Euphorbia trigona, commonly known as the African Milk Tree or Cathedral Cactus, is a visually striking, fast-growing plant often mistaken for a cactus due to its tall, spiny, and columnar appearance. The African Milk Tree is a striking succulent popular for its upright, architectural form and ability to thrive in both indoor and outdoor environments.
Although its appearance resembles a cactus, Euphorbia trigona is a succulent and not a true cactus. Some of the over 2.000 species of Euphorbia are succulent. Often mistaken for cacti, some succulent Euphorbia are striking and interesting houseplants.
Description
The African Milk Tree features tall, upright stems that are triangular in cross-section, hence its species name “trigona.” The plant has green stems with ridged edges adorned with rows of small, sharp thorns. Each ridge also has small, teardrop-shaped leaves that grow intermittently, adding a touch of softness to the otherwise spiny appearance. In some cultivars, such as Euphorbia trigona ‘Rubra’, the stems and leaves take on a reddish or burgundy hue, further enhancing the plant’s ornamental appeal.
In terms of habit, it forms a vertical, columnar structure with multiple branching stems and a stout, cylindrical, grey trunk. The plant’s most striking feature is its triangular stems, which grow upright and columnar. The stems are fleshy and green, with ridged edges adorned by short, sharp spines. The ridges of the stems also produce small leaves, which are oval or teardrop-shaped. These leaves are green in color, although they may take on a reddish hue in certain varieties.
Origin and Habitat
The African Milk Tree is native to the central regions of Africa, particularly in countries like Angola, Gabon, and Congo. In its native habitat, it thrives in hot, arid environments and is well-adapted to endure long periods of drought.
Read also: Handling African Milk Tree Sap
Flowering
The African Milk Tree is primarily grown for its stunning form and not for its flowers, as it rarely blooms in cultivation, particularly when grown indoors. When it does flower, the blooms are small, inconspicuous, and yellow or white. If grown in ideal conditions and if the plant does bloom, it typically produces flowers in the summer months.
Hardiness
The African Milk Tree is hardy in USDA zone 9-11 and can tolerate temperatures down to 27°F (-3°C) for short periods. However, it thrives best in warmer climates with temperatures ranging from 65°F to 85°F (18°C to 29°C).
Uses
The African Milk Tree is widely used as an ornamental plant, both indoors and outdoors.
Wildlife Attraction
Euphorbia trigona may attract insects and small birds in its natural habitat, although it is not particularly known for supporting a wide range of wildlife.
Toxicity
One important aspect of the African Milk Tree is its toxicity. Like other Euphorbia species, this plant produces a milky white sap when its stems or leaves are damaged. This sap is toxic and can cause skin irritation, rashes, or blistering if it comes into contact with the skin. It is also harmful if ingested, making the plant toxic to humans and pets.
Read also: Learn About African Milk Trees
Invasive Potential
The African Milk Tree can potentially become invasive in certain regions. It has become naturalized in places like Cuba and India, where it grows in disturbed sites and abandoned gardens, forming dense thickets in dry and semiarid areas. The plant spreads primarily through vegetative reproduction, with cuttings and stem fragments easily taking root and establishing new plants.
African Milk Tree Propagation - How to get your cutting and root it in soil successfully
Benefits of Growing
The primary benefits of growing Euphorbia trigona include its architectural beauty, drought tolerance, and ability to thrive with minimal care.
General Care Tips
Light
The African Milk Tree thrives in bright, indirect sunlight, but it can also tolerate direct sunlight in the morning or late afternoon. 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.
Soil
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. 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. A good soil will have lots of perlite or vermiculite for drainage and some organic matter for nutrition.
Watering
The African Milk Tree is highly drought-tolerant, but proper watering is essential to keep it healthy. Water thoroughly, but make sure the soil dries out completely between waterings. Tip: It’s better to underwater than overwater this succulent. 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. If the soil is allowed to stay too wet, it can kill the plant. 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. African Milk Tree thrives in dry soil and should be watered sparingly.
Read also: Comprehensive Propagation Guide
Temperature and Humidity
The African Milk Tree prefers warm temperatures and can thrive in conditions ranging from 65°F to 85°F (18°C to 29°C). While it can tolerate brief drops in temperature, it is not frost-hardy and should be protected from temperatures below 40°F (4°C). 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. African milk trees are happy with the temperature conditions achievable in households. Daytime temperatures of 65 to 90° F. and nighttime temperatures ranging from 60 to 75° F. 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.
Fertilizing
African Milk Trees benefit from occasional feeding during the growing season, but they don’t require much fertilizer. 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. Minimal nutritional intervention is required. It is important to differentiate the non-active growth period of your Euphorbia and to give it a rest.
