African milk tree care guide

The African milk tree looks like a cactus, but it is not one. It is a succulent euphorbia with tall, three-sided stems lined with short spines and small leaves. It grows fast in a sunny window and can reach the ceiling. Its milky sap is toxic, so handle it with care.

Light

Give it the brightest spot you have. A south or west window is best. It handles a few hours of direct sun.

In low light, the stems grow thin and lean toward the window. Turn the pot a quarter turn every few weeks to keep it straight.

If it lived indoors all winter, move it into stronger sun over a week or two. Sudden full sun can scorch the stems.

Water

Water when the soil is fully dry. Water until it drains, then empty the saucer. In spring and summer, that is about every two weeks. In winter, water once a month or less.

Too much water rots the stems from the base. When in doubt, wait. Read how to tell if a houseplant is overwatered or underwatered.

Soil and potting

Use a cactus and succulent mix. A clay pot helps the soil dry out.

Tall plants get top-heavy. Use a heavy pot that is wide at the base. Repot every two to three years in spring. Wear thick gloves and hold the stems with a towel. See how to repot a houseplant step by step.

Humidity and temperature

Dry indoor air is fine. Keep it between 16 and 29°C (60 and 85°F), and above 10°C (50°F). Keep it away from cold windows in winter.

Feeding

Feed two or three times in spring and summer with a cactus fertilizer at half strength. Skip feeding in fall and winter.

Pruning

Cut back stems that grow too tall or lean. Cut at a joint or where a branch meets the main stem.

Wear gloves and eye protection. The white sap irritates skin and can cause serious eye damage. Spray the cut with cold water to stop the sap. Wash your hands and tools after.

Staking

A tall African milk tree can tip over. Tie the main stem to a sturdy stake with a soft, loose tie. Give it more light so new growth comes in thick and strong.

Propagation

Cut a branch where it meets the main stem. Rinse the cut end under cold water to stop the sap. Let it dry for a week until the end forms a callus. Then set it in dry cactus mix. Give it a small drink after two weeks. Roots take four to eight weeks.

Problems

What you see	Most likely cause
Leaves fall off	Normal in winter, or a change in light or water
Soft, brown stem base	Rot from too much water
Thin, leaning stems	Not enough light
Hard, tan bark near the base	Normal aging, called corking
White or tan patches on the sunny side	Sunburn
White, cottony spots	Mealybugs

Pests

Mealybugs are the most common pest. They hide along the ridges and in the spines. Dab them with rubbing alcohol on a cotton swab. Watch for spider mites and scale too.

Pet safety

African milk tree is toxic to cats and dogs. NC State Extension rates its sap as a medium poison risk for pets and children. The sap burns the mouth, stomach, skin, and eyes. Keep it out of reach of pets and kids.

Varieties

• Green African milk tree has green stems and green leaves.
• Euphorbia trigona ‘Rubra’, also sold as ‘Royal Red’, has red leaves and red-tinged stems. The red is deepest in strong light.