Spiraea L.

Shrubs, 1–40 dm; usually rhizomatous. Stems 5–20+, usually erect to ascending or arching, sometimes spreading, prostrate, or decumbent; bark reddish to dark brown, gray, or gray-black, ?exfoliating or not?; long and short shoots present; young stems ?tan or reddish brown to brown?, glabrous or villous. Leaves deciduous (tardily so in S. thunbergii, partly persistent in S. cantoniensis), cauline, alternate, ?dimorphic with shoot type?, simple; petiole present; blade obovate to oblanceolate, rhombic, elliptic, or linear to lanceolate, ovate, or suborbiculate, 1–10 cm, membranous, chartaceous, or coriaceous, margins flat, serrate to serrulate, dentate, or entire, venation pinnate, surfaces glabrous or hairy. Inflorescences mostly terminal or mostly axillary, (2–)3–1000+-flowered, panicles or corymbiform or racemiform, hairy or glabrous; bracts present or absent; bracteoles present or absent. Pedicels present. Flowers opening before or after full foliation, 2–15 mm diam.; epicalyx bractlets 1 or 2; hypanthium usually hemispheric or campanulate, sometimes turbinate or crateriform, 0.5–2(–5) mm, ± densely hairy or glabrous; sepals 5, usually erect, spreading, or reflexed, sometimes ascending, deltate, triangular, ovate-triangular, or ovate; petals 5, greenish, yellowish, chalky, or translucent white, white, pink [rose], or purple, ovate to obovate, suborbiculate, or orbiculate, sometimes elliptic; ?staminodes present or reduced to annulus, nectariferous?; stamens 10–50 in 2–4 series, shorter or longer than petals; torus absent or reduced; carpels [3 or]4 or 5[–8], free, glabrate to tomentose, styles terminal or subterminal, ?stigmas capitate or discoid?; ovules 2[–4]. Fruits aggregated follicles, 4 or 5, cymbiform, ellipsoid, falcate, fusiform, or oblanceoloid, (0.5–)1.5–4 mm, ?coriaceous?, glabrous or tomentose; hypanthium persistent; sepals persistent or deciduous, spreading, ascending, erect, or reflexed; styles persistent or deciduous. Seeds 2–4 per follicle, fusiform to oblong, ?2–4 mm?. x = 9.