Genus Hydrangea

Hydrangea Hydrangea quercifolia 'Snow Queen' Photo/Illustration: Courtesy of White Flower Farm
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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.
Problems: Gray mold, slugs, powdery mildew, rust, ringspot virus, leaf spots.

Species, varieties and cultivars for genus Hydrangea

Hydrangea macrophylla 'Mini Penny™' Hydrangea macrophylla 'Mini Penny™'
('Mini Penny™' hydrangea)
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Hardiness Zones: 1 2 3 4 5 6 7 8 9 10 11

Information provided by Gardener’s Confidence® Collection
This re-blooming mophead features with inflorescences ranging 4-6 inches wide. Their color will be pink or blue depending on aluminum availability in soil. Compact habit with glossy dark green leaves.

Hydrangea arborescens Hydrangea arborescens
(Smooth hydrangea, Wild hydrangea)
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Hardiness Zones: 1 2 3 4 5 6 7 8 9 10 11

Creamy, six-inch flowerheads form flattened spheres above heart-shaped leaves from June through frost.

Hydrangea arborescens 'Annabelle' Hydrangea arborescens 'Annabelle'
(Smooth hydrangea)
(1 user review)
Hardiness Zones: 1 2 3 4 5 6 7 8 9 10 11

Exceptional and enormous creamy flowerheads up to one foot across form billowy, flattened spheres that withstand the rain well. Leaves are large and downy.

Hydrangea arborescens ‘Grandiflora' Hydrangea arborescens ‘Grandiflora'
(Hills-of-snow hydrangea, Smooth hydrangea)
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Hardiness Zones: 1 2 3 4 5 6 7 8 9 10 11

Hydrangea arborescens is a southeastern U.S. native shrub with a rounded habit to 5 feet tall and domes of creamy white flowers over a long period beginning in early summer. The cultivar 'Grandiflora' has larger, showier flowerheads than the species. They grow to 6 to 8 inches across.  

Hydrangea macrophylla Hydrangea macrophylla
(Bigleaf hydrangea, Hortensia, Lace-cap hydrangea, Florist's Hydrangea)
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Hardiness Zones: 1 2 3 4 5 6 7 8 9 10 11

This is one of the most widely recognized species of hydrangeas. It boasts a plentiful number of cultivars. The species is divided into two groups: the Hortensias (or "mopheads") have globe-shaped flowers made up of large male flowers, and the Lacecaps have flattened flowerheads, with central, female blossoms ringed in larger, male blossoms. 

Hydrangea macrophylla 'Mathilda Gutges' Hydrangea macrophylla 'Mathilda Gutges'
(Bigleaf hydrangea)
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Hardiness Zones: 1 2 3 4 5 6 7 8 9 10 11

This compact shrub bears attractive deep green leaves and large, rounded flower heads of deep pink in neutral soil, and intense violet-blue in acidic soil.

Hydrangea macrophylla 'Nikko Blue' Hydrangea macrophylla 'Nikko Blue'
(Bigleaf hydrangea, Florist's hydrangea)
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Hardiness Zones: 1 2 3 4 5 6 7 8 9 10 11

This is a well-loved and vigorous cultivar with large, rounded flower heads of a rich, gorgeous blue.

Hydrangea macrophylla 'Pia' Hydrangea macrophylla 'Pia'
(Bigleaf hydrangea, Florist's hydrangea)
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Hardiness Zones: 1 2 3 4 5 6 7 8 9 10 11

'Pia' is a dwarf Hortensia (or "mophead"), with globe-shaped flowerheads made up of deep rose, 4-inch-wide flowers. 

Hydrangea macrophylla 'Variegata' Hydrangea macrophylla 'Variegata'
(Bigleaf hydrangea, Florist's hydrangea)
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Hardiness Zones: 1 2 3 4 5 6 7 8 9 10 11

This mound-forming shrub has white leaf margins and blue or pink lacecap inflorescences.

