Michael Tierra L.Ac., O.M.D., Founder of the American Herbalists Guild

http://www.planetherbs.com/specific-herbs/albizzia-the-tree-of-happiness.html

The flowers and bark of the mimosa tree (Albizia julibrissin) are among the most valued of Chinese botanicals for relieving anxiety, stress and depression. Commonly found growing throughout temperate zones in the Western United States albizia is native to China, Persia, Korea and Japan. It is traditionally known as "huan hua" (flowers) and "he huan pi" (bark) and popularly as the "happiness herb," and "collective happiness bark" by the Chinese. Recently some Chinese herbalists and acupuncturists have even called it 'herbal Prozac. Its use was first documented in the Shen Nong Ben Cao (Divine Husbandman's Classic of the Materia Medica) during the 2nd century for its mood supportive and calming properties as well as a tonic. Chinese people traditionally recommend its use for anyone who is suffering from grief as a result of a severe loss.
Both the bark and the flowers of albizia are used as a calming sedative in Oriental traditional medicine. Categorized in the Chinese Materia Medica as a calming spirit herb, the bark is thought to 'anchor' the spirit, while the flowers lighten it. The flowers have also been used for the treatment of insomnia, amnesia, sore throat, and contusion in Oriental traditional medicine (Kang, et al) as well as depression, melancholy and anxiety.
Considering the proliferation of antidepressant drugs throughout the Western world with their increasingly recognized adverse effects, it's wonderful that nature has, in abundance, a safer and better alternative probably growing in close proximity to one's doorstep. In my opinion, albizia offers a more profound effect in treating depression and anxiety than the two most commonly promoted herbs, St Johnswort (Hypericum perforatum) and Kava (Piper methisticum) and thus should be more widely used.

(ref. Wikipedia)...
The Mimosa SEEDS are also used as a food for livestock and by wildlife, and the sweet-scented flowers are a good nectar source for honeybees, humming birds and butterflies.

(I added the website because I have only inserted part of the lecture here. Further reading is recommended because it is highly informative and interesting!)