The Crown of Thorns (Euphorbia milii), a striking succulent from Madagascar, is a popular choice for bonsai. Its appeal stems from its woody, thorny stems and vibrant, long-lasting “flowers” that can bloom almost year-round. These colorful bracts, modified leaves surrounding the small true flowers, come in shades of red, pink, white, and yellow, adding a distinctive splash of color to any bonsai collection.
Caring for Your Crown of Thorns Bonsai
Maintaining a healthy Crown of Thorns bonsai requires attention to its specific environmental needs, similar to many succulents.
Light Requirements
Crown of Thorns thrives in abundant sunlight, ideally receiving at least 4 to 6 hours of direct sun daily. This light exposure encourages robust growth and prolific flowering. In extremely hot climates, some midday shade can prevent leaf scorching and promote better blooms.
Watering Practices
As a succulent, the Crown of Thorns stores water in its stems, making it highly drought-tolerant. Overwatering is a common problem that can lead to root rot, so it is essential to allow the soil to dry out almost completely between waterings. Water thoroughly until water drains from the bottom of the pot, then wait until the top inch or two of soil feels dry before watering again. During winter or periods of dormancy, reduce watering frequency significantly.
Soil Mix
An ideal soil mix for Crown of Thorns bonsai is fast-draining and gritty, similar to mixes used for cacti and other succulents. This type of mix prevents waterlogging and promotes healthy root development. Components often include pumice, perlite, coarse sand, and a small amount of regular potting soil to ensure excellent drainage and aeration.
Temperature and Humidity
Crown of Thorns prefers warm temperatures, thriving in ranges between 60°F and 80°F (15°C and 27°C). It is not tolerant of frost; temperatures below 50°F (10°C) can cause damage. Average household humidity levels are suitable, as the plant prefers dry conditions.
Fertilization
During its active growing season, from spring to early fall, the Crown of Thorns benefits from regular fertilization. Use a balanced liquid fertilizer or one slightly higher in phosphorus to encourage blooming. Dilute the fertilizer to half strength and apply every four to six weeks. Reduce or stop feeding entirely during the winter months when the plant’s growth naturally slows.
Bonsai Training and Pruning
Shaping a Crown of Thorns into a bonsai involves specific techniques. Patience and careful handling are important due to its brittle nature and milky sap.
Shaping and Branch Pruning
Pruning is essential for developing ramification, which means encouraging finer branching to create a dense, tree-like form. Remove leggy growth and selectively prune branches to promote a more compact structure. The best time for significant pruning is after a flowering cycle or in early spring when new growth begins. Always wear gloves and eye protection when pruning, as the plant produces a white, milky sap that can irritate skin and eyes.
Wiring Techniques
Wiring can be used to shape branches, but caution is necessary because the stems of Crown of Thorns can be brittle. Apply wire carefully to avoid damaging or scarring the bark. Alternative shaping methods, such as the “clip-and-grow” technique, where branches are pruned to direct future growth, can be effective and minimize the risk of damage. This plant’s natural tendency to grow new shoots from pruned areas makes clip-and-grow a suitable approach.
Flowering Considerations
Pruning can impact the plant’s flowering potential, as blooms primarily occur on new growth. To balance aesthetic shaping with continuous flowering, consider pruning after a flush of blooms has faded. This timing allows the plant to produce new growth that will then develop flowers. Ensuring sufficient light exposure is also key to encouraging consistent and abundant flowering.
Repotting and Root Management
Repotting is necessary for maintaining the health and vigor of a Crown of Thorns bonsai.
Crown of Thorns bonsai requires repotting every one to three years, depending on growth rate and root-bound status. Carefully remove the plant, inspect the root system, and prune any circling or overly thick roots, aiming to remove about one-fourth of the root mass while leaving smaller, fibrous roots intact. Replant in fresh, well-draining succulent or bonsai soil, ensuring adequate drainage holes. Handle gently to avoid damaging sensitive roots and stems. After repotting, allow the soil to settle and provide a thorough initial watering.
Troubleshooting Common Problems
Understanding common problems and their solutions can help maintain Crown of Thorns bonsai health.
Yellowing leaves are a sign of either overwatering or nutrient deficiency. Check soil moisture first; if consistently soggy, reduce watering to prevent root rot. If dry, consider a balanced fertilizer application, as nutrient deficiencies can also cause yellowing.
A lack of flowering indicates insufficient light, incorrect fertilization, or pruning at the wrong time. Ensure the plant receives ample direct sunlight and is fertilized during the growing season. Pruning too heavily or at the wrong time can remove developing flower buds.
Common pests such as mealybugs, spider mites, and scale insects can affect Crown of Thorns. Inspect the plant regularly for signs of infestation and treat with organic solutions like insecticidal soap or neem oil.