Acacia galpinii is a fast-growing, medium to large tree reaching to 100 feet or more in height, with a symmetrical, rounded canopy (1, 2, 3, 4, 5, 6). It is one of the largest of the acacias (3, 4, 7, 8). The trunk may reach more than six feet in diameter and is covered with rough, yellowish-brown bark that frequently exhibits longitudinal fissuring and persistent thorns (1, 2, 3, 4). The heartwood is dark, often reddish-brown, while sapwood is creamy in color (1, 2). Its wood is hard, dense and coarse grained (1). The tree’s root system is aggressive and may damage buildings and pavement (1, 5, 9). Pairs of dark, recurved thorns, measuring up to ½” long, are arranged oppositely below the nodes on branches (1, 3, 4, 7), and lenticels may be visible on younger branches (1). Leaves are alternate and bipinnate with 6-14 pairs of pinnae, each with 13-40 pairs of leaflets (1, 2, 3). The tree provides dappled shade in the summer, allowing grasses to grow below, and is deciduous in winter (1, 2, 5). Its fragrant flowers, appearing on axillary spikes measuring up to 4 ½” in length, are bisexual and light-yellow to creamy in color with a reddish calyx (2, 3, 6). Flowers give way to brown or reddish pods that can be nearly a foot long (2, 6). Pods, which take about six months to ripen, can dehisce on both sides, releasing the flat, oval seeds (1, 2, 3).

Acacia galpinii is native to southern and eastern Africa and is typically found in areas of open woodland and thornscrub as well as along riverbanks or in association with termite mounds (1, 2, 3, 4, 5). It is drought tolerant yet thrives in areas of summer rain (1, 2, 9). In its native environment, it grows between elevations of 1100 and 5000 feet (1, 3, 4, 6). It acts as a pioneer species and may be used in afforestation projects (2, 3). It is sometimes used as an indicator plant of well-watered, healthy grasslands (5, 9). As is common with other legume species, the tree readily forms symbiotic root nodules with Rhizobium and Bradyrhizobium bacteria (1, 2, 9). Monkeys often use the species as a refuge and food source, hence its common English name, and other animals, including elephants and giraffes, feed on the tree (1, 3, 5). The tree is fairly long lived (2). The tree’s genus name derives from the Greek word for “thorn” and the specific epithet was named after E.E. Galpin, a naturalist and plant collector from South Africa (2, 5, 9).