This section is from the book "Nature's Garden", by Neltje Blanchan. Also available from Amazon: Nature's Garden; An Aid To Knowledge Of Our Wild Flowers And Their Insect Visitors.
Flowers - Pink or magenta, rarely white, very small, in dense, pyramidal clusters. Calyx of 5 sepals; corolla of 5 rounded petals; stamens, 20 to 60; usually 5 pistils, downy. Stem: 2 to 3 ft. high, erect, shrubby, simple, downy. Leaves: Dark green above, covered with whitish woolly hairs beneath; oval, saw-edged, 1 to 2 in. long.
Steeplebush Or Hardhack. (Spiraea tomen'osa.)
Preferred Habitat - Low moist ground, roadside ditches, swamps.
Flowering Season - July - September.
Distribution - Nova Scotia westward, and southward to Georgia and Kansas.
These bright spires of pink bloom attract our attention no less than the countless eyes of flies, beetles, and bees, ever on the lookout for food to be eaten on the spot or stored up for future progeny. Pollen-feeding insects such as these delight in the spireas, most of which secrete little or no nectar, but yield an abundance of pollen, which they can gather from the crowded panicles with little loss of time, transferring some of it to the pistils, of course, as they move over the tiny blossoms. But most spireas are also able to fertilize themselves, insects failing them.
An instant's comparison shows the steeple bush to be closely related to the fleecy, white meadow-sweet, often found growing near. The pink spires, which bloom from the top downward, have pale brown tips where the withered flowers are, toward the end of summer.
Why is the under side of the leaves so woolly? Not as a protection against wingless insects crawling upward, that is certain; for such could only benefit these tiny clustered flowers. Not against the sun's rays, for it is only the under surface that is coated. When the upper leaf surface is hairy, we know that the plant is protected in this way from perspiring too freely. Doubtless these leaves of the steeple bush, like those of other plants that choose a similar habitat, have woolly hairs beneath as an absorbent to protect their pores from clogging with the vapors that must rise from the damp ground where the plant grows. If these pores were filled with moisture from without, how could they possibly throw off the waste of the plant? All plants are largely dependent upon free perspiration for health, but especially those whose roots, struck in wet ground, are constantly sending up moisture through the stem and leaves.