The mimosa acacia, also known as the golden mimosa, cootamundra wattle or, more commonly, Bailey's acacia, is a graceful, medium-sized tree or large shrub. It is named after the Australian botanist Frederick M. Bailey, the Queensland Royal Botanist and an avid plant collector from the late 1800s.
The acacia family is one of the largest tree families in nature, with over 800 species spread across Africa, Australia, the Pacific Islands and North and South America. Acacias are a varied group, from short, spiny bushes to tall, elegant trees. Some have heartwood so dense it sinks in water, and others provide gum arabic, an ingredient in consumables like candy, pharmaceuticals, cosmetics and beer. Many acacias, like the mimosa acacia, are useful ornamental trees, according to .
The mimosa acacia has evergreen, bipinnate leaves and smooth gray bark. The multiple long, narrow leaflets arranged on each side of the leaf stalk are blue-green or silver-green, and are larger than many other acacia leaves. The compound leaves look like large feathers, and cast a dappled shade. The tree is rounded and grows to 25 feet tall. Nurseries train Bailey's acacias into single-trunked trees or multi-trunked shrubs. Nurseries also sell a purple-leafed variety, 'Atropurpurea,' which makes a colorful accent plant.
The mimosa acacia prefers well-drained, rich soil but is not fussy. This tree takes advantage of many soils, from clay soils to fast-draining sands. Mildly acidic to strongly alkaline soils don't bother Bailey's acacia. It is also moderately salt tolerant. Beware of planting this tree near patios or underground utility lines, as the roots are fairly invasive. Bailey's acacia is a fast-growing tree, capable of growing over 3 feet a year. In exchange for the fast growth, however, the mimosa acacia has a relatively short lifespan of roughly 50 years.
The mimosa acacia is named for its flowers, which are large, fluffy clusters of yellow blossoms. The mimosa tree (Albizia julibrissin), which gives its name to the mimosa acacia, has feathery, pink blossoms, but the mimosa acacia's blooms are brighter, tightly clustered, and look like tiny sunbursts. This early-blooming acacia blooms in late winter or early spring and usually reaching a peak flowering period in January to February. After the bloom, the mimosa acacia produces seed pods that grow 1-1/2 to 3 inches long.
Mimosa acacias have invasive roots in home gardens, but the tenacious roots prevent erosion on hillsides and other unstable areas. Their relatively low height and generous foliage screens unwanted views. Dry landscapes do not deter the mimosa acacia, which is drought-tolerant.