Shrubs, subshrubs, or herbs, perennial (Aruncus); unarmed. Leaves alternate, simple or pinnately compound; stipules absent; venation pinnate, sometimes palmate. Flowers: perianth and androecium perigynous; epicalyx bractlets absent or present; hypanthium shallowly bowl-shaped, hemispheric, campanulate, patelliform, moreorless crateriform, or turbinate; torus absent, minute, or thickened; carpels 3–5 (or 6) [–8], distinct, free or adnate to hypanthium base, styles moreorless terminal, distinct; ovules 2–5, apical, collateral or clustered. Fruits aggregated follicles or achenes (Holodiscus); styles deciduous or persistent, not elongate.

Distribution

North America, Mexico, Central America, South America, Eurasia, widely

Discussion

Genera 8, species ca. 130 (6 genera, 25 species, including 3 hybrids, in the flora).

The two genera not present in North America north of Mexico are the southeastern European-western Asian Sibiraea Maximowicz (five species) and the Mexican Xerospiraea J. Henrickson (one species).

The base chromosome number for Spiraeeae is x = 9.

Selected References

None.

Lower Taxa

Aruncus, Holodiscus, Kelseya, Luetkea, Petrophytum, Spiraea

Key

1	Herbs, perennial; flowers unisexual; hypanthia shallowly bowl-shaped.	Aruncus
1	Shrubs or subshrubs; flowers bisexual; hypanthia hemispheric, campanulate, patelliform, +/- crateriform, or turbinate	> 2
2	Subshrubs; leaves 2–3(–5)-ternate, primarily crowded basally.	Luetkea
2	Shrubs; leaves simple, cauline (tightly clustered in Petrophytum)	> 3
3	Leaves deciduous, herbaceous, membranous, chartaceous, rarely coriaceous; stems erect, arching, or ascending, sometimes spreading to prostrate in Spiraea	> 4
3	Leaves persistent, often marcescent, coriaceous; stems prostrate (mat-forming), sometimes ascending or erect in Petrophytum	> 5
4	Fruits aggregated follicles; inflorescences panicles or corymbiform or racemiform; carpels free; petals greenish, yellowish, white, pink, or purple.	Spiraea
4	Fruits aggregated achenes; inflorescences panicles; carpels adnate to hypanthium base; petals usually white, sometimes pink tinged, rarely pink.	Holodiscus
5	Inflorescences panicles; petals white; stamens 20–40.	Petrophytum
5	Inflorescences: flowers solitary; petals pink to pinkish, often purple tinged; stamens 7–12.	Kelseya

"thin" is not a number.