Mimosa was introduced in the 1700s and is still a popular ornamental tree but it has jumped out of the garden and moved into natural habitats throughout the United States. The tree produces shoots from root sprouts allowing it to form dense thickets which prevents native plants from growing. Seeds are dispersed by animals and through water. It grows best under full sun - so areas along roads and streams are common places for them to grow. The also grow in suburban and urban areas. It is uncommon above 3,000 feet.
The tree (up to 50' tall) is easy to identify in the spring and summer because it produces fragrant, feathery, pink flowers, which resemble pom-poms. In later summer/early fall, it produces oblong, hanging seed pods (6" long).
The fern-like bi-pinnately compound leaves (5 - 8" long) are also distinguishing.
Fact Sheet: Mimosa
Photo credits (left to right): USDA Forest Service - Region 8 - Southern Archive, USDA Forest Service, Bugwood.org; James R. Allison, Georgia Department of Natural Resources, Bugwood.org