Forestry & Wildlife
Native to the Middle East and Asia, the mimosa or silk tree (Albizia julibrissin) was brought to the United States in 1785 by French botanist Andre Michaux. Michaux planted it in his botanic garden in Charleston, South Carolina. This fast-growing tree reaches heights of 50 feet. Its pink powder puff-like blooms usually appear beginning in May through July. The flowers, measuring about 1.5 inches long with clusters of silky pink threads, are known to attract butterflies, bees, and hummingbirds. Its leaves have a fern-like appearance which gives it a lacey, delicate look. While beautiful, the mimosa is also a highly invasive species that threatens the southern landscape.
An invasive species is an aggressive, fast-growing non-native species capable of outcompeting most vegetation at a given locale. Invasive species may cause environmental damage by displacing desirable native plants and animals. An invasive species can also change nutrient levels and fire cycles which reduces growth of timber and other crops. Song birds are especially dependent on caterpillars and other insects to feed and rear their young. These food sources are more common on native trees.
Mimosa began as a landscape tree, but it escaped cultivation and is now growing in natural areas across the southeastern United States. It competes with native species for light, water, and nutrients. Mimosa trees can grow in a variety of soil types and can tolerate many moisture conditions. Like many species in the legume or bean family, it has the ability to fix nitrogen. It prefers open conditions and colonizes areas quickly after disturbance removes vegetation and opens up the tree colony. It can be found growing along roadsides, streams, forest edges, in grasslands, vacant lots, and in clearings throughout the south.
Mimosa trees produce an abundance of flattened legumes, each of which contain five to 10 seeds. These seeds contain a neurotoxin which, can be toxic to dogs and livestock if ingested. The seed pods typically remain on the tree throughout the winter months. Mimosa seeds can remain dormant for extended periods of time. The seeds are usually dispersed close to the parent plant, but they can also be spread by wind, water or wildlife. Trees located along rivers increase the ability to transport seeds over large distances. This short-lived tree is susceptible to a variety of diseases and insects such as webworms, mites, vascular wilt disease, shot hole borer, armillaria fungus, and root rot.
Management of invasive species such as mimosa tree is important to prevent spread and continued damage to the environment. Also, as the climate continues to change, it is possible that warm climate species such as mimosa will spread further north. Therefore, good management practices are necessary now. To rid your landscape of mimosa trees cut them at ground level and use an herbicide such as glyphosate on the stump to prevent new growth. Seedlings can be pulled by hand, but take care to ensure all of the roots have been removed from the soil.
Planting native species provides us with an opportunity to protect our forested land. By avoiding non-native, invasive species such as the mimosa tree, we can work to bring back species that naturally grow in the southeast. There are several native species available that have similar form and bloom in the summer. Try planting sourwood (Oxydendrum arboretum). This species blooms in the summer, and the flowers attract both native bees and honeybees. It also displays beautiful fall color. Another plant that blooms in June is buttonbush (Cephalanthus occidentalis). This large tree-like shrub enjoys a moist environment and grows well in wet areas like pond and lake edges. It produces gorgeous flowers in the summer that attract bumble bees and butterflies. Choose wisely and begin enjoying the native beauty of the region.
For more information on the management of invasive species, please consult the following Alabama Extension publications: Cut Stump Herbicide Treatments for Invasive Plant Control, ANR-1465 and Basal Bark Herbicide Treatment for Invasive Plants in Pastures, Natural Areas, and Forests, ANR-1466.