Flowering Silk Trees

The showy mimosa, or silk tree, is native to Asia.

The showy, fast-growing silk tree is also known by the scientific name Albizia julibrissin or, most commonly, as mimosa. With its unique, colorful flowers and elaborate foliage, it can be a striking ornamental, but many botanists and gardeners consider it an invasive pest. Another exotic tree, Ceibia speciosa, is sometimes known by a similar nickname, silk floss tree, but it is less common in the U.S. (It was formerly called Chorisia speciosa, before botanists amended the species name.)

History

The mimosa is native to Japan and mainland Asia.

The mimosa was introduced to the U.S. in 1745 as an ornamental. It is native to eastern and central Asia, with a range from Japan to Iran. Silk floss trees, on the other hand, are native to Latin America.

Identification: Mimosa

The mimosa's botanical connection with peas is apparent from its seed pods.

Mimosas are legumes, related to peas and beans--family Fabaceae. Its compound leaves superficially resemble those of ferns, and are typically five to eight inches long and three to four inches wide; the fragrant, pink-and-white flowers resemble delicate pom pons and cluster on the ends of branches. Long, flat seed pods ripen in August but may remain on the tree until December. Mimosas are deciduous, reaching 20 to 40 feet tall with thin, smooth bark.

Identification: Silk Floss Tree

The "silk floss" of Ceibia speciosa resembles this cotton, but its fibers are too short to spin into thread.

Ceibia speciosa is a member of the botanical family Bombacaceae, related to the tropical baobab and kapok trees. It grows to 35 to 50 feet tall with a broad canopy and nearly horizontal limbs. It bears palmate compound leaves and five-petaled pink flowers, but its most striking feature is its unusual greenish-gray bark, which is covered with thick, tough thorns. It produces eight-inch, pear-shaped fruits; inside the woody coating is the cottony floss which gives the tree its common name.

Geography

Mimosas thrive along American roadsides.

Mimosas may be found cultivated throughout the U.S., and the USDA reports that they are naturalized throughout the mid-Atlantic, Midwest, Southeast and Southwest regions, including parts of New England and the Great Plains. Mimosas thrive in a variety of conditions, from dry to wet, but prefer full sun. Though rarely found beneath forest canopies and at high elevations, mimosa grows abundantly in open areas like vacant lots and roadsides. Silk floss trees, on the other hand, are much more rare, requiring subtropical conditions; they are naturalized only in Puerto Rico.

Benefits

Herbalists recommend mimosa tea as a mood-lifter.

Both "silk" trees are chiefly cultivated in the U.S. as ornamentals, for their showy blooms; mimosa blooms are also valued for their strong, sweet aroma. Mimosas are also edible; the flowers and bark can be used to make a medicinal tea, considered to have a calming, mood-lifting effect. Draco Natural Products' newsletter explains that the active ingredients are saponins and tannins.

Warning

Despite its beauty, the mimosa can be an invasive pest plant.

Despite its beauty and popularity in some parts of the country, silk trees are widely considered invasive pests. Because it reproduces both by seed and by root spread, mimosa can grow into dense clumps that choke out native plants by taking up available light and nutrients. The Plant Conservation Alliance, under the auspices of the National Park Service, has placed mimosas on its "Least Wanted" list. According to the National Forest Service, it is particularly widespread in the District of Columbia and 11 states: Florida, Georgia, Kentucky, Louisiana, Massachusetts, North Carolina, New Jersey, South Carolina, Tennessee, Virginia and West Virginia. The silk floss tree, ceiba speciosa, is not considered invasive.

Prevention/Solution

Use of pruners, hand saws or chainsaws is the first step to eradicating invasive mimosa.

Controlling mimosa will likely require more than one step, because of its aggressive growth habits and adaptability. The Plant Conservation Alliance recommends cutting as a first measure, especially if trees have started flowering. Use a saw to cut the young trees at ground level. You can destroy larger specimens by girdling, and seedlings can simply be pulled out by hand. This removal will slow the plant's reproduction by disrupting the seeding cycle, but you will almost certainly need to apply a chemical herbicide, because mimosas can regrow from cut stems or broken roots. As with any invasive plant, the earlier you can disrupt mimosa's spread, the better your chances of controlling it.

References

• Plant Conservation Alliance Alien Plant Working Group Least Wanted: Silk Tree
• USDA Forest Service Weed of the Week: Silk Tree, Mimosa
• USDA Plants Profile: Albizia julibrissin Durazz.
• Local Harvest: Mimosa Seed (Silk Tree)
• Draco Extract Facts: Calm, Cool & Collected, Traditional Herbs for Sleep and Relaxation

Resources

• USDA: Cooperative Extension System Offices
• Chisholm Trail Academy Herbarium: Mimosa (Silk Tree)