The African Milk Tree (Euphorbia trigona), also known as the Cathedral Cactus, is a striking succulent admired for its upright, architectural form. Often mistaken for a cactus due to its tall, spiny appearance, this plant is relatively easy to care for, making it a popular choice for both indoor and outdoor environments.
Euphorbia trigona, commonly known as the African Milk Tree.
Description and Characteristics
Native to central Africa, in countries like Angola, Gabon, and Congo, the African Milk Tree thrives in hot, arid environments. It has adapted to endure long periods of drought. Here are some key features:
- Stems: Tall, upright, and triangular in cross-section.
- Spines: Short, sharp spines along the ridged edges.
- Leaves: Small, teardrop-shaped leaves that grow intermittently.
- Color: Typically green, but some cultivars like Euphorbia trigona ‘Rubra’ have reddish or burgundy hues.
- Height: Can grow up to 10 feet tall in favorable conditions, but indoors, it often reaches about 6 feet.
The African Milk Tree forms a vertical, columnar structure with multiple branching stems and a stout, cylindrical, grey trunk. It is primarily grown for its stunning form rather than its flowers, as it rarely blooms in cultivation, especially indoors. When it does flower, the blooms are small, inconspicuous, and yellow or white, typically appearing in the summer months.
Ideal Growing Conditions
Caring for an African Milk Tree is straightforward, similar to caring for a typical cactus. The main concerns are light, watering, and soil conditions.
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Light
African Milk Tree requires abundant, bright and direct light. The African Milk Tree thrives in bright, indirect sunlight, but it can also tolerate direct sunlight in the morning or late afternoon. Place it less than one foot from a window to ensure it receives enough light to survive 💪. When grown indoors, placing it near a south-or west-facing window is ideal, as it can get ample light throughout the day. If the sun in your sunniest window is not adequate, artificial lights should be considered, alone or in combination with natural light. Artificial light is not equivalent to daylight in strength and must be delivered for at least 14 to 16 hours per day. The stems and branches are dark green which becomes brighter with more light. Exposure to a dramatic shift in light can cause limbs to sunburn and die back. This injury can happen if a plant is moved outdoors to strong direct sunlight or without a period of transition. Even a very bright interior window allows much less light transmission that direct outdoor sun. Exposing the plant to increasing hours of light over a period of a week to ten days will allow the plant to adjust and enjoy the new location.
Watering
African Milk Tree thrives in dry soil and should be watered sparingly. As a succulent, the African Milk Tree requires well-draining soil to prevent root rot. The African Milk Tree is highly drought-tolerant, but proper watering is essential to keep it healthy. Water your plant to make all the potting mixture just moist with tepid water, then allow it to drain completely through the drain hole before removing the run-off water. The soil should nearly dry before you water it again. It’s better to err on the side of underwatering than overwatering. Overwatering is a likely cause of issues with African Milk Tree. If the soil is allowed to stay too wet, it can kill the plant. The African Milk Tree is drought-tolerant and can go for several weeks without water. Leaf drop indicates that the plant is under significant stress and often involves issues occurring at the roots of the plant. These damp soil injuries can lead to plant death if not corrected quickly.
Begin to taper the watering frequency in fall as days get shorter. Typically, in the low-light conditions of fall and winter (October through February), water only as often as is necessary to prevent your plant from slight wrinkling.
Soil
African Milk Tree is very sensitive to wet soil, so choose a potting soil that drains very well and doesn’t retain too much moisture. As a succulent, the African Milk Tree requires well-draining soil to prevent root rot. A commercial cactus or succulent mix is ideal. You can also create your own mix by combining potting soil, perlite, and sand for better drainage. A good soil will have lots of perlite or vermiculite for drainage and some organic matter for nutrition. Moisten the soil in the plant's container before attempting to remove it to loosen the growing medium. Take your time and be gentle. The root system is delicate, and you want it to remain as intact as is possible.
Temperature and Humidity
African milk trees are happy with the temperature conditions achievable in New York area households. The African Milk Tree prefers warm temperatures and can thrive in conditions ranging from 65°F to 85°F (18°C to 29°C). Daytime temperatures of 65 to 90° F. and nighttime temperatures ranging from 60 to 75° F. While it can tolerate brief drops in temperature, it is not frost-hardy and should be protected from temperatures below 40°F (4°C). Like other succulents, they will benefit from a slight temperature dip from day to night in order to grow most successfully. A decline in temperature during the winter months helps the plants to adjust to decreasing hours of sunlight. A winter rest at approximately 55° F. As for humidity, this plant prefers low to moderate humidity and is well-adapted to dry air. African milk trees do not need humidity to prosper, and misting is not advised. The African Milk Tree is hardy in USDA zone 9-11 and can tolerate temperatures down to 27°F (-3°C) for short periods.
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The African Milk Tree can be grown outdoors in USDA Hardiness Zones 9a-11b.
