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Black Wattle, also known as Acacia mearnsii, refers to a type of tree and shrub indigenous to Australia. The aboriginal tribes in Australia used the wattle's bark, flowers, and sap in many different ways. Foreigners brought the tree's seeds to different parts of Africa, where black wattle became a cash crop. Today, these regions are dealing with the overpopulation of Acacia mearnsii.
Acacia is a genus which belongs to the Fabaceae family of the plant kingdom. The genus covers more than 1,500 different species of trees and shrubs, approximately 1,000 of which are indigenous to the Australian continent. In the initial stages of growth, black wattle resembles a shrub, taking on the form of a tree at maturity. The trees range anywhere from 16.4 to 32.8 feet (5 to 10 meters) tall, some of them growing up to 164 feet (50 meters) tall.
The tree is covered with yellow flowers which are approximately 0.07 inches (1.8 mm) long. The black wattle's bark, which contains a high percentage of tannin, houses different types of insects. In Australia, the Tasmanian Hair Streak Butterfly lays eggs within the cracks of the bark.
The Aboriginal peoples and Australian colonists used all of the parts of the black wattle trees and shrubs. They extracted antiseptics from the tree's bark and used it to heal wounds and ease aches. People also split the bark to produce coarse strings for weaving baskets and mats. Colonists burnt the shrubs and used its ashes to create lye, which they mixed with animal fat and perfumed with oils to create soap. In addition to these products, the trees were used as firewood and chopped down to build structures for humans and animals.
The wattle's bark has a high tannin content, ranging from 25 to 45 percent. The tannic acid extracted from the bark was used to tan animal hides. Adhesives for plywood were also produced from the tree's tannin. In Australia, the logging of black wattle for building materials and other products led to a deforestation of the woodlands in the 1900s.
The species is also found in other areas of the world, including California, Hawaii, and parts of Africa. Historians speculate that a missionary brought black wattle, eucalyptus, and other seeds from Australia to Kenya in the 1880s. Eventually, other merchants and missionaries introduced the plants to natives in the early 20th century. The wattle became a cash crop in Kenya and other African countries, where it was used for firewood and building material.
Today, black wattle trees and shrubs present a problem for agriculturalists. The United States Department of Agriculture listed the plant as a noxious weed in the state of Hawaii, as it can be invasive against the local vegetation. Locals are attempting to eradicate black wattle and its seeds in South Africa, as the trees are competing against native plants by taking up a majority of the resources, including sunlight and water.