Giant false spiraea

Spiraea kirilowii Regel in E. Regel and H. S. T. Tiling, Fl. Ajan., 81. 1858; Sorbaria arborea C. K. Schneider

Plants 15–70 dm. Leaves: blade 14–35 × 8–17 cm; leaflets 13–21, oblong-ovate, (30–)60–90(–130) × (10–)13–30(–40) mm, abaxial surface with simple hairs to 0.8 mm in vein axils, sometimes also stipitate-stellate, adaxial glabrous. Inflorescences (7–)20–30(–42) × (5–)10–17(–33) cm. Pedicels (and axes) usually glabrous. Flowers 5–9 mm diam. (anther tip to tip); hypanthium glabrous; sepals ovate-rounded, margins entire; petals orbicular, 1.9–3.5 mm diam.; stamens 20–25, those opposite petals 1–1.5 mm, others 1.9–2.5(–4.5) mm; ovaries glabrous or nearly so, styles 1–1.2 mm. Follicles 3–5.3 mm, glabrous or nearly so.

Flowering Jun–Jul. Roadsides; 10–400 m; introduced, Wash.; Asia (China, Japan, Korea, Tibet); introduced also in Europe.

Sorbaria kirilowii is cultivated in the United States and Europe, persisting and becoming naturalized in northwestern Washington.