Fertilizing
African Milk Tree grows very slowly and doesn’t require added fertilizer. Minimal nutritional intervention is required. Succulents should be fed only during their growing season (March through September). A cactus or houseplant food, fed at half strength, three or four times per growing period is fine. Replacing your plant’s potting soil once a year should provide them with more than enough nutrition. It is important to differentiate the non-active growth period of your Euphorbia and to give it a rest.
Pruning
African Milk Tree Propagation - How to get your cutting and root it in soil successfully
Repotting
To replenish this plant's nutrients, repot your African Milk Tree after it doubles in size or once a year-whichever comes first. While it is young and growing most rapidly, move your plant up one pot size each spring. A terracotta pot with a drain hole and without glazing helps to maintain a healthy root system. Do not re-pot this plant into a container that is larger than necessary for its root system or extended soil moisture from too much soil can lead to root damage. A terracotta container with a drain hole and a run off dish that is emptied after watering. These damp soil injuries can lead to plant death if not corrected quickly. Examine the roots and stem of the plant gently looking for healthy, firm tissue.
Propagation
To propagate this plant, you can take a 5-inch stem cutting in late spring or early summer. African milk tree should not be rooted in water or it will rot. The timing is important. The plant is in more active growth at this time and the long daylight hours and dry warmth support faster rooting. Protect your skin and eyes when making cuttings, as the sap can cause serious irritation or an allergic reaction. Stopping the flow of milky sap is important to the health of the parent plant and the cutting. Dip the cutting end in water and spray the parent's wound with water. Then let the cutting dry out ("callus") in a warm, dry space before planting. This plant may sometimes take a month or more to callus because the stems can be thick. The dampness of the weather, type of heat in your home and amount of air circulation will all have an impact on timing. Prepare a pot of moistened potting mixture, with added perlite for better drainage (or a cactus and succulent potting mix without added fertilizer), and a layer of horticultural sand or vermiculite on top to prevent rot. Insert your cutting into the potting mix and place it in filtered light at a room temperature of about 70 degrees. Keep the potting mixture just barely moist for two to six months.
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Common Issues and Solutions
Here are some common issues you might encounter while caring for your African Milk Tree and how to address them:
- Overwatering: Is a likely cause of issues with African Milk Tree. Cut your plant just past where the rot ends and allow it to callus over for a few days before replanting it in fresh, dry soil.
- Leaf drop: The leaves are a bit of a luxury for this plant which drops them naturally as they age but also when under even slight stress. It will grow and keep more of them when all of its environmental needs are met. These environmental factors can be easier for a plant to recover from if adjustments are made in time. Do not make too many significant changes all at once or the plant will become further stressed. Instead, ease the plant from the current environment to a more appropriate setting.
- Suddenly browning branch ends: Occur when the plant is exposed to cold temperatures. This can happen when it is left outdoors in the cold, in a cold draft from a window or air conditioning vent, or from a cold micro-climate near a window in winter. While the brown parts have died, the plant may recover. Return the plant to the proper bright, steady environment and let it stabilize for a day or two. If there is any green remaining on the plant, follow the pruning instructions above taking care to protect yourself and using sterile tools. Cut off each of the brown sections until you hit live, green growth. The plant may or may not recover depending upon its state of health before the injury, the extent of the damage and the time of year it takes place.
- Brown, bark-like changes to the color and texture of the trunk base: Is natural.
- Mealybugs and scale insects: Look for small, cotton-like clusters or brown, raised bumps on the stems.
- Spider mites: If the plant appears dusty or has tiny webs, it may be infested with spider mites.
- Leggy Growth: If your African Milk Tree starts to grow tall and spindly, it may not be getting enough light.
- Yellowing Stems: This can be a sign of overwatering. Ensure the soil is completely dry before watering again.
- Sunburn: If the stems turn brown or red in patches, the plant may be getting too much direct sunlight.
Common issues with African Milk Tree can be addressed with proper care.
Toxicity
African Milk Tree is extremely dangerous if consumed. This plant leaks toxic, milky latex that flows from a wound and can cause traumatic skin and mucus membrane irritation. Take care to use gloves and protective eyewear when working with the plant. Protect your skin and eyes when working with the plant as the sap can cause irritation or an allergic reaction. Protect your eyes, skin and clothes from the white latex-like sap. This sap can cause skin and eye irritation which can sometimes be severe. It will also stain your clothes and become black when it dries. Also, because of this sap, these plants are not good for composting. If you, a family member, or a pet has ingested any amount of plant material contact Poison Control, US (800) 222-1222, or your veterinarian immediately. No, the African Milk Tree is not edible. No, the African Milk Tree is toxic to dogs. If ingested, it can cause vomiting, diarrhea, or other symptoms.
By following these guidelines, you can ensure your African Milk Tree thrives and remains a stunning focal point in your home or garden.
