Mimosa (Acacia dealbata)

Arabic name: أكاسيا

There are about 700 to 800 species of Acacia, mostly from tropical regions, but the most commonly grown species are native to Australia.  This tree has naturalized in many areas, and is very common and popular in the Mediterranean region.  The Mimosa (Acacia dealbata) is a winter flowering species, with silvery leaves and abundant masses of fragrant yellow flowers covering its branches in January and February.

This attractive evergreen tree can grow to a height of 6m, with a spread of 5m, and has a very fast growth rate of 25 - 50cm or more per year, but a relatively short lifespan of 20 – 30 years.

Requirements:
Mimosas grow in full sun and are drought tolerant.  They require well-drained, slightly acidic soil, and need to be sheltered from strong winds.

Water usage:
Mimosas require no watering once established.  Generally, trees need supplemental irrigation to get established, especially if planted after the rainy season.  During the first year, irrigate in the amount of 20 – 25 liters of water twice a week. During its second year, a tree needs to be irrigated in the amount of 40 liters once a week.  Beginning with the third year, trees usually get established, and some, like the Mimosa, do not require any supplemental irrigation. 

Appearance:
The mimosa grows into a middle-sized tree, with a rounded shape, and is very showy.  Its bark is smooth, and silvery gray.  Its attractive feathery leaves are finely divided, and grow to 3cm long, with numerous small leaflets.  The leaflets, which are about 0.7cm long, are bluish green and smooth on both sides.  Its showy and fragrant yellow flowers, which bloom in late winter to early spring, are borne in dense, fluffy clusters of golden yellow balls that are 0.6cm in diameter.  Fruits are flat, brown-colored pods.  They are about 9cm in length and contain the plant’s seeds.

Notes on use:
Distinguished by its impressive yellow flowers; good along roads and for erosion control on hillsides.

Propagation:
Mimosas can be propagated by seeds and semi-hardwood cuttings in the summer.  To propagate by seed, remove the seeds from the dry pods and place in boiling water.  Once cool, swollen seeds may be sown.

Maintenance: 
Requires little maintenance.  May be pruned after flowering to encourage compact growth, but take care to avoid hard pruning.

Care should be taken when transplanting young Mimosas.  Also, make sure to stake well.

Comments:
The Mimosa is attractive to wildlife, and also is commonly grown by the cut-flower industry both for its foliage and flowers. It also is known for its Nitrogen fixing abilities that benefit other plants growing nearby as well as the tree itself.

This article is part of a series of articles prepared by the Center for the Study of the Built Environment (CSBE) on water conserving landscapes. 

For additional information on water conserving gardens, visit the CSBE web site at www.csbe.org

Support for the CSBE project on water conserving landscapes is provided by WEPIA (Water Efficiency and Public Information for Action), a program being implemented in collaboration with the Ministry of Water and Irrigation and funded by the United States Agency for International Development (USAID).