How to Grow and Care for African Milk Tree

African milk tree (Euphorbia trigona) is native to Central Africa. It is often grown as a hedge due to its rapid and enthusiastic growth. This plant looks a lot like a cactus—hence its nicknames: candelabra cactus, cathedral cactus, friendship cactus, and good luck cactus—but it is actually a succulent plant. It features triangular stems, with three distinct sides seamed with ridges. The ridges are peppered with thorns and tear dropped-shaped leaves. This plant stays lush and green throughout its growing season, with new growth sprouting a light green hue. The Rubra or Royal Red cultivar is popular for its dramatic color, taking on bright red accents late in the season.

Like a cactus, African milk tree lives a long life and grows vigorously—approximately 1 to 2 feet a year up to 9 feet tall. But when grown indoors, this plant will only grow to about half of its maximum height. Only North American gardeners in states with arid climates—where the temperatures at night stay above 50 F (parts of Texas, California, Florida, and Arizona)—can grow African milk tree outdoors. For these lucky few, the plant provides a dramatic landscape addition not often seen in gardens throughout the United States.

The sap of the African milk tree is toxic to both pets and humans and can be irritating to the skin, eyes, and mouth. So much so that it can cause blisters, severe eye irritation, and, if swallowed, can sometimes result in convulsions.

African Milk Tree Care

African milk tree is popular as a decorative landscape feature, or a container plant, throughout South America and in the Mediterranean regions of Europe. Its dramatic size makes it a coveted plant by gardening enthusiasts, even though the plant may require training through pruning and staking to achieve the desired look. African milk tree has a small root system compared to its towering succulent body, so it can topple over easily when not properly pruned. Similar to a cactus, this succulent is fairly easy to propagate by simply breaking off one of the "arms" and rooting it in a potting medium. (Always do so with gloved hands.) This plant is also drought-tolerant and useful in climates requiring xeriscaping techniques, growing hardy in Zones 9b through 11. It can only survive to Zone 8 with winter protection.

Light

African milk tree likes bright, indirect sunlight. A southern-facing window works well for indoor growing, as does an outdoor spot that receives partial sun. An area that receives full sun is suitable, as long as the summers are not consistently hot. In this instance, extra watering may be needed to offset the hot, bright sunlight.

Soil

This succulent isn't fussy about its soil. Still, good drainage conditions are essential. Amend heavy clay soil for proper drainage and pH (African milk tree grows best with a soil pH of 6.1 to 7.8), or it may hamper the plant's growth. Sandy and sandy loam soils help this plant thrive in a xeriscaped environment.

Water

African milk tree doesn't need much water. Consider supplemental watering only if you're experiencing bad drought conditions. Otherwise, your region's normal rainfall should be sufficient. Indoor plants should be watered moderately once a week, but make sure to let the soil dry out between each watering to mimic its natural habitat.

Temperature and Humidity

This drought-tolerant plant enjoys a dry or arid climate and can withstand fairly hot temperatures. If your growing environment experiences hot summers, locate the plant in a spot with indirect sunlight or partial shade to avoid overheating. This plant doesn't need extra humidity, and growing it in a humid climate may cause stress, leading to fungus or pest infestation.

Fertilizer

In the spring and summer (during the plant's growing season), treat your African milk tree to a monthly feeding of half-strength diluted water-soluble fertilizer. Do not feed your plant during the off-season. Instead, allow it naturally to go dormant.

Pruning

African milk tree grows very tall and has a comparatively small and shallow root system. For this reason, older plants may become top-heavy, or even topple over, making pruning a necessity. When pruning, always wear gloves and use a sharp and sterilized knife to remove stems. The cut you create will dry over and make a callus on its own. Take care to keep the plant balanced on both sides to avoid a lopsided load on one side that may pull the plant out of the ground.

Propagating African Milk Tree

African milk tree propagates easily from cuttings. Due to the plant's toxicity, use proper protective gear when propagating—like heavy gloves—and wash your hands immediately if you get the milky sap on your skin.

Here's how to propagate African milk tree from cuttings:

1. Gather a sharp knife or hand pruners, alcohol wipes, a 4-inch container with potting medium, and coarse gravel.
2. Sterilize the blades of your knife or scissors with alcohol, and then cut off one of the plant's "arms" at its base.
3. Rinse the arm with cold running water until it stops oozing.
4. Let the arm sit in a dry spot on a paper towel, out of direct sunlight, for five to seven days, allowing the cut tip to callus over. (Note: Many growers bypass the callus stage and put the cutting directly into the soil. Root growth should occur within three weeks using this method, but it also makes the plant susceptible to root rot.)
5. Once the callus has formed, plant the arm in your container so that the end sits about an inch below the soil.
6. Add a layer of gravel on top of the soil to help keep the cutting upright.
7. Place the pot in a warm area with sufficient light and a temperature between 65 and 75 F, but out of direct sunlight. The cutting should root within two months.
8. As soon as you see root growth, transplant the plant into a slightly larger, 6-inch pot.

How to Grow African Milk Tree From Seed

You can grow an African milk tree from seed, though it's typically not recommended. Seeds can be difficult to find and even more difficult and slow to germinate. Instead, propagate the plant using the cutting method above.

Potting and Repotting African Milk Tree

Providing ample drainage and not overwatering are important considerations when potting African milk tree. This succulent will do best in a porous clay pot that absorbs excess water. Avoid glazed pots that add to the risk of overwatering. Sandy soil or potting mix formulated specifically for succulents allows for the best water drainage, especially when pumice or perlite is mixed in.

Repot the plant every year or two as it continues to grow taller. This will ensure that there's enough room for the roots to hold it in place (with a little help from stakes). Always wear gloves and note that it may take two people to repot a large plant, assuring a damage-free process.

Overwintering

African milk trees won't survive the cold. They typically won't flourish in temperatures below 50 F, so it's important to plant them in the ground only if your climate allows. Potted plants need to be brought indoors when temperatures drop. Place your succulent in a room with good air circulation to cut down the humidity and set it in a brightly lit window with indirect sunlight.

Common Pests & Diseases

A healthy African milk tree is usually not susceptible to pests or diseases. However, watch for the cotton-like threads made by mealybugs. To remove them, mix a solution of water and a few drops of mild dish detergent, then wipe the bugs off with a cloth dipped in this solution. You can also use a paper towel and rubbing alcohol to remove bugs, or spray off the bugs with water from a garden hose.

Overwatering your plant can cause fungal problems, such as cork disease, where the stems develop cork-like patches. Try saving the plant by cutting off the infected stems. Yellowing or browning of the succulent may also indicate root rot from overwatering. In this case, you will likely need to dispose of your plant entirely.

Common Problems

One of the most common problems with African milk tree is yellowing leaves. Even with the slightest bit of improper care, the leaves on your plant can change shade and fall off. The culprit is usually overwatering, underwatering, or cold temperatures. Preventing this issue is much easier than remedying it, so make sure your plant is located in a warm area, and water it just enough so that the soil dries out in between waterings, but is not consistently dry.