Culture
Easily grown in average, slightly acidic, dry to medium moisture, well-drained soil in full sun to part shade. Best in full sun in the northern part or its growing range, but appreciates some afternoon shade in the St. Louis area. Tolerates a wide range of soil conditions. Prune as needed immediately after bloom and no later than mid-August. Plants may be cut close to the ground in early spring to rejuvenate. Plants often struggle in the hot and humid summer climates of the deep South in USDA Zones 8-9.
Noteworthy Characteristics
Physocarpus opulifolius, commonly called ninebark, is an upright, spreading, somewhat coarse, deciduous, Missouri-native shrub which is closely related to the 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.
'Donna May' is a compact selection of ninebark that features colorful foliage, exfoliating bark, and a rounded, dense, well-branched growth habit. Mature plants will reach up to 4' tall with a similar spread. The foliage reaches around 1.5" long and 0.5" wide and retains its dark maroon-purple tinge throughout the growing season. Rounded, 0.75" wide corymbs of small, pale pink flowers bloom from late spring into early summer. This plant is protected by patent number PP22634.
Problems
Fireblight, powdery mildew, and leaf spots may occur.
Uses
Mass in shrub borders. Effective as hedge, screen or for erosion control on banks. Native plant garden. Able to grow in harsh conditions.