The mimosa (Acacia dealbata), also called the silver wattle, is native to Australia. An evergreen, the mimosa grows as a shrub or a tree. It reaches a height of 100 feet in its wild habitat but when grown as an ornamental landscape tree it rarely exceeds 30 feet. The tree lives only 30 to 40 years in the wild. Despite being an evergreen, in cold winter weather, the tree quickly takes on a yellowish cast but returns to its bluish-green shade with the arrival of spring.
In its native habitat, the mimosa tree flowers during the winter months. It produces large clumps of inflorescences that contain up to 42 bright yellow flowers. The tree is highly fragrant when in full bloom. When grown as an ornamental in the United States, the tree flowers in early spring. Following flowering, flat fruit pods appear, which are dispensed by the wind.
The mimosa tree grows best in U.S. Department of Agriculture zones 8 to 11. The tree will not tolerate temperatures that drop below 20 degrees F, and will suffer widespread foliage death. If the temperature dips to below 15 degrees F, the tree will quickly die. The mimosa can be saved and returned to its grandeur if a heavy frost simply blackens its leaves. Removal of the damaged areas will help the tree recover in the spring.
The mimosa flowers best in full sunlight. It requires well-draining soil that is slightly acidic. It will not tolerate wet roots for an extended time period. Once planted, the tree is moderately drought tolerant.
In the 19th century, the mimosa tree was introduced to the south of France where it quickly became a favorite garden tree and spread throughout Europe. It escaped cultivation within France and has managed to naturalize throughout the region with ease. In the United States, the tree has also managed to escape cultivation and is considered invasive.
The tree easily grows from seeds. Plant the seeds in February to June for best results. The tree normally invades and establishes itself after a wildfire in its native home of Australia. Wildfires also cause the tree to live a limited lifespan in the wild.