Cultivation Methods and Care Tips for Crown of Thorns

Crown of Thorns is also known as Iron Begonia, Qilin Thorn, and Qilin Flower. It originates from the island of Madagascar in Africa. It prefers a warm, humid environment with plenty of sunlight. It tolerates high temperatures but not cold. A loose, well-draining leaf mold soil is best. In winter, the temperature should not drop below 12°C. For potted plants, repot every spring, and do not water excessively. During the growing season in summer and autumn, it needs ample water, and should be fertilized once a month. When winter temperatures are low, the leaves drop and the plant enters dormancy, so the soil in the pot should be kept dry. The flowering period runs from March to December; keeping soil moisture moderate will allow continuous blooming. If the indoor temperature in winter stays above 15°C, it can continue to flower. When the plant becomes too crowded and dense, the whole plant can be pruned in spring before new leaves emerge.

Crown of Thorns has a peculiar nature: it grows slowly, adding only about 10 cm per year, but it is long-lived and can survive more than 30 years as a potted plant. Its flowering period is long; if light and temperature are suitable, it can bloom year-round. The branches of Crown of Thorns do not branch easily, so they grow very long, produce few flowers, and look messy, which affects its ornamental value. Therefore, it must be pruned and pinched back promptly every year to encourage more new branches and more flowers. Generally, after a branch is pinched back, it can produce two new branches. Crown of Thorns has a well-developed root system and grows vigorously. It can be used as a rootstock for grafting Christmas cactus and crab claw cactus, but it is a shallow-rooted plant, with roots that spread far horizontally while having few root hairs.

Crown of Thorns likes warmth and cannot tolerate cold. It grows best at around 22°C during the day and around 15°C at night. In a greenhouse kept at 15°C to 20°C, it can bloom continuously all year. If the temperature drops to 10°C, it sheds its leaves and enters a semi-dormant state, then in the following spring it sprouts new leaves and continues to bloom. Crown of Thorns loves light. The more abundant the sunlight before flowering, the more vivid and eye-catching the flowers and the longer they last. With insufficient light, the flower color becomes dull; if kept in shade for a long time, it will not bloom. Also, be sure to maintain air circulation. Crown of Thorns can be given a base fertilizer of hoof and horn pieces placed under the potting soil, and during the growing season it should be fertilized once every half month. Stop fertilizing after the Start of Autumn, and avoid oily fertilizers to prevent root rot. Crown of Thorns is drought-tolerant. In spring and autumn, water according to the principle of watering when dry and stopping when wet. In summer, water once a day; in the rainy season, guard against waterlogging. In winter, do not water unless the soil is dry, and do not keep the pot moist for long periods. Watering should also be controlled during the flowering period, as too much water can easily cause flower drop and root rot.

The main diseases are stem blight and rot. Spray with 50% captan at 800 times dilution once every half month. Pests include whiteflies and scale insects; spray with 50% fenitrothion emulsifiable concentrate at 1500 times dilution to kill them.