Over the years, Strawberry Hill Farm has benefitted from the utilisation of Acacia melanoxylon (Blackwood), which is a feracious invasive but is also a highly valued timber tree for the furniture industry. In this blog, we will look at how the species was introduced to South Africa and our farm. We discuss some of the interesting facts about the species that have helped it spread rapidly and gain a formidable reputation in the furniture industry.
Blackwood was introduced to the Cape Town region in 1848 and has been present in the forests of the southern Cape since 1856 (Geldenhuys, 1996). Since 1909, it has been extensively planted in the southern Cape forests to suppress weed growth on exploited sites (Geldenhuys, 1996). However, these plantings were discontinued around 1930, following the Phillips 1928 study, which claimed that the species depletes soil moisture, suppresses indigenous tree seedlings, and spreads rapidly.
Since being planted, the tree has spread over much of South Africa's forested areas, from the Cedarberg in the west to the Cape, KwaZulu Natal, and Mpumalanga (Goldblati, 1978). The species is found in the southern Cape, including indigenous forests, plantation areas, under mature pine stands, along roadsides and riverine areas, farmlands, and wastelands.
Over the last few decades, researchers have attempted to understand the rapid spread of this species, the studies concluded that the fast spread was due to the constant and prolific production of seed, with a high germination potential (90 -100 percent). Blackwood seeds have a unique, rounded reddish, fatty funicle that encourages extensive propagation of the seed by birds, such as the Knysna Lourie (Tauraco Corythaix) and the Rammeron pigeon (Columba Arquatrix). The seed may also lie dormant in the soil until a disturbance occurs, such as a fire, at which point it germinates quickly.
The presence of this species on our farm supports the research findings, as well as its rapid spread. In an interview with one of our longest-serving employees, Mr Danie Jacobs, he alluded to the fact that the blackwood on the farm was not introduced to the farm by planting, but rather through seeds dispersed from neighbouring farms. Because of its market value at the time of germination in the late 1800s, this species was given care. Treatments included everything from thinning to pruning. Over the years, this has helped the species to thrive on the farm and it has been harvested extensively as a valuable timber tree.
Interestingly, the bigger the tree crown the more likely the tree will suffer from windfall, meaning the roots of this species cannot grow enough to provide stability to the tree. We have observed significant windfall during the heavy berg winds that occur in the winter months.
After disturbance of the forest canopy and floor, regeneration occurs in copious amounts and quickly. It spreads quickly in wide gaps (Goldblati, 1978). Blackwood grows slowly at first, but after about 10 years, its diameter can actually increase if competition between trees is handled by thinning. Sawlog harvesting isn't anticipated for another 25 years. In areas with lower rainfall, it can take at least 50 years to reach the final harvest.
While we are removing this invasive tree and restoring indigenous forests, our farm places a high priority on this species as it is a valuable timber species. We have taken advantage of the species' beneficial properties, while keeping the spread under control. Blackwood timber is used for boat building, musical instruments, and craft pursuits, and we are one of the few farms to harvest blackwood and use it for furniture making on the farm.