The African Sumac, scientifically known as Rhus lancea (or Searsia lancea), is a popular evergreen tree native to Southern Africa’s arid regions. This species is highly valued in landscaping for its dark green, willow-like foliage and its ability to thrive in harsh conditions. Its resilience, fast growth rate, and dense canopy make it a favored choice for providing shade and visual appeal in dry climates. While generally low-maintenance, the African Sumac is susceptible to specific biotic and abiotic issues that require proactive management.
Managing Common Pests and Pathogens
African Sumac is generally robust, but it can become a target for certain insect pests, particularly when the tree is stressed. Aphids are common, congregating on new growth and excreting honeydew. This honeydew becomes a substrate for sooty black mold, which coats the leaves and impairs photosynthesis.
Scale insects also pose a threat, appearing as small, stationary bumps on stems and leaves where they feed on plant sap, leading to yellowing foliage and stunted growth. For light infestations, a strong jet of water can physically dislodge the pests. Persistent populations can be treated with horticultural oils or insecticidal soaps, which smother the insects without leaving harmful chemical residues.
The tree is also susceptible to fungal root diseases, most notably root rot and Texas root rot, which are often fatal. These fungi thrive in overly saturated, poorly drained soil conditions. Visible symptoms include sudden wilting, chlorosis, and rapid leaf drop, which quickly leads to tree death. Since there are no effective chemical treatments once these diseases are established, prevention through proper watering and soil management is crucial.
Addressing Environmental and Cultural Stress
Improper maintenance practices are the most frequent cause of health decline in African Sumac. Because of its drought-tolerant nature, the most common error is overwatering, which starves the roots of oxygen and creates the anaerobic environment necessary for root rot. The tree requires deep, infrequent irrigation, allowing the soil to dry out significantly—at least 4 to 6 inches below the surface—between watering cycles. Conversely, severe underwatering is indicated by wilting, shriveling leaves, and premature leaf drop, signaling the need for a thorough, deep soaking.
The tree requires well-draining soil, thriving in sandy or loamy compositions. Heavy clay soils should be amended to improve permeability and prevent water from pooling around the root crown. Nutrient deficiencies can also manifest, typically as chlorosis, where leaves turn yellow while the veins remain green, often indicating a lack of iron or other micronutrients. Applying a balanced, slow-release fertilizer in the spring can help maintain adequate nutrient levels, especially in alkaline or nutrient-poor soils.
While the African Sumac can tolerate brief dips below freezing, sustained cold temperatures, especially around 15°F, can cause damage in marginal planting zones. Young or newly planted trees may benefit from temporary protection, such as wrapping the trunk or covering the canopy during hard freezes.
Structural Issues and Pruning Needs
The natural growth habit of the African Sumac often leads to structural problems that must be addressed through careful pruning. The weeping nature of the branches, combined with rapid growth, can result in weak attachment points where branches meet the trunk or other limbs. These junctions are prone to splitting or breaking, especially under heavy foliage or strong winds.
To mitigate this hazard, structural pruning should be performed during the tree’s dormant season in late winter or early spring. This involves selectively thinning the canopy to reduce end-weight on long limbs and establishing a dominant central trunk. Arborists often use “drop-crotching” to reduce the tree’s overall height and spread by cutting large branches back to a healthy lateral branch.
Another characteristic issue is the aggressive production of suckers, which sprout from the roots or the base of the trunk. These suckers should be removed immediately and cleanly at their point of origin to prevent them from diverting energy from the main canopy. Consistent sucker removal is necessary to maintain the tree’s intended single- or multi-trunk form. Thinning the dense canopy also increases light penetration and air circulation, which helps minimize conditions that favor fungal disease development.