Common Problems With Crown of Thorns and How to Handle Them
Keep your Crown of Thorns healthy by learning to interpret its condition. Our guide helps diagnose issues by addressing care routines and environment.
The Crown of Thorns, or Euphorbia milii, is a resilient succulent prized for its thorny stems and clusters of bright bracts. While this plant is known for being durable and relatively easy to care for, it can display signs of distress when its environmental needs are not fully met. It thrives in conditions that mimic its native Madagascar.
Common Leaf Problems
A frequent issue is yellowing leaves, often traced back to overwatering. When the soil remains saturated, roots are deprived of oxygen, causing leaves to turn yellow and feel soft or mushy. This indicates the root system is struggling to absorb nutrients.
Conversely, yellow and crispy leaves point towards underwatering. If the soil becomes bone-dry for extended periods, the plant conserves resources by shedding its leaves. You may notice the lower leaves yellowing and dropping first as the plant prioritizes new growth.
Temperature fluctuations can also cause leaf drop. As a plant from a warm climate, the Crown of Thorns is sensitive to sudden cold drafts or being placed too close to a heat source. This shock can prompt the plant to shed leaves. Brown, scorched spots on the leaves are a result of sunburn from intense, direct sunlight.
Flowering and Growth Issues
A Crown of Thorns that refuses to bloom is an issue linked to insufficient light. To produce its colorful bracts and flowers, the plant requires at least four to six hours of direct sunlight each day. A south-facing window is an ideal location to provide the light intensity needed for flowering.
Insufficient light can also cause a “leggy” appearance, or etiolation. The stems will appear stretched, with sparse leaves spaced far apart as the plant reaches for a better light source. Moving the plant to a sunnier location will halt this stretched growth and encourage a more compact form.
Fertilizer type also influences blooming. A high-nitrogen fertilizer promotes foliage growth at the expense of flowers. To encourage blooms, use a fertilizer with higher phosphorus content, as this nutrient supports flower production and root development. Switching to a “bloom booster” formula during the growing season can stimulate flowering.
Pest and Disease Management
Common pests include mealybugs, which appear as small, white, cotton-like masses on stems or in leaf axils. These pests can be managed by dabbing them with a cotton swab dipped in isopropyl alcohol. Spider mites are another potential issue, identified by fine webbing and tiny specks on the undersides of leaves, and can be treated with insecticidal soap.
The most serious disease is root rot, a fungal condition fostered by overwatering and poorly draining soil. If a plant is wilting despite moist soil and has yellowing leaves, root rot may be the cause. To confirm, remove the plant from its pot and inspect the roots; healthy roots are firm and white, while rotted roots will be brown and mushy.
To treat root rot, trim away all affected brown, mushy roots with a clean, sharp tool. Repot the Crown of Thorns in a new container with fresh, well-draining cactus or succulent mix. Withhold water for the first week after repotting to allow the cut roots to heal and reduce the risk of the fungus returning.