The Crown of Thorns (Euphorbia milii) is a popular houseplant known for its vibrant, long-lasting “flowers.” These colorful displays are actually modified leaves called bracts, which surround the plant’s small, true flowers. Consistent blooming requires understanding its specific needs.
Understanding Crown of Thorns Blooming
The “blooms” of the Crown of Thorns are showy bracts, not true flowers, appearing in shades of red, pink, white, yellow, and orange. These colorful bracts are the plant’s main ornamental feature. Euphorbia milii can bloom almost continuously throughout the year when provided with optimal conditions, making it a favored choice for year-round color.
Ideal Environmental Conditions for Blooming
Light
Crown of Thorns plants require abundant sunlight to produce a profusion of blooms. They thrive in bright, direct sunlight for at least three to four hours daily. Placing the plant in a south or west-facing window indoors is often ideal to ensure it receives sufficient light. Insufficient light can lead to sparse blooming or leggy growth. In very hot climates, providing some partial shade during intense afternoon hours can prevent scorching while still encouraging robust flowering.
Watering
Proper watering is crucial for Crown of Thorns, as overwatering can quickly lead to root rot and inhibit blooming. As a succulent, the plant stores water in its thick, spiny stems and is highly drought-tolerant. It is essential to allow the soil to dry out completely between waterings. Check soil moisture by inserting a finger about one to two inches deep; if it feels dry, it is time to water. During the active growing season in spring and summer, watering may be more frequent, while in fall and winter, water sparingly.
Temperature and Humidity
Crown of Thorns plants prefer warm temperatures, typically thriving in a range between 65°F and 80°F (15°C to 27°C). They are sensitive to cold drafts and cannot tolerate temperatures below 50°F (10°C), which can stress the plant and hinder blooming. Avoid placing them near cold windows, air conditioning units, or heat sources that cause sudden temperature fluctuations. The plant tolerates average household humidity levels well and does not require high humidity.
Fertilizing for Flower Production
Fertilizing plays a significant role in encouraging flower production in Crown of Thorns. During the active growing season, from spring through fall, the plant benefits from regular feeding. A balanced, water-soluble fertilizer, such as a 10-10-10 or 20-20-20 NPK ratio, applied at half-strength every few weeks, is generally effective. Some sources suggest a slightly phosphorus-heavy fertilizer or “bloom booster” to maximize flowering. Avoid over-fertilization, especially with high-nitrogen fertilizers, as this promotes lush foliage growth at the expense of bract production. Fertilizing should be reduced or stopped entirely during the plant’s dormant period in winter.
Pruning Techniques to Encourage Blooms
Strategic pruning can stimulate new growth and, consequently, more blooms on your Crown of Thorns. Removing spent “flowers,” or deadheading faded bracts, encourages the plant to direct energy towards producing new ones. Light shaping and trimming of leggy or overgrown stems also promotes a bushier growth habit, leading to more flowering points. When pruning, use clean, sharp shears and exercise caution, as the plant’s milky sap can be irritating to the skin and eyes. Making cuts just above a leaf node can encourage new growth in that area.
Troubleshooting Non-Blooming Plants
If a Crown of Thorns plant is not blooming, common causes include insufficient light, as the plant needs several hours of bright, direct sunlight daily to flower consistently. Improper watering, particularly overwatering, can lead to root rot and inhibit blooming; ensure the soil dries out between waterings. Nutrient imbalances, such as excessive nitrogen, can result in abundant foliage but few bracts, so a balanced or phosphorus-rich fertilizer is preferred. Cold temperatures or sudden changes can also stress the plant and prevent flowering. Providing a short rest period in winter with reduced watering and cooler temperatures can sometimes encourage a more vigorous blooming cycle in the subsequent growing season.