On our field trip to the Captain Forster Hammock Preserve on 3/3/18, it was heartening to see that nearly all of the invasive East Indian walnut trees (Albizia lebbeck) had been cut down and treated with herbicide. This Florida Exotic Pest Plant Council Category #1 invasive plant was once prevalent at this Preserve and is present at the Oslo Riverfront Conservation Area, at the Florida Medical Entomology Laboratory, and along Oslo Road. It is said to be native to tropical Africa, Asia, and Australian — and to be widely naturalized elsewhere.
Thank you to everyone who plucked pods from one of the large trees left along the trail. Its pods can be more than an inch wide and up to one foot long. The seeds in the pods rattle in the wind and give rise to the unfortunate common name woman’s tongue tree. Pod production can be prolific.
East Indian walnut trees can grow to be 65′ tall and have a thick, dense canopy of leaves. They are related to the mimosa (or silk) tree (Albizia julibrissin), once commonly planted in cooler climes than ours and now known to be quite invasive where it thrives. This plant does not tolerate the warm temperatures in our part of Florida and southward.
Their kinship is evident in their double compound even-pinnate leaves and in their flowers. Mimosa trees have poofs of pink flowers. East Indian walnut trees have yellow or white poofs.
Legumes, plants in the pea family (Fabaceae), fix nitrogen and improve soil quality. Since the area of the Captain Forster Hammock Preserve where the East Indian walnut trees were most common was the area that had been farmed, I began to wonder if they had been planted to improve soil quality, and then I discovered, much to my surprise, Feedipedia, which calls itself an online encyclopedia of animal feeds and is the work of the Food and Agricultural Organization of the United Natures.
It turns out that the foliage, twigs, flowers, and immature pods of this fast-growing tree are used for fodder for camels, cattle, small ruminants, and rabbits. Sheep apparently especially love to eat the flowers. This tree also is used for firewood and timber and is recommended as shade tree for coffee plants.
Its patchwork bark is quite beautiful, but this pest tree is difficult to control — even with herbicide applications. Whenever possible, remove this weed tree or, at least, its flowers or pods.