African milk tree (Euphorbia trigona)

Overview

The striking Euphorbia trigona, commonly known as the African milk tree, is celebrated for its architectural, upright form derived from its fleshy, three-sided branches. This plant brings immediate vertical interest to xeriscape designs or sunny patios. Mature specimens in ideal climates can soar up to 12 feet tall, displaying a stout trunk that provides strong visual structure.

Native to the seasonally dry tropical forests of Central Africa, the African milk tree thrives in heat and dry conditions once established. It is widely used globally as a sculptural ornamental, often cultivated as a robust houseplant in cooler regions. Gardeners value the Euphorbia trigona for its low water demands and dramatic, branching silhouette.

This deciduous shrub sheds its small leaves seasonally, accentuating the geometric form of the stems, which are lined with small, sharp spines. Its common name is derived both from its origin and the milky white sap that flows from any cut, a characteristic shared by many euphorbs.

Fast Facts

• Plant Family: Euphorbiaceae
• Plant Type: Deciduous shrub
• Native Range: Central Africa
• Hardiness Zones: USDA Zones 10-10
• Size at Maturity:
  • Height: 6-12 ft
  • Spread: 5-10 ft
• Bloom Time: Seasonal bloomer
• Sun Exposure: Full sun to part shade
• Water Needs: Dry to medium
• Maintenance Level: Medium

How to Grow

Planting the Euphorbia trigona requires an emphasis on drainage, as its roots cannot tolerate excessive moisture. In frost-free USDA Zones 10-11, plant in a location receiving full sun, though partial shade is acceptable, especially in the hottest afternoon periods. The absolute requirement is sharply-drained soil; amend heavy soils heavily with grit or sand to prevent drowning the roots.

Care involves watering consistently during the active growing season of summer, ensuring the soil dries out completely between thorough soakings. Reduce watering significantly as temperatures cool during winter dormancy. This species is intolerant of frost, making it strictly suited for warmer climates outdoors or requiring overwintering indoors for potted specimens.

Potted African milk tree plants benefit from standard succulent care, meaning bright light and infrequent watering. When transplanting or pruning mature plants, exercise caution due to the irritating milky sap. Medium maintenance is required, mainly focused on ensuring ideal drainage and monitoring for common succulent pests.

Landscape Uses

When winter hardy, the Euphorbia trigona excels as a specimen plant, instantly drawing the eye with its towering, architectural lines. Its ability to form dense thickets means it functions admirably as an informal screen or hedge in arid landscaping schemes. For gardeners outside Zone 10, growing the African milk tree in large containers allows for easy relocation indoors before the first frost threatens.

In mixed succulent borders, pair the upright structure of Euphorbia trigona with contrasting textures, such as low-growing spreading aloes or mounding sempervivums. The linear form also provides excellent background structure against lower-growing mounding perennials that enjoy similar sun and dry conditions. Containers can feature the Euphorbia trigona as the dramatic thriller element, surrounded by spiller and filler succulents.

Standout Features

Flower Qualities

• Insignificant

Noteworthy Characteristics

Euphorbia trigona, commonly called African milk tree, is an upright, shrubby, branching succulent native to central Africa where it typically grows in seasonally dry tropical forests. It is widely cultivated in warm, tropical, subtropical, and arid regions an ornamental plant, and around the world as a houseplant. Mature plants can reach up 6-12’ tall with a stout, cylindrical, grey trunk and fleshy, 3-5 sided branches which are referenced in the specific epithet trigona meaning “three-angled.” The common name African milk tree reflects its native range and the milky white sap exuded when stems are cut.

Tolerances

• Shallow-Rocky Soil

Potential Problems

The primary cultivation issue for Euphorbia trigona is root rot, which inevitably occurs if soils remain overly moist, especially during cooler months. Prevention involves strict watering discipline, allowing soils to fully dry between irrigation events. Pests like aphids, mealybugs, and spider mites can attack the stems, requiring inspection and treatment with horticultural oil or insecticidal soap. Handle this plant carefully, as contact with the milky sap can cause skin and eye irritation.

Frequently Asked Questions

What hardiness zones is African milk tree suitable for?

The African milk tree is winter hardy only in USDA Zones 10 through 10 outdoors. In cooler locations, it must be grown in containers and overwintered indoors.

How large does Euphorbia trigona grow?

Mature Euphorbia trigona typically reaches a height between 6 and 12 feet, with a spread of 5 to 10 feet when grown in optimal outdoor conditions.

What sun exposure does Euphorbia trigona need?

This succulent performs best when given full sun exposure, though it can tolerate, and sometimes benefit from, part shade, particularly during the most intense parts of the afternoon.

When does Euphorbia trigona bloom?

This plant is described as a seasonal bloomer, though the small, inconspicuous flowers produced by mature specimens are rarely considered horticulturally significant.

Conclusion

The African milk tree offers exceptional architectural value and drought tolerance, making the Euphorbia trigona a standout choice for low-maintenance, high-impact tropical or arid garden designs. Its needs are simple: maximum drainage and protection from frost. Assess your local USDA zone compatibility before incorporating this bold succulent into your landscape plans.

Companion Planting

Choosing appropriate companions is crucial for the long-term health of the African milk tree, as its drainage requirements are absolute. Select other succulents or desert-adapted perennials that share the need for sharp drainage and infrequent watering, such as various species of Agave, Yucca, or Senecio. Avoid planting near thirsty turfgrass or moisture-loving annuals, as conflicting water schedules will likely lead to root rot in your Euphorbia trigona.

For aesthetic contrast, group the tall, columnar habit of the African milk tree with plants offering softer textures or low, spreading habits. Trailing stonecrops or low-growing Dudleya species create an excellent visual anchor at the base, highlighting the vertical thrust of this euphorb.

Propagation Tips

The most straightforward method for increasing your stock of Euphorbia trigona is through stem cuttings, as the plant readily roots from vegetative fragments. Take cuttings during the warmer months when the plant is actively growing or preparing to do so. Ensure the cut surface is allowed to dry and form a callus completely—this can take several days to a week—before planting the cutting into a sterile, gritty rooting medium.

Once calloused, gently seat the cutting an inch or two deep into the mix. Do not water immediately; wait about a week after planting before the first light watering. Providing warmth and bright, indirect light will encourage root development for your new African milk tree specimen.