Mimosa, silk tree, is known for its fragrant, showy flowers, delicate leaves and draping canopy. It was imported into the US in 1745, as an ornamental tree. Today, it has been classified as an invasive throughout the eastern and southwestern US. An unusual characteristic of mimosa is that the flowers and leaves close overnight. Changes in water pressure in specialized structures at the base of the petioles and leaflets cause this movement.
I collected the material for this scan from a tree near my home in Easthampton, MA on July 3rd. It is not invasive here.