Shrub to 1.2 m tall Leaves: alternate, short-stalked, 3 - 7 cm long, egg-shaped to oblong or lance-shaped with a pointed tip, toothed, minutely wrinkled above, white or reddish brown beneath with dense hairs and prominent veins. Flowers: borne terminally in a narrow branched inflorescence (panicle) 5 - 20 cm long with six to ten flowers per cm, pink to purple (rarely white), with five reflexed sepals, five petals, and stamens longer than the petals. Fruit: firm and dry, breaking open along one side (follicle), hairy, diverging, with tiny oblong seeds. Twigs: brownish and hairy.

Similar species: Spiraea alba differs by having more or less hairless leaves, spreading sepals, and hairless fruit. Spiraea x billiardii has hairless fruit. Spiraea prunifolia has an unbranched inflorescence (umbel). The more eastern variety, Spiraea tomentosa var. tomentosa, has eleven to twenty flowers per cm of inflorescence.

Flowering: mid July to late September

Habitat and ecology: Rare in our region, growing in moist thickets, bogs, very sterile sandy areas bordering marshes and bogs, and acidic soils.

Occurence in the Chicago region: native

Etymology: Spiraea comes from the Greek word speiraira, a plant used to make garlands. Tomentosa means "densely wooly." Rosea means rose-colored.

Author: The Morton Arboretum

From Flora of Indiana (1940) by Charles C. Deam

Hardhack requires a slightly acid soil and is frequent to common in the lake area as shown on the map. I have seen areas from an acre to not less than ten acres in extent in low flats where this species was the principal ground cover. South of this area it is absent until the pin oak and sweet gum flats of the southern counties are reached where it is sometimes found but generally in very limited numbers. When a large colony is studied one finds that most of the specimens have elongated and narrow inflorescences but on more vigorous specimens the inflorescences are often spreading. The tomentum on the capsules varies in abundance but the capsules never become entirely glabrous.

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Indiana Coefficient of Conservatism: C = 4

Wetland Indicator Status: FACW