fertilizer causing curling and yellowing leaves

Solution: Fertilizer should be applied sparingly. Apply light fertilizer 2~3 times each spring. Fertilization can be reduced in autumn. Crown of thorns does not like strong fertilizer; during the growing season, applying decomposed dilute cake fertilizer water once every 3~4 weeks is sufficient. Too much fertilizer, especially too much nitrogen fertilizer, will cause leggy branches that only grow leaves and do not bloom. Applying phosphorus and potassium fertilizer 1~2 times during the bud stage will result in more flowers and brighter colors.

6. Pests and diseases causing curling and yellowing leaves

Solution: For whiteflies, spray with buprofezin or acetamiprid. For scale insects, if the quantity is small, manual removal is enough.

Warm reminder: Crown of thorns is a vine-like spiny plant in the Euphorbiaceae family. A common feature of Euphorbia plants is that after the plant body is injured, white milky sap is secreted from the wound, which is toxic. The white milky sap secreted from the wounds of crown of thorns and similar plants has an irritating effect on human skin and mucous membranes, and accidental ingestion can cause nausea, dizziness, and so on. It is a beneficial weapon that plants evolved to protect themselves and prevent damage from pests and diseases. For home cultivation, as long as you do not casually break off flowers for children to play with, it will not cause harm. People can use the stem and leaf soaking filtrate of Euphorbia plants to control flower pests such as aphids and red spider mites. Because its sap is toxic, it is best not to keep it as a potted plant indoors; as an outdoor ornamental flower, it is also a very good choice.