The mimosa tree has green seedpods with brown bean-shaped seeds. The mimosa tree is an exotic tree in the United States and a competitor with native tree species. Fast-growing and with interesting flowers, the mimosa has been a common small ornamental tree for centuries, since it was introduced to America from Asia in about 1745, according to the University of Tennessee Extension.
Mimosa tree, also called silk tree, is a small tree about 20 feet tall at maturity. Its foliage is fern-like in appearance. In spring, the tree puts out small, pink, pompom-like flowers that are about 2 inches wide. Those flowers develop into green seedpods containing brown, bean-like seeds. The pods dry and turn brown, then fall from the tree, which can create a big litter problem for the area underneath.
This tree has an open, spreading habit, with branches and foliage that let light pass through, making it an appealing small tree for patios or other areas where people like to congregate, according to the University of Florida Extension. However, the University of Florida Extension does not recommend this tree, due in part to its brittle wood, which breaks easily in storms, and the roots' tendency toward lifting concrete in the surrounding area.
Mimosa trees require full sun and average soil. The tree is quite drought-tolerant once established but will look better with enough water. To grow a mimosa, simply gather a seed pod and plant the seeds once they're dry. This tree will only grow in Zones 6B through 9B. Its spread can be quite difficult to control, as the seeds remain viable in the soil for up to five years and new trees sprout easily from root remnants in the soil, according to the University of Tennessee Extension.
This tree is considered weedy and invasive in many areas. In some ways, it checks its own spread by succumbing to Mimosa (vascular) wilt, which kills it, but it also readily establishes itself in any disturbed area where the seeds happen to land. Such areas include roadsides, old fields and stream banks. Its establishment along streambanks, in particular, makes it difficult to eradicate, as seeds simply float downstream and germinate where they land. The University of Tennessee Extension recommends several other small understory, native trees instead of the mimosa, including serviceberry, redbud, flowering dogwood, fringe tree and American holly.