Flower:

Round to dome-shaped clusters, ¾ to 2¼ inches across, of long-stalked flowers at the tips of branches. Flowers are white, ¼ to ½ inch across with 5 round petals. In the center are 3 to 5 pistils with long, slender yellow-capped styles and 30 to 40 slender, spreading, pink-tipped stamens. Sepals are triangular, less than 1/8 inch long, with or without star-shaped (stellate) hairs.

Leaves and stems:

Leaves are simple and alternate, 1½ to 5 inches long, 1 to 3 inches wide, the blades lance-oval to nearly round in outline, mostly 3-lobed (up to 5) with coarsely toothed edges, on a stalk 1/3 to 1 inch long. The upper surface is dark green, lower surface lighter, both either have stellate hairs or are smooth.

Stems are multiple from the base, about 1 inch maximum diameter, branches are upright and arching. One year-old branches are simple, cane-like, forming lateral flowering branches the second year and dying out after several years. New canes develop each year from vegetative buds at the base of older branches. Young bark is brown and mostly smooth, turning gray, older bark peeling in papery strips.

Fruit:

Flower clusters become drooping in fruit and persist through winter. Each flower produces a group of 3 to 5 inflated, 1/3 inch long capsules called follicles, each with a single hard seed inside. The grouped follicles hang in a round cluster, initially greenish red to bright red, drying brown, surfaces are either smooth or have stellate hairs.

The seed is somewhat teardrop-shaped, light tan colored and very shiny.

Notes:

Like many species common to the eastern US, Ninebark's range only creeps into Minnesota's most eastern counties. It is however only occasionally encountered in woodlands, more predominantly found in transition habitats characterized by rocky or sandy soils in full sun to part shade with sufficient moisture. It is easily recognized by the numerous rounded clusters of white flowers or long-stalked fruit, and the slender canes with peeling bark. While not recognized by all botanists, it is separated into two varieties in Minnesota: var. intermedius (a.k.a. Physocarpus intermedius) found in our central woodlands and southeastern bluff country, characterized by spreading stellate hairs on the fruits, and var. opulifolius found along the rocky cliffs and stream banks of the Arrowhead region which has smooth fruit. Var. opulifolius is also noted as having larger leaves than var. intermedius, and larger clusters with up to 50 flowers, where var. intermidius clusters have 15 to 20 flowers. Ninebark is a very durable landscape shrub with numerous cultivars selected on leaf color (gold or red), shrub size (dwarf) and flower cluster size.