bladdernut, any shrub or small tree of the genus Staphylea of the family Staphyleaceae. All of the 10–15 known species occur in the North Temperate Zone.
The commonest species usually grow to about 3.5–4.5 m (12–15 feet) tall. The trees are admired more for their handsome green foliage than for their rather inconspicuous flowers, which are white, greenish white, or pinkish. The fruit of the bladdernut is a membranous capsule usually with three sides.