The Spiræa tomentosa.

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1832.  The Hardhack, a barren bush, usually chooses poor cold ground for its residence and growth.—Williamson, ‘History of Maine,’ i. 116.

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1851.  A bunch of the white hardhack, a cream-like flower, innerly blushing.—S. Judd, ‘Margaret,’ ii. 1. (N.E.D.)

3