Tree of the Month, July 2022

“Mimosa”, Persian Silk Tree
Albizia julibrissin
by Martin (Mort) Schmidt
for Simply Living

If you’re driving along a city street in July and notice a small tree with pink flowers, take a closer look — it might be a Persian Silk Tree, commonly known as “Mimosa”. As the name suggests, it is native to the Middle East and East Asia, The Silk Tree is not actually a Mimosa, but it is attractive.

Mimosa leaves are pinnately compound, meaning that they have multiple leaflets attached to a common stem at various points. Palmately compound leaves have leaflets attached at a single point.
In Mimosa, like our native Honey Locust, multiple stems are attached to an even larger stem, making the leaves doubly compound or bipinnately compound. The leaflets are elongated, pointed, and approximately ½ inch in length, with the primary vein on one edge of the leaflet. The leaves fold up during rains, and at night, leading to the name “sleeping tree” in some eastern languages.

The Mimosa grows to a height of approximately 50 feet in the southern US, and perhaps 30 near the Ohio River. But it has poor freeze hardiness and seldom exceeds a height of 20 feet in Central
Ohio, because it generally can’t survive the hardest freezes. Mimosas tend to grow with a low, spreading form, much like our native Redbud, and they often have multiple trunks. The bark is rather smooth, with small oblong lenticels, which are pores that aid in gas exchange.

The most distinctive trait of the Mimosa is its delicate pink and white pom-pom flowers. The pink and white silk-like threads are actually the flowers’ stamens, which distribute pollen. The flowers attract bees, hummingbirds, and butterflies. The seed pods are several inches long and resemble
small snow peas. The presence of seed pods tells you that the silk tree belongs to the legume family.

Mimosas are popular landscaping trees in much of the US, and because they aren’t freeze-hardy, they aren’t invasive and are rarely or never found in northern forests. Unfortunately, they are invasive in the South.

Mimosa lumber is occasionally used to make furniture, crafts, and turned objects, but its limited
size and allergenic properties limit its usefulness. Mimosa is rated 4 out of 4 on the Wood Database list of allergenic woods
https://www.wood-database.com/wood-articles/wood-allergies-and-toxicity/.
I know from my own experience that woodworking with Mimosa caused me a great deal of coughing and hacking. Ironically, Wikipedia reports that the pain from stinging nettles can be instantly eliminated by rubbing Mimosa leaves on the affected area
https://en.wikipedia.org/wiki/Albizia_julibrissin. Little information is available on the lumber hardness, but its specific gravity is reported as 0.55 g/cm³, on par with American Walnut. There’s a strong correlation between wood density and hardness, and Walnut has the median hardness on my list of Ohio trees.

According to Alice Thom Vitale’s Leaves in Myth, Magic, and Medicine, young Mimosa leaves were eaten by people in times of scarcity, and they were used for livestock fodder in some areas.