I get a lot of questions about different trees and other plants in and around College Park, and someone stopped me on the Trolley Trail on the way back from the Metro yesterday to ask me about this tree.
It’s Mimosa, or Persian Silk-tree, Albizia julibrissin. The feathery flowers are distinctive among our native and ornamental trees. When the flowers fade and seed pods develop, you’ll see the similarity between Mimosa and our native Redbud (and beans and peas, for that matter): They’re all in the legume family. The long pink filaments that comprise the flower are actually the male parts, stamens.
The genus is named after the Italian nobleman Filippo degli Albizzi, who introduced it to Europe in the mid-18th century. Here in the (relative) north, it’s a very short-lived tree, both because it doesn’t handle cold terribly well and because of a fungal disease, fusarium. These keep it from being too invasive here, which it is in some parts of the US and in Japan. It’s best to think of Mimosa as an interesting small tree that casts a light shade but probably will need replacing every 10 years or so. It grows very quickly and blooms when young.
The flowers close up at night and on cloudy days; the finely divided leaves also fold up and droop at night, leading to various common names in other languages: shabkhosb or “night sleeper” in modern Persian; nemunoki, nemurinoki and nenenoki which all mean variations of “sleeping tree” in Japanese.