General Culture:
Easily grown in average, medium, well-drained soil in part shade. Tolerates full sun only if grown with constant moisture. Intolerant of drought, with foliage tending to decline considerably in dryish conditions. This species blooms on new wood, and may be pruned back close to the ground in late winter each year to revitalize and to encourage vigorous stem growth and best form. Plants may die to the ground in harsh winters. If not pruned back, any weakened and/or damaged stems should be removed in early spring.
Noteworthy Characteristics:
Hydrangea arborescens, commonly known as smooth hydrangea, is a deciduous shrub with a rounded habit that typically grows 3-5’ tall and features flowerheads (to 6” across) consisting mostly of creamy white fertile flowers. It is native to southern Missouri (see K520). ‘Grandiflora’ is a smooth hydrangea cultivar that was discovered growing in the wild in Ohio around 1900. It produces much showier flowerheads than the species. Large asymmetrically rounded flowerheads (corymbs to 6-8” across) consisting mostly of large showy white sterile flowers bloom in late May to June for up to two months, sometimes with a small repeat bloom in the fall. Dark green, serrate leaves (3-8” long). A Royal Horticutural Society of Great Britain Award of Garden Merit plant (1993).
Problems:
No serious insect or disease problems. Many species of hydrangea, including this one, are susceptible to bud blight, bacterial wilt, leaf spot and mildew, however this cultivar seems to have good resistance to these diseases. Although ‘Grandiflora’ stems are erect and generally considered to be stronger than those of the species, the heaviness of the flower heads, particularly when moistened by rain, can cause the heads to droop to the ground and thus require staking. Pruning stems back to the ground in late winter each year helps promote stem vigor.
Uses:
Mass in a part shade area of the mixed shrub border for long-lasting and often spectacular summer bloom.
© Missouri Botanical
Garden, 2001-2010
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