Low deciduous shrubs, usually with stiff wand-like branches. Twigs round or somewhat angled near the nodes, slender; pith small, round, continuous. Buds small, solitary or collaterally multiple, sessile, globose to fusiform, with about 6 scales. Leaf-scars alternate, half-round or crescent-shaped, minute; bundle-trace 1. Inflorescence paniculate or corymbose, persistent through the winter.
Fig. 124. Physocarpus opulifolius.
Fig. 128. Spiraea japonica.
Fig. 129. Spiraea corymbosa.
Fig. 130. Spiraea virginiana.
b. Stems puberulent or glabrous
c. Branchlets of panicle puberulent or tomentulose
c. Branchlets of panicle glabrous
b. Stems very woolly
b. Stems pubescent
b. Stems glabrous
c. Stems simple or nearly so
c. Stems much-branched
1. S. alba Du Roi. Meadowsweet. Wild Spiraea. . Pipe stem. Erect shrub, 0.3-2 m. high; twigs tough, yellowish-brown, more or less angled, pubescent, at least in the paniculate inflorescence. Low ground, Quebec and Vermont to Saskatchewan, south to Missouri, Ohio, and in the mountains to North Carolina (Fig. 125).
2. S latifolia (Ait.) Borkh. Meadowsweet. Erect shrub 3-12 dm. high, with tough yellowish-brown stems; panicles mostly open-pyramidal, 0. 5-3 dm. long, the branchlets glabrous. Low grounds, Newfoundland to Michigan, south in the mountains to North Carolina (Fig. 126).
3. S. tomentosa L. Hardhack. Steeplebush. Stems angled, 1-2 m. high, pubescent with rusty wool; buds solitary, ovoid, short, with several exposed scales. Low grounds, Prince Edward Island to Manitoba, south to Georgia and Arkansas (Fig. 127).
4. S. japonica L. f. Japanese Spiraea. Stems 1. 5m. high or less, with gray or dingy inflorescence; twigs terete; inflorescence corymbose. Introduced from Asia, spreading from cultivation into thickets and somewhat naturalized (Fig. 128).
5. S. corymbosa Raf. Corymbed Spiraea. Stems erect, less than 1 m. high; twigs terete, glabrous, bright red-brown; buds ovoid, solitary, with several exposed scales; inflorescence corymbose. Rocky banks, in the mountains, New Jersey south to Georgia and Kentucky (Fig. 129).
6. S. virginiana Britt. Virginia Spiraea. Stem much-branched, to 1.2 m. high; twigs often glaucous, glabrous or pubescent, more or less angled, inflorescence corymbose. Rocky places, in the mountains, West Virginia to Tennessee (Fig. 130).