2. Spiraea salicifolia Linnaeus, Sp. Pl. 1: 489. 1753.
Bridewort, willowleaf meadowsweet
Spiraea amena Rafinesque
Shrubs, 10–20 dm, ˂thicket forming˃. Stems erect to ascending or spreading, rarely branched. Leaves: petiole 2–6 mm; blade narrowly rhombic to rhombic or lanceolate to narrowly elliptic, ˂usually widest at middle˃, 3–7 × 1–3 cm, ˂length 3–5 times width˃, chartaceous, base acute, margins sharply serrate to serrulate nearly to base, ˂number of primary and secondary serrations 1 times number of secondary veins (excluding inter-secondary veins)˃, venation pinnate craspedodromous, secondary veins not prominent, ˂regularly terminating in primary teeth, inter-secondary veins usually 1–4 per leaf˃, apex acute, abaxial surface mostly puberulent, adaxial glabrous. Inflorescences mostly terminal, cylindric to obconic panicles, 5–10 × 2–4 cm ˂height 2–5 times diam.˃; branches ˂sometimes in axils of leaves˃, puberulent or glabrous. Pedicels 3–6 mm, puberulent or glabrous. Flowers 4–7(–10) mm diam.; hypanthia hemispheric, 0.8–1 mm, abaxial surface glabrous or sparsely puberulent, adaxial glabrous; sepals ovate, 0.8–1 mm; petals pink, elliptic to widely obovate, 1.8–2 mm; staminodes 0; stamens 28–32, 2 times petal length. Follicles oblanceoloid, 4 mm, glabrous, ˂adaxial suture glabrous or ciliate˃.
Flowering Jun–Aug; fruiting Jun–Sep. Old homesteads in moist areas, flood plains; 0–300 m; introduced; Ont.; Ga., Ky., Mich., Miss., N.C., Vt., Va.; e Europe; e Asia; introduced also in w, c Europe.
Spiraea salicifolia is escaped from cultivation in northeastern North America. K. Sax (1936) reported a specimen of S. salicifolia as tetraploid; it is possible that it was not a European specimen, so this count may be unreliable.
The name Spiraea salicifolia is often misapplied to individuals of S. alba var. alba or S. alba var. latifolia (see discussion above). In addition, being a cultivated species that has been popular in gardens and likely introduced and escaped in various hybridized forms, the intermediates and potential hybrids with native taxa can make identification difficult. For problematic specimens that appear to be hybrids, see A. J. Silverside (1988, 1990).