Spiraea L.
(W.R.S., D.R.G.)
Deciduous or semi-deciduous, large, sometimes suckering shrubs, not armed; stems usually erect; young shoots often brittle. Lvs usually distributed along stems, sometimes in fascicles on short shoots, usually simple, sometimes lobed, entire, dentate, crenate or serrate, usually shortly petiolate; stipules 0. Infl. a lateral or terminal panicle, corymb or umbel. Fls 5-merous, small, shortly pedicellate, ⚥ or rarely unisexual. Hypanthium cup-shaped or turbinate. Epicalyx 0. Sepals small, connate at base, usually persistent. Petals 5, usually > sepals, ± spreading, white to crimson. Stamens 15-60, inserted on margin of calyx tube. Ovary superior; carpels (3)-5-(8), free; styles (3)-5-(8); ovules several in each locule. Fr. of coriaceous or leathery follicles; seeds several per follicle; very small.
Key
c. 100 spp., N. temperate regions, extending S. to Himalaya and Mexico. Naturalised spp. 4.
Although there are no reports of wild plants, one of the commonest cultivated sp. is S. thunbergii Blume. This Chinese shrub forms a dense thicket 1-2 m high and is often a persistent relic of cultivation. It is easily distinguished from other Spiraea spp. in N.Z. by its linear-lanceolate lvs and its small sessile umbels of white fls in winter and early spring.
