Senegalia burkei, commonly known as the Black Monkey Thorn or Scented Thorn, is a distinctive tree species native to Southern Africa. It belongs to the Fabaceae family, which is the pea or legume family, and was formerly classified under the genus Acacia. This thorny, deciduous tree is recognized for its presence in its natural habitat and its various applications.
Characteristics of Senegalia burkei
Senegalia burkei is a medium to large deciduous tree, typically growing 12 to 25 meters tall, sometimes up to 30 meters. It develops a spreading, rounded, or flattened crown, providing dense shade. The bark on younger branches is grayish-yellow to reddish-brown and velvety, transitioning to pale or dark grayish-yellow to dark brown on older stems, often becoming irregularly fissured and flaking.
The branches have dark, sharply hooked thorns, 3–9 mm long, growing in pairs. Its leaves are twice compound and alternate, dark green, with 3 to 10 pairs of feather-like structures.
Flowers are small, yellowish-white, and sessile, arranged in spikes 15–85 mm long. These scented blooms appear in late spring or summer, notable for their distinct pinkish to reddish calyx. Following flowering, the tree produces flat, bean-like pods that are initially reddish-brown and turn dark brown or black as they ripen. These pods mature from December to May.
Natural Habitat and Distribution
Senegalia burkei is indigenous to Southern Africa. Its natural geographical range includes southeastern Botswana, southeastern Zimbabwe, Mozambique, Eswatini, and South African provinces such as Gauteng, Limpopo, Mpumalanga, KwaZulu-Natal, and North West. This tree is a characteristic component of the bushveld, a sub-tropical woodland ecoregion.
The species typically inhabits dry river valleys, thornveld, and mixed woodlands. It prefers hot and dry deciduous woodland conditions, indicating its resilience to arid and semi-arid climates.
Cultivation and Care
Cultivating Senegalia burkei requires attention to its environmental preferences. The tree thrives in full sun conditions and adapts to a range of well-draining soil types, including sandy and loamy compositions. It is also frost-hardy, able to withstand cooler temperatures, though severe, prolonged freezes might cause stress.
Young trees require regular watering to establish their root systems. However, mature Senegalia burkei specimens exhibit strong drought tolerance, needing minimal irrigation once established. Overwatering should be avoided to prevent root issues.
Pruning focuses on shaping the tree and removing dead or damaged branches. Senegalia burkei responds well to pruning, which can help in developing a dense canopy. This species is generally not prone to significant pest infestations; maintaining good air circulation can help deter problems. Its root system can be extensive, so plant it at least 5 meters away from paving, foundations, or pools to prevent damage.
Propagation of Senegalia burkei
Senegalia burkei is primarily propagated from seeds, a method requiring specific pre-treatment to encourage germination. Fresh seeds should be collected directly from the tree, as ground-collected seeds may be insect-infested. These seeds have a hard outer coat that benefits from scarification.
A common method involves soaking seeds in hot water overnight to soften the seed coat. If seeds do not swell after the initial soak, the process can be repeated. Swollen seeds are then ready for sowing in a well-draining seedling medium, lightly covered to a depth of about 0.5-1 cm.
Germination usually occurs within 3 to 4 weeks under optimal conditions, including a warm environment (around 25°C or higher) and consistent moisture. Seedlings can be transplanted into individual nursery bags or pots once they reach the two-leaf stage. Germination rates are lower in autumn or winter; warmer temperatures in spring generally yield better results.
Ecological and Practical Significance
Senegalia burkei is ecologically significant in Southern African ecosystems. As a Fabaceae family member, it contributes to nitrogen fixation, enhancing soil fertility. The tree provides habitat and food for various wildlife. Its leaves and pods are a food source for animals such as black rhino, giraffe, kudu, nyala, impala, and elephants. The gum is consumed by monkeys and bushbabies, and its fissured bark attracts woodpeckers and red-billed wood hoopoes.
Beyond ecology, Senegalia burkei holds practical value. It is appreciated as an ornamental tree in landscaping, providing dense shade. Its wood is strong, hard, heavy, and termite-resistant, with a golden to dark brown heartwood. This makes it suitable for crafting furniture, tool handles, and durable fence posts. It also serves as good quality fuel.
Traditionally, its bark and roots are used for medicinal purposes, such as treating eye and back complaints. The roots can also yield a yellow dye. Its edible gum is also consumed. The tree is a popular choice for bonsai cultivation. It is currently assessed as being of Least Concern regarding its conservation status.