Common Name: false spiraea
Type: Herbaceous perennial
Family: Rosaceae
Native Range: Eastern Siberia
Zone: 5 to 7
Height: 2.00 to 3.00 feet
Spread: 3.00 to 4.00 feet
Bloom Time: July
Bloom Description: White
Sun: Full sun to part shade
Water: Medium
Maintenance: Medium
Suggested Use: Hedge, Naturalize
Flower: Showy
Culture
Best grown in moist, organically rich, well-drained soils in full sun to part shade. Thrives in sandy loams. Tolerates somewhat poor soils. Prefers cool summer climates and does not perform well in hot and humid conditions south of USDA Zone 7. Somewhat intolerant of urban pollution. Generally requires little pruning. Prune if needed from late fall to early spring (flowers appear on current year's growth). Promptly remove root suckers to avoid unwanted spread. Propagate by stem cuttings, seed or digging up root suckers.
Noteworthy Characteristics
Sorbaria grandiflora, commonly called false spiraea, is a small, suckering, deciduous sub-shrub of the rose family that typically grows to 2-3' tall but will spread, sometimes aggressively, by root suckers and self-seeding to form colonies. It is native to eastern Siberia. It is noted for its attractive summer flowers and odd-pinnate foliage. It was once included in the genus Spiraea (flowers are similar but foliage is different), hence the common name of false spiraea.
Attractive five-petaled white flowers (each to 1/2") in flattened few-flowered corymbs (to 5") bloom at the stem tips in July. Flowers turn a less than attractive brown after bloom. Each odd-pinnate leaf (to 8" long) features 7 to 21 sessile, serrate-margined, lance-shaped leaflets (to 3" long and 1" wide). Leaves are reminiscent of the odd-pinnate leaves of some mountain ashes (Sorbus). Downy shoots are reddish gray. Bark on mature stems exfoliates. Flowers give way to capsule-like fruits (dehiscent follicles) which split open when ripe (fall) to release seed.
Genus name is derived from the genus name of a related rose family member called Sorbus (mountain ash) in probable reference to the similarity of the leaves.
Specific epithet comes from the Latin words grandis meaning large and folia meaning leaf in reference to the large leaf size.
Problems
No serious insect or disease problems. Susceptible to bacterial fireblight.
Uses
Flowers bloom in mid-summer when few other shrubs are in bloom. Shrub borders. Informal hedge. Best when planted in groups or massed in areas where shrubs have room to naturalize without encroaching on other plants. Bank cover for ponds/streams.