Hydrangea paniculata Hydrangea paniculata
(Panicle hydrangea)
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Hardiness Zones: 1 2 3 4 5 6 7 8 9 10 11

This plant produces gracefully arching branches and pyramidal clusters of white, then pink-tinged to dusky purple blossoms.

Hydrangea paniculata 'Grandiflora' Hydrangea paniculata 'Grandiflora'
(Peegee hydrangea, Panicle hydrangea)
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Hardiness Zones: 1 2 3 4 5 6 7 8 9 10 11

Large, sometimes giant white flowerheads reaching 6 to 18 inches long turn pinkish with age. 'Grandiflora' is a fast-growing shrub that can reach 25 feet tall. Hydrangea paniculata is one of the most cold-hardy species. It may be grown as a single-stemmed tree specimen or as a multi-stemmed shrub. 

Hydrangea paniculata 'Limelight' Hydrangea paniculata 'Limelight'
('Limelight' panicle hydrangea)
(1 user review)
Hardiness Zones: 1 2 3 4 5 6 7 8 9 10 11

This variety of the popular panicle hydrangea boasts very large, lime green blooms in mid-summer that turn pink in fall. A deciduous shrub, it grows to 8 feet tall and 6 feet wide with large, mid-green leaves. The blooms make good cut and/or dried flowers, but can be left on the plant for winter interest.

Hydrangea paniculata 'Tardiva' Hydrangea paniculata 'Tardiva'
(Panicle hydrangea)
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Hardiness Zones: 1 2 3 4 5 6 7 8 9 10 11

'Tardiva' is a late-flowering (early to late autumn) cultivar with loosely-packed, sharply pointed white flower heads that turn purplish-pink with age. It is a vigorous, fast growing deciduous shrub that reaches 8 to 12 feet tall.

Hydrangea paniculata ‘Unique’ Hydrangea paniculata ‘Unique’
(Panicle hydrangea)
(1 user review)
Hardiness Zones: 1 2 3 4 5 6 7 8 9 10 11

'Unique' bears 8-inch-long white flower heads that fade to pinkish white. It is similar to, but more vigorous than, Hydrangea paniculata 'Grandiflora'. The cultivar name refers to the shape of the flowerheads; they are broad at the base and rounded at the tip.  

Hydrangea quercifolia Hydrangea quercifolia
(Oakleaf hydrangea)
(1 user review)
Hardiness Zones: 1 2 3 4 5 6 7 8 9 10 11

More drought tolerant than their classic cousins, oakleaf hydrangeas hail from the sandy stream banks of the lower southeastern United States. The coarsely textured and deeply lobed leaves are matte green, turning striking shades of red and purple in fall. In spring, they deliver nickel-size white bracts lined up in dense coneheads. As the summer wanes, the flower heads age gracefully into shades of pink, green, and ecru.

Hydrangea quercifolia ‘Snow Queen’ Hydrangea quercifolia ‘Snow Queen’
(Oakleaf hydrangea)
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Hardiness Zones: 1 2 3 4 5 6 7 8 9 10 11

This cultivar produces 8-inch-long, conical flower heads from early summer on. It is as notable for its distinct, deeply lobed leaves as for its reliably showy, creamy blooms. The foliage produces outstanding fall color and the flowers take on purplish-pink hues when dried.

Hydrangea quercifolia ‘Snowflake’ Hydrangea quercifolia ‘Snowflake’
(Oakleaf hydrangea)
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Hardiness Zones: 1 2 3 4 5 6 7 8 9 10 11

This cultivar has large flowerheads of intricate double blossoms layered on top of one another. It is as notable for its distinct, deeply lobed leaves as for its reliably showy, creamy blooms. The foliage produces outstanding fall color, and the flowers take on purplish-pink hues as they dry. 

Hydrangea serrata Hydrangea serrata
(Mountain hydrangea)
(2 user reviews)
Hardiness Zones: 1 2 3 4 5 6 7 8 9 10 11

This species was formerly grouped with the Lacecap hydrangeas because of its flattened flowerheads that consist of central, small florets surrounded by showy, larger florets. It is similiar to H. macrophylla but is a more compact plant with smaller flowers and leaves.