Genus: Hydrangea

Hydrangea

Photo/Illustration: 
Courtesy of White Flower Farm
(Hydrangea)
hy-DRAIN-jah
Hydrangeaceae
These shrubs from the Americas and East Asia provide gardeners with a rich source of plants for understory, mixed border, foundation, and specimen planting. They are grown for their large, showy flowerheads, which are comprised of small, fertile flowers and larger, infertile flowers. On some, the wide range of flower colors is affected by pH (producing pink flowers over 6.0, and blue, below). Many species produce attractive foliage and interesting peeling bark with maturity. Hydrangeas are invaluable for fresh and dried cut flower arrangements. 
Noteworthy characteristics:  A rainbow assortment of conical, flat, domed, and terminal flowerheads for garden, container, and vase.
Care:  Grow in moist, but well-drained soil. Sun to partial shade. Provide shelter from drying winds. Pruning practice depends on whether the hydrangea blooms on the current or previous season's wood. ( H. paniculata is the only species that benefits from hard pruning.)
Propagation: 

Sow seed in a cold frame in spring; take softwood cuttings in early summer, hardwood cuttings in winter.

Species, varieties and clutivars for genus Hydrangea

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Blue Enchantress Hydrangea
Hydrangea macrophylla 'Monmar' PP #25,209
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Blue Enchantress® Hydrangea
Hydrangea macrophylla 'Monmar' PP #25,209
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Smooth hydrangea
Hydrangea arborescens
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Smooth hydrangea
Hydrangea arborescens 'Annabelle'
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Invincibelle® Spirit smooth hydrangea
Hydrangea arborescens Invincibelle® Spirit
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Hills-of-snow hydrangea
Hydrangea arborescens ‘Grandiflora'
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Bigleaf hydrangea
Hydrangea macrophylla
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Bigleaf hydrangea
Hydrangea macrophylla 'Mathilda Gutges'
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'Mini Penny™' hydrangea
Hydrangea macrophylla 'Mini Penny™'
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Bigleaf hydrangea
Hydrangea macrophylla 'Nikko Blue'
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Bigleaf hydrangea
Hydrangea macrophylla 'Pia'
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Bigleaf hydrangea
Hydrangea macrophylla 'Variegata'
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Cityline™ Mars hydrangea
Hydrangea macrophylla Cityline™ Mars
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Panicle hydrangea
Hydrangea paniculata
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Peegee hydrangea
Hydrangea paniculata 'Grandiflora'
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'Limelight' panicle hydrangea
Hydrangea paniculata 'Limelight'
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Panicle hydrangea
Hydrangea paniculata 'Tardiva'
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Panicle hydrangea
Hydrangea paniculata ‘Unique’
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Oakleaf hydrangea
Hydrangea quercifolia
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'Little Honey' oakleaf hydrangea
Hydrangea quercifolia 'Little Honey'
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Hydrangea quercifolia 'Ruby Slippers'
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Oakleaf hydrangea
Hydrangea quercifolia ‘Snow Queen’
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Oakleaf hydrangea
Hydrangea quercifolia ‘Snowflake’
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Mountain hydrangea
Hydrangea serrata
Problems: 

Gray mold, slugs, powdery mildew, rust, ringspot virus, leaf spots.