Botanical: Hydrangea macrophylla 'Nikko Blue'
Common: Bigleaf Hydrangea
Family: Hydrangeaceae (hydrangea Family)
General Characteristics: This big leaf hydrangea cultivar is part of the hortensia or mophead group (large sterile florets arranged in globular or "mophead"-like panicles). It is a deciduous shrub with a rounded habit which typically grows 4-6' tall. Features clusters of pink or blue florets in large, rounded, 4-5" panicles (corymbs) which bloom in June (often earlier than other varieties) for up to two months. Large, serrate, obovate to elliptic, lustrous, medium green foliage.
Tip: The 'Nikko Blue' hydrangea blooms on large buds formed on growth from the previous season. Because of this, any pruning should be done immediately after flowering. 'Nikko Blue' is best grown in rich, medium moisture, well-drained soil in part shade. Tolerates full sun only if grown with constant moisture. Soil pH affects flower color (blue color in highly acidic soils and pink color in slightly acidic to alkaline soils). Add aluminum sulfate to soil to make flowers bluer or add lime to soil to make flowers pinker (add any such soil amendments to plant root zone in late autumn or early spring). Bloom occurs on old wood. Prune any time after flowering by cutting back flowering stems to a pair of healthy buds. Prune out weak or winter-damaged stems in early spring. Only winter hardy to USDA Zone 5. Can be grown in Zone 5 with winter protection (e.g., mulch and burlap wrap), but may lose significant numbers of flower buds or die to the ground in harsh winters, thus respectively impairing or totally destroying the bloom for the following year.
'Nikko Blue' hydrangea grows best in fertile, well-drained soils. They are not very drought tolerant, and should be watered regularly during dry periods. The 'Nikko Blue' hydrangea prefers full sun, but should be given half shade in areas that have overly hot summers.
Garden Use: Group or mass in a sheltered location of the shrub border. Great cut flower. Also a good specimen or accent for protected locations near homes or patios.