Spirea (Spiraea) plants are hardy, deciduous-leaved shrubs. The leaves are simple and usually short stalked in an alternate (i.e. spiral) arrangement. In most species, the leaves are lanceolate (narrowly oval) and about 1 to 4 inches (2.5 to 10 cm) long. The leaf margins are usually toothed, occasionally cut or lobed, and rarely smooth. Stipules are absent.
The many small flowers of Spirea shrubs are clustered together in inflorescences, usually in dense panicles, umbrella-like corymbs, or grape-like clusters. The radial symmetry of each flower is five-fold, with the flowers usually bisexual, rarely unisexual. The flowers have five sepals and five white, pink, or reddish petals that are usually longer than the sepals. Each flower has many (15 to 60) stamens. The fruit is an aggregate of follicles.