Physocarpus opulifolius var. intermedius (Atlantic ninebark)

Physocarpus opulifolius (L.) Maxim. var. intermedius (Rydb.) B.L. Rob.

Opulaster intermedius Rydb.

Physocarpus intermedius (Rydb.) C.K. Schneid.

Atlantic ninebark, common ninebark

Kingdom	Plantae	Plants, but not fungi, lichens, or algae
Subkingdom	Tracheobionta	Vascular plants—plants with a “circulatory system” for delivering water and nutrients
Division	Magnoliophyta	Flowering plants, also known as angiosperms
Class	Magnoliopsida	Dicotyledons—plants with two initial seed leaves
Subclass	Rosidae	Roses, legumes, proteas, dogwoods, hydrangeas, mistletoes, euphorbias, grapes, many more
Order	Rosales	Rose family and eight others
Family	Rosaceae	Includes apples, apricots, plums, cherries, peaches, pears, raspberries, strawberries, almonds, roses, meadowsweets, photinias, firethorns, rowans, and hawthorns; many others
Genus	Physocarpus	From the Greek phusa or physa, “bladder, a pair of bellows” and karpos, “fruit,” thus “bladdery fruit”
Species	opulifolius	With leaves like the guelder-rose opulus which was actually a type of maple
var.	intermedius	Intermediate, indicating an observation that a species was probably considered as being halfway or partway between two others with regard to some particular characteristic, e.g. tall, short, and “intermediate”

About plant names...

Atlantic ninebark is native to eastern North America and the prairie states. The plants are found on moist soils in thickets, along streams in sand or gravel bars, and on rocky slopes and bluffs. Michael Dirr (1997) says that “the species is adaptable to all conditions, probably even nuclear attacks, and once established, requires a bulldozer for removal.”

Plants: This shrub has multiple stems resembling grapevines, with peeling bark that is brown when young and turns gray with age. The bark peels in strips, and is the source of the common name ninebark: the apparently inexhaustible supply of bark suggests the plant has “nine lives.” They are 24-84" (60-213 cm) high, with stems up to 1" (2.5 cm) around.

Leaves: Simple and alternate, 1½-5" (3.8-12 cm) × 1-3" (2.5-7.6 cm). Leaves are usually 3-lobed, sometimes 5, linear to narrowly ovate to obovate, dark green above, lighter below.

Flowers: Flowers form round or dome-shaped clusters ¾-2" (1.9-5.7 cm) around at branch tips, with flowers ⅜-⁷/₁₆" (1-1.2 cm) around and 5 round white or pink petals, and 30-40 stamens. They appear primarily in Jun, with fruiting Jul-Sep. (Accounts vary on flowering and fruiting, with some sources listing May-Jul for both flowering and fruiting.)

Fruits: Flat or inflated dehiscent seed pods.

Online References:

Physocarpus opulifolius var. intermedius on (Word document)

Physocarpus opulifolius var. intermedius at Minnesota Wildflowers

Physocarpus opulifolius var. intermedius on Wikipedia

Physocarpus opulifolius var. intermedius on the Encyclopedia of Life

Physocarpus opulifolius var. intermedius on eFloras

References:

Dirr, Michael A., Dirr’s Hardy Trees and Shrubs, Timber Press, 1997

8/2/2008 · Bar Harbor, Maine
≈ 4½ × 3" (11 × 7.9 cm) ID is uncertain

Physocarpus opulifolius var. intermedius description by Thomas H. Kent, last updated 25 May 2020.

8/17/2014 · Bald Mountain, Franconia Notch Area, White Mountains, New Hampshire
≈ 7 × 4½" (18 × 12 cm)

9/24/2010 · Nissitissit River Wildlife Management Area, Pepperell, Massachusetts
≈ 5 × 3½" (13 × 9.2 cm) ID is uncertain

9/24/2010 · Nissitissit River Wildlife Management Area, Pepperell, Massachusetts
≈ 12 × 8" (31 × 20 cm) ID is uncertain

8/17/2014 · Bald Mountain, Franconia Notch Area, White Mountains, New Hampshire
≈ 6 × 4½" (16 × 11 cm)

Range: Zones 2-8:

About this map...