Physocarpus opulifolius, commonly called ninebark, is an upright, spreading, somewhat coarse, deciduous, Missouri-native shrub which is closely related to genus Spiraea. In Missouri, it typically occurs along streams, rocky banks, gravel bars and in moist thickets, especially in counties south of the Missouri River (Steyermark). Grows 5-9’ tall (less frequently to 10’). Noted for its exfoliating bark (on mature branches) which peels in strips to reveal several layers of reddish to light brown inner bark (hence the common name of ninebark). Bark provides winter interest, but is usually hidden by the foliage during the growing season. Features small pink or white, five-petaled flowers appearing in dense, flat, rounded, 1-2” diameter, spirea-like clusters (corymbs) in late spring. Flowers give way to drooping clusters of reddish fruit (inflated seed capsules). Ovate to rounded, usually 3-5 lobed leaves (to 4” long) are dull green in summer changing to an undistinguished yellow in fall. Genus name comes from the Greek physa meaning a bladder and karpos meaning fruit, referring to the inflated dry fruits of the plant. Specific epithet refers to the leaves that resemble those of Viburnum opulus. Common name of ninebark is in reference to its ornamental attractive exfoliating bark.