Common Problems With African Milk Tree

The African Milk Tree, or Euphorbia trigona, is a popular houseplant appreciated for its unique, candelabra-like structure and general resilience. Its vertical, three-sided stems give it an architectural quality that adds a dramatic touch to indoor spaces. While it is known for being relatively low-maintenance, it is not immune to issues that can cause owners concern. Understanding the signs of distress is the first step toward keeping this striking plant healthy.

Addressing Stem and Root Rot

The most serious threat to an African Milk Tree is root and stem rot, a condition caused by overwatering. This problem is made worse by using dense potting soil or a container that lacks adequate drainage holes. These factors create an environment where water stagnates, depriving roots of oxygen and inviting fungal pathogens to proliferate.

An affected plant will develop a soft, mushy base near the soil line, which may appear brown or black. This discoloration can travel up the stem as the decay advances. In some instances, a foul odor may emanate from the soil, signaling advanced decomposition of the root system.

To treat rot, remove the plant from its pot to inspect the roots. Healthy roots are firm and yellowish, while rotted roots will be brown, soft, and mushy. Using a clean, sharp knife, excise all compromised tissue from both the roots and stem, cutting back until only firm, green tissue remains. The healthy part of the stem must then be set aside in a dry, airy location for several days to a week to allow the cut surface to form a callus.

Once the cut has callused over, the salvaged portion can be repotted. Use a fresh, dry potting medium specifically formulated for cacti and succulents to provide sharp drainage. Do not water the newly potted cutting for at least a week to allow it to acclimate.

Solving Leaf Discoloration and Drop

Yellowing leaves can indicate a range of environmental stressors. If accompanied by a shriveled or thinning appearance of the main stems, yellowing points toward underwatering. Conversely, it can also be a natural process where the lowest leaves on the plant gradually die off as the plant matures.

Leaves that become brown and crispy are a symptom of severe thirst or sunburn. A plant suffering from a lack of water will show widespread crisping, while sunburn appears as scorched, brown patches on the side exposed to intense, direct light. The African Milk Tree prefers bright, indirect sunlight to prevent damage to its leaves and stems.

A sudden and widespread drop of leaves is a reaction to environmental shock. Moving the plant to a new location, a sudden temperature fluctuation from a draft, or a significant shift in light exposure can all trigger it to shed its leaves.

For yellowing or browning from water issues, adjust your watering schedule, allowing the soil to dry out completely between waterings. If sunburn is the cause, relocate the plant to a spot with bright but indirect light. To prevent leaf drop from shock, provide a stable environment, protecting the plant from drafts and avoiding frequent relocations.

Managing Common Pest Infestations

The most frequent culprits are mealybugs and spider mites. Mealybugs appear as small, white, cotton-like masses, often nestled in the joints where branches meet the main stem or along the plant’s ribs. They feed on the plant’s juices, and a large infestation can weaken it over time.

Spider mites are harder to see with the naked eye, but their presence is revealed by the fine webbing they spin between the plant’s stems and thorns. An infestation can cause the leaves and stems to look stippled or faded. These pests thrive in dry conditions, which are often the same conditions recommended for the plant.

For a minor mealybug issue, dip a cotton swab in rubbing alcohol and touch it directly to each pest to remove it. For more widespread infestations of either mealybugs or spider mites, spraying the entire plant with an insecticidal soap or a neem oil solution is effective. Since spider mites prefer low humidity, periodically misting the plant may help deter them.

Correcting Growth Issues and Damage

When the plant does not receive enough light, it can begin to stretch, a process known as etiolation. This results in a tall, spindly appearance with large gaps between the sets of leaves and thorns. To fix this, move the plant to a brighter location. While the stretched portion of the stem will not revert to its normal shape, new growth at the top will be more compact and healthy.

When a piece of the plant breaks, it will exude a milky white sap. This latex is a skin and eye irritant, so it is important to wear gloves when handling a damaged plant. The broken piece offers an opportunity for propagation. Set the broken branch aside for several days to allow the cut end to callus, then plant it in a pot with a well-draining soil mix.