Mimosa trees (Albizia julibrissin) are fast-growing, medium-sized deciduous trees desirable for their graceful foliage and delicate, silky pink flowers. In late summer, the tree produces long, unattractive brown seed pods that sometimes cling to the tree throughout the winter months. Mimosa trees are hardy and require only basic culture. They can spread quite rapidly, crowding out other plants. For this reason, they are considered undesirable trees in some areas, according to Tom Remaley, a horticulturist with the Plant Conservation Alliance.
Albizia julibrissin was first brought to the United States in 1745 from Asia. It is native to Southeast Asia, from India to Japan. This warm-climate tree can only thrive outdoors in USDA hardiness growing zones 6 through 9, according to Erv Evans, a consumer horticulturist with North Dakota State University. These areas of the United States have mild summers and winters, without extremely hot or cold temperatures.
Mimosa trees are extremely adaptable, which contributes to their ability to spread quickly. They can grow on almost any type of soil, including clay, loamy or sandy soil. When given a preference, Mimosa trees prefer rich, well-draining, loamy soil. These small trees are often planted in containers and used as patio trees. If planting your mimosa in a container, use a potting medium that contains a large amount of peat moss to aid in drainage.
Provide plenty of sunlight for your mimosa tree. While they can grow in partial shade, they prefer full sun and will bloom more prolifically when they get at least eight hours of sun per day, and preferably 12 hours of sun. These trees can be placed under an arbor or deciduous tree that lets in dappled light, but should not be grown under a thick, heavy tree canopy or in full shade.
Newly planted silk trees should be watered enough so that the soil remains slightly moist throughout the first growing season, especially if they are planted in containers, which dry out more quickly than trees planted in the ground. Do not over-saturate the soil, which can lead to root rot. Established trees need little to no hand watering, depending on the climate, and can survive periods of drought.
Problems and Diseases
Mimosa trees have brittle wood and are short-lived trees. They can be damaged or killed by vascular wilt and can suffer from fungal diseases that cause unattractive leaf spots or cankers to form. If planting a mimosa in a container, make sure the container and the soil are both sterile to reduce the chances of wilt developing. "Tyrone" and "Charlotte" are two cultivars resistant to diseases, according to Evans. Spray your tree with an insecticide if you notice an insect infestation, especially if boring insects produce holes in the tree's weak trunk or branches.