Talk to any European, especially an Italian, and they will rave about the beauty of "mimosa" in cut-flower bouquets. Blooming in late winter and early spring, this Australian tree, also commonly called silver wattle, produces puffy clusters of fragrant yellow flowers. The mimosa acacia (Acacia dealbata) grows outdoors in warm, temperate Mediterranean-like climates such as U.S. Department of Agriculture hardiness zones 9 through 11.
Usually found in the open areas of woodlands, in forest ravines or on the edges of swamps, mimosa acacia is native to New South Wales, Victoria and eastern Tasmania in extreme southeastern Australia. It is naturalised, growing so well you'd think it was a native tree, in both the southwestern part of Western Australia, around Perth, and the southeastern part of South Australia, near Adelaide.
Mimosa acacia grows with an open-branched habit to between 50 and 100 feet at maturity. Its evergreen folaige is hairy and slightly bluish green in colour, looking like feathers. Each leaf comprises many smaller stems that each carry 40 to 80 tiny leaflets. At the ends of branches, in late winter to early spring, it displays large showy clusters of many small, rounded flowers, followed by small, waxy seed pods that ripen to beige with reddish and purplish hues.
Both the foliage and flowers highlight the most ornamental features of the mimosa acacia, although the smooth grey bark is also attractive, becoming deeply corrugated on very old trees. The fernlike leaves and tufted yellow cotton-candy-like flowers make a striking statement in the garden and add a sweet but not overpowering fragrance. The many small seed pods add texture in summer, contrasting well with the foliage.
Grow mimosa acacia in a moderately fertile soil that drains well. The soil needs to be acidic or neutral in pH. Full sun--more than 8 hours of sunlight daily--creates the best-shaped tree and maximum flowering. Locate it in a wind-protected spot for flower longevity and diminished risk of tattered leaves. Tip-prune to harvest flowers, but do not severely prune back branches. During the growing season water and fertilise freely, but allow soil to become much drier in winter, and also stop fertilising.
Mimosa acacia becomes a magnificent early spring-flowering tree for gardens in regions such as southern Spain, Italy and Greece as well as South Africa, Chile and southern California in the United States. It doubles as a shade tree in the summer months. The clusters of flowers can be cut from late winter to mid-spring for cut-flower bouquets. Mimosa is grown for the cut-flower industry worldwide, either outdoors in the appropriate climate for seasonal harvesting or in large sheltered greenhouses.
Over 1000 species of acacia exist worldwide, and if this particular species is not available, other ornately flowering types may substitute for Acacia dealbata in cut flower arrangements. Bailey's wattle (Acacia baileyana), also called Acacia floribunda, has leaflets that bear a faint purple-silver colour. The leaflets of Queensland silver wattle (Acacia podalyriifolia) emerge silvery white, contrasting beautifully with the yellow flowers. The elephant ear wattle (Acacia dunnii), which blooms in repeat flushes year round, may also be a substitute when other mimosa are not in season.