The Cathedral Cactus, Euphorbia trigona, is a popular succulent often mistaken for a true cactus due to its tall, spiny, and columnar appearance. Originating from Central Africa, it is also called the African Milk Tree. This sought-after houseplant has a unique architectural form and low maintenance requirements, making it an excellent choice for many indoor and outdoor settings.
Essential Care for Your Cathedral Cactus
The Cathedral Cactus thrives in bright, indirect sunlight, needing at least four to six hours daily. While it tolerates some direct morning or late afternoon sun, excessive direct sunlight can scorch its leaves and stems. For indoor placement, a south or west-facing window is ideal. Leggy growth or pale coloration indicates insufficient light; supplemental grow lights can help.
Watering the Cathedral Cactus requires a “soak and dry” approach to prevent root rot. Allow the soil to dry out completely between waterings, checking the top inch or two. During the active growing season (spring and summer), water weekly. Reduce this significantly to once every four to six weeks in dormant fall and winter. Overwatering is more detrimental than underwatering.
A well-draining soil mix is crucial. A commercial cactus or succulent potting mix is suitable, or create your own by combining potting soil with perlite or coarse sand for enhanced drainage. Soil pH should range from 6.1 to 7.8. Adequate drainage holes in the pot are essential to prevent water accumulation.
The African Milk Tree prefers warm temperatures, thriving between 65°F and 85°F (18°C to 29°C). It is not frost-tolerant and needs protection from temperatures below 40°F (4°C). This plant adapts to average household humidity and does not require misting. Avoid cold drafts, as they stress the plant.
Fertilizing is beneficial during the active growing season. Apply a balanced, low-nitrogen or cactus-specific fertilizer, diluted to half strength, monthly. During fall and winter dormancy, cease fertilization entirely to prevent salt buildup, which can harm roots.
Repotting Your Cathedral Cactus
Repotting is needed every two to three years, or when the plant shows signs of being root-bound (stunted growth, roots from drainage holes). Spring or early summer are ideal times. Gently loosen the root ball with a dull knife to separate the plant from its old container.
Choose a new pot one size larger. Clay or terracotta pots are preferred for better airflow and quicker soil drying. After placing the plant, fill around the roots with fresh, well-draining succulent or cactus mix. Pat it down to secure the plant. Water sparingly immediately after repotting, allowing the soil to dry completely before the next watering to reduce stress.
Propagating Cathedral Cactus
Propagating the Cathedral Cactus is done through stem cuttings. Take cuttings during late spring or early summer using a clean, sharp knife or pruning shears. Cuttings should be at least 4 to 6 inches long.
Allow the severed end to “callus” or dry for three to seven days before planting. This callusing prevents rot. Plant the cutting one to two inches deep into a small pot with well-draining succulent or cactus mix. Place the cutting in bright, indirect light and water sparingly until roots form, which can take several weeks.
Troubleshooting Common Issues
Overwatering is a frequent problem, leading to mushy stems, yellowing leaves, and root rot. If detected early, reduce watering frequency and ensure the soil dries out thoroughly. In severe cases, repotting into dry, well-draining soil and trimming any rotted roots may be necessary.
Underwatering can cause stems to shrivel or wrinkle, and leaves may become crispy. Increase watering frequency to allow for thorough saturation when the soil is completely dry.
Yellowing leaves can also indicate insufficient light, leading to leggy, stretched growth and pale coloration. Move the plant to a brighter location or provide supplemental light.
While generally pest-resistant, Cathedral Cacti can occasionally encounter spider mites or mealybugs. Spider mites cause dusty appearances or tiny webs; mealybugs appear as small, cotton-like clusters. These pests can be managed with insecticidal soap or neem oil.
Handling Your Cathedral Cactus Safely
The Cathedral Cactus produces a milky white sap (latex) when its stems or leaves are damaged. This sap can irritate skin and eyes, and is toxic if ingested. Contact can cause skin irritation, rashes, or blistering. If sap contacts eyes, it can cause severe irritation, including conjunctivitis and, in extreme cases, temporary blindness.
Wear protective gloves and eye protection when handling or pruning to avoid sap contact. After any contact, thoroughly wash hands with soap and water. To prevent accidental exposure, place the Cathedral Cactus out of reach of children and pets.