# Blue Hydrangea Varieties
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USDA Zone 5
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Blue Wave is a cultivar that has more cold hardiness than many types of bigleaf hydrangeas, growing into U.S. Department of Agriculture plant hardiness zone 5. Blue Wave grows between 3 and 6 feet in partial shade. Like many types of this hydrangea, if you place it in full sun, you must keep it well watered. Fasan is another cultivar with cold hardiness to zone 5, serving along foundations or as a hedge. Fasan's flowers are lilac or blue in acidic scenarios. The shrub grows to 6 feet and blooms during July and August.
USDA Zone 6
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Otaksa will not survive in USDA zones colder than zone 6. It has the same large leaves -- up to 8 inches long -- as other bigleaf hydrangea cultivars. Otaksa grows between 2 and 3 feet tall, making it useful for planting on patios. Mariesii turns out its blue flowers during June through August. The shrub has variegated leaves featuring white borders. Mariesii will do best in zone 6 in a sheltered location where the wind cannot directly affect it in winter.
USDA Zones 7 and 8
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Maculata's small stature makes it versatile; this hydrangea grows between 2 and 3 feet tall. It too has variegated leaves, with white edges on the foliage. The blue flowers bloom during July into August in USDA zones 7 and 8. Robert is a cultivar that blooms later into the growing season, flowering into September. It also has the added benefit of having bronze-colored foliage in the fall. Robert grows between 3 and 6 feet high, giving you blue flowers when planted in soil with a pH reading of 5.5 or less.
USDA Zone 9
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Hydrangea serrata is a form of bigleaf hydrangea, but a native of Japan, where it grows in damp valleys in hilly areas. This shrub is suitable for USDA zone 9, growing to 4 feet tall. Its flowers and leaves are slightly smaller in relation to bigleaf hydrangea. The flowers occur in June and continue through August. Nikko Blue takes on a rounded form over time. Adding aluminum sulfate to the soil where you plant Nikko Blue or other forms of the bigleaf hydrangeas makes the soil more acidic and enhances the blue tints of the flowers.
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