By Julie Christensen
Mimosa trees, also called Silk trees, are native to Japan and Iran. In the U.S., they are winter hardy only in U.S. Department of Agriculture plant hardiness zones 6 through 9. Even there, they are usually short-lived, succumbing to branch breakage and disease in 10 to 15 years.
From April to July, in areas with mild climates, you’ll see mimosas (Albizia julibrissin) in bloom. The white to pink blossoms have a sweet fragrance that attracts bees and their airy, cotton-like form makes them a glorious sight to behold.
Mimosas are commonly grown along fences or as patio trees. Their lacey, fern-like foliage, fast growth and open, umbrella-shaped canopy make them popular landscaping trees. Unfortunately, mimosas have a few liabilities that you should know about before planting them. Mimosas develop flat, bean-like pods from late summer to fall. These pods, along with the leaves, create quite a bit of lawn litter. The branches and twigs break easily in stormy or windy weather. Mimosas have shallow roots that grow within the top 2 feet of the soil. These shallow roots make it difficult to transplant larger mimosas. They also sometimes emerge above ground, where they damage sidewalks and patios.
In addition to a propensity for disease and insect problems, mimosas are invasive in moist, humid climates, such as Florida. The flowers float on wind or water, carrying seed great distances. Because mimosas are so adaptable, they readily self-sow in the wild, often outcompeting native vegetation. Many communities have placed bans on planting new mimosas because of their potential for invasiveness.
Despite their shortcomings, southern gardeners love mimosas. They grow best with moist, well-draining, light soil, but they tolerate both clay and sand, as well as alkaline and acidic soils. They don’t grow well in salty soils, making them a marginal plant for coastal areas.
To start a mimosa, buy a potted nursery plant, if they’re available, or start it from seed yourself. Soak the seeds in water overnight. Plant them outdoors when daytime temperatures are at least 65 degrees or sow them indoors in a light potting mix. If starting indoors, plant mimosas in peat pots to avoid root disruption when you transplant them outdoors. Plant the peat pot directly in the garden.
Plant mimosas in a sunny location for best flowering and leaf color. They tolerate and thrive in hot conditions. Water newly planted mimosas frequently to keep the soil moist 1 inch beneath the surface. Established trees can tolerate drought conditions, but they’ll perform better with reasonably moist soil. Fertilize the tree every six weeks during the growing season with a ½ cup of 10-10-10 fertilizer.
Mimosas grow 15 to 30 feet tall and 10 to 15 feet wide. Plant them so air circulates freely. Avoid planting them near patios and sidewalks to prevent damage.
Mimosa Pests and Diseases
The major pest of mimosas is the mimosa webworm, the larva of a white or gray moth. Upon emerging from their eggs, the larvae spin a web around the leaves of the trees. They then feed on the leaves, skeletonizing them and causing them to turn brown. In severe infestations, the entire tree can become defoliated by late summer.
Consider planting a different tree if you live in an area where mimosa webworms are prevalent. To control the pests, spray the trees with Bacillus thuringiensis in spring when the larvae first appear. Control is more difficult once the larvae spin webs.
Mimosa vascular wilt is a fatal disease that has destroyed countless mimosa trees throughout the southeast. This soilborne disease is sometimes spread through contaminated nursery soil. Initial symptoms include chlorosis of the leaves. The leaves yellow, while the veins remain green. Later, the leaves begin to drop, branches break and the trunk oozes a frothy liquid. Once infected, you can slow the effects of the disease by watering frequently and fertilizing with a balanced fertilizer. Avoid high nitrogen fertilizers.
For more information, visit the following links:
Albizia julibrissin (Mimosa, Silk Tree) from Fine Gardening
Albizia julibrissin from the Missouri Botanical Garden
Julie Christensen learned about gardening on her grandfather’s farm and mother’s vegetable garden in southern Idaho. Today, she lives and gardens on the high plains of Colorado. When she’s not digging in the dirt, Julie writes about food, education, parenting and gardening.