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Physocarpus intermedius   (Rydb. ) C. K. Schneider
[=Physocarpus opulifolius  (L. ) Maxim.  var. intermedius  (Rydb. ) B.L. Robinson]
Wildcat Glades, Newton County, Missouri
Height: Shrubs, to 10 feet
Family: Rosaceae - Rose Family
Flowering Period:   May, June
Trunks: Stems spreading to ascending or erect; branches unarmed; bark brown to reddish brown, exfoliating in long, thin strips or papery sheets; wood tan, soft.
Twigs: Yellowish brown, flexible, glabrous; leaf scars shield-shaped; buds brown, ovoid, .1 to .16 inch, apex obtuse, scales sparsely to densely pubescent.
Leaves: Deciduous, alternate, simple; stipules caducous or more or less persistent, linear to narrowly ovate, .2 to .28 inch; petiole .4 to .8 inch, glabrous; blade ovate to obovate, 1.6 to 4.8 inches long, 2 to 3.6 inches wide, base cuneate to truncate or rounded, margins palmately 3- or 5-lobed, irregularly serrate, apex acute, lower surface light green, sparsely stellate-hairy, upper surface dark green, glabrous.
Flowers: Terminal on lateral branches of season, racemes, rounded, 10-30-flowered, .8 to 2.4 inches diam.; peduncles .4 to 2 inches, sparsely stellate-hairy, glabrate; bracts lanceolate to oblanceolate, .08 to .16 inch; pedicels .4 to .8 inch, usually stellate-hairy, sometimes glabrate. Flowersbisexual, radially symmetric; hypanthium shallowly cup-shaped, stellate-hairy; sepals 5, spreading, triangular, .1 to .12 inch; petals 5, white, round to elliptic, spreading to reflexed, .16 to .24 inch long and wide; stamens 20-40; pistils 3-5, connate to half their lengths, free from hypanthium, ovary superior, 1-locular; style 1 per pistil, glabrous; stigma 1 per style, capitate.
Fruit: June-July; follicles, brown, weakly connate at bases, ovoid, more or less inflated, stellate-hairy, .3 to .5 inch, styles persistent basally, spreading to ascending, .16 to .2 inch; seeds 1-2 per follicle, yellow to brown, obovoid, obliquely pear-shaped, .08 to .1 inch long, smooth, shiny.
Habitat: Rocky banks, bluffs, stream banks, woodlands.
Distribution: Southeast corner of Kansas
Origin: Native
Comments: Physocarpus intermedius has been treated as a variety of Physocarpus opulifolius (L.) Maxim. Physocarpus opulifolius is distinguished by its glabrous follicles; it occurs mostly in the eastern United States and is widely cultivated as an ornamental shrub.

Atlantic ninebark inflorescence
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Wildcat Glades, Newton County, Missouri
Atlantic ninebark leaf
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Wildcat Glades, Newton County, Missouri
Atlantic ninebark leaf
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Wildcat Glades, Newton County, Missouri
Atlantic ninebark fruit
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Wildcat Glades, Newton County, Missouri
Atlantic ninebark bark
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Wildcat Glades, Newton County, Missouri
Atlantic ninebark flowering
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Photo by Craig Freeman