Pruning
Focus on pruning evenly on both sides of the plant to avoid creating an imbalanced load that could cause the plant to lean or pull out of the soil. If your African Milk Tree becomes too tall, you can prune it. Use a sharp, sterilized knife to cut the top of the plant, ensuring an even cut. Pruning can work well to keep the size of the plant in check and to create a more balanced branching structure. You should trim carefully to protect yourself and the plant, and with the expectation that the plant will have a different appearance afterwards. When you make a cut to the stem, the stem will not regrow from that point or grow in precisely the same direction. As long as the plant is healthy, it should send out one or more shoots from a point below the cut in any direction.
Make sure that your plant is in a healthy condition and getting the best care before you cut for best results. Spring is the best time to prune but early summer is fine for a vigorous plant. Pruning at the right time of year gives the Euphorbia the best chance to recover from the stress easily. Be careful not to remove too many branches at one time because that could shock the plant. As a general rule, no more than 1/3 of the plant should be removed during pruning. Pruning a branch at its point of origin will look the tidiest but that may not be possible for tall plants with fewer main stems.
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. Determine the shape and height you would like for your plant. After each cut, spray the wound on the remaining plant with water.
Overwintering
To overwinter the African Milk Tree, move it indoors before temperatures drop below 40°F (4°C), as it is not frost-tolerant. Reduce watering significantly, allowing the soil to dry out completely between waterings. Avoid fertilizing during winter, as the plant enters a dormant period.
Propagation
Propagating an African Milk Tree is a straightforward process, primarily done through stem cuttings.
- Choose a Healthy Stem: Select a healthy, strong stem from the plant.
- Wear Protective Gear: Since the plant produces a toxic sap that can irritate the skin, always wear glove and eye protection when handling it.
- Cut the Stem: Use a sharp, sterilized knife or scissors to cut a 4-6 inch section of the stem. African milk tree should not be rooted in water or it will rot. To propagate this plant, you can take a 5-inch stem cutting in late spring or early summer. 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.
- Let the Cutting Callous: Place the cutting in a dry, shaded location for several days, allowing the cut end to callous over. 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 the Soil: Use a well-draining cactus or succulent mix.
- Plant the Cutting: Once the cutting has calloused, plant it in a small pot filled with the prepared soil. 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.
- Water Sparingly: After planting, water lightly. Allow the soil to dry out between waterings to avoid root rot.
- Provide Light: Place the newly planted cutting in a location with bright, indirect light.
- Wait for Root Growth: It may take several weeks for the cutting to develop roots.
Potting and Repotting
Potting and repotting an African Milk Tree is essential for maintaining its health and ensuring proper growth.
- Choose the Right Pot: Select a sturdy pot with drainage holes. The plant’s height and weight can cause it to tip over, so a heavy, wide-bottomed pot (like a terracotta pot) can help provide better stability. 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.
- Soil: Use a well-draining cactus or succulent soil mix. You can also make your own by combining potting soil with sand or perlite for improved drainage.
- Potting Process: Fill the pot with the cactus mix, leaving enough room to plant the African Milk Tree.
- Watering After Potting: After potting, water lightly to settle the soil, but ensure the soil dries out before the next watering.
- When to Repot: Repot every 2-3 years or when you notice the plant becoming root-bound or outgrowing its pot. While it is young and growing most rapidly, move your plant up one pot size each spring.
- Prepare a Larger Pot: Choose a pot that is 1-2 inches larger in diameter than the current one.
- Remove the Plant: Wear gloves to protect yourself from the plant’s sharp spines and toxic sap. Gently remove the plant from its pot. 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.
- Examine the Roots: Inspect the roots for any signs of rot or damage.
- Repotting Process: Place the plant in the new pot and fill in around the roots with fresh, well-draining soil. Ensure the plant is centered and stable.
- Watering After Repotting: Water the plant sparingly after repotting.
Common Problems
- 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.
- Disease: The most common disease issue is root rot, caused by overwatering.
- 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. 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.
Dropping limbs indicates that the plant is under significant stress and often involves issues occurring at the roots of the plant. 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. 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.
Frequently Asked Questions
Is the African Milk Tree edible? No, the African Milk Tree is not edible.
What to do if my African Milk Tree becomes too tall? If your African Milk Tree becomes too tall, you can prune it. Use a sharp, sterilized knife to cut the top of the plant, ensuring an even cut. The cuttings can be propagated after they have calloused over.
Is the African Milk Tree toxic to dogs? No, the African Milk Tree is toxic to dogs. If ingested, it can cause vomiting, diarrhea, or other symptoms.
How often should I water the African Milk Tree? The African Milk Tree is drought-tolerant and can go for several weeks without water.
Can I put the African Milk Tree outside? Yes, you can put the African Milk Tree outside during warmer months if the temperature stays above 40°F (4°C).
What kind of light does the African Milk Tree need? The African Milk Tree prefers bright, indirect light, though it can tolerate some direct sunlight, especially in the morning or late afternoon.
What are the most common pests for the African Milk Tree? The most common pests are mealybugs, scale insects, and spider mites.
While every effort has been made to describe these plants accurately, please keep in mind that height, bloom time, and color may differ in various climates. The description of these plants has been written based on numerous outside resources.
