Old-fashioned as they may seem to those who remember the blowsy blooms in Grandma’s garden, hydrangeas are back in vogue. The Victorians loved them, and now we do, too. This trend is fueled by new selections entering the market annually, not only the bigleaf or hortensia types (Hydrangea macrophylla, 4–6 feet, Zones 6–9), but also Asian panicle hydrangea (H. paniculata, 10–15 feet, Zones 4–7), oakleaf (H. quercifolia, 6–10 feet, Zones 5–9), and wild or smooth (H. arborescens, to 5 feet, Zones 4–9) species, among others. Breeding and selection has focused primarily on repeat bloomers, on ever-larger flowers, and on double flowers.
The genus Hydrangea, now in the Hydrangeaceae family (along with Deutzia and mock orange, all formerly in the Saxifragaceae) is comprised of about 25 species, but only four or five are widely cultivated. Most popular is the Japanese bigleaf group represented by mophead varieties, including ‘Nikko Blue’, white ‘Mme. Emile Mouillière’, and pink ‘Ami Pasquier’. Lacecaps such as ‘Blue Wave’ and ‘Lanarth White’ have more delicate-looking blooming heads. Mophead Endless Summer and lacecap Twist-n-Shout are repeat bloomers, bearing flowers on both last year’s wood and young growth.
Hydrangeas carry both sterile and fertile flowers. The sterile ones have showy sepals that are attractive and colorful. The fertile flowers are somewhat insignificant by contrast, except in the lacecap types, in which the showy outer florets surround a group of small inner ones. Hydrangea blooms are mainly in white, pinks, or blues, sometimes in muddy purples. Bigleaf hydrangeas are sensitive to the acidity or alkalinity (pH) of the soil, and the flower color can be manipulated. Acid soil (low pH, 5.5 and lower) results in blue flowers, while alkaline soil (high pH, 6.5 and higher) produces pink ones. Soil with a pH between 5.5 and 6.5 often results in unattractive hues.
How to grow: Hydrangeas are at their best in part shade, although they do well in sun in northern sites. They are especially good in humid coastal gardens but should be kept sheltered from fierce winds if possible. Fertile, moisture-retentive soil is best. Amend the soil with plenty of organic matter, especially in sandy places. Hydrangea roots do not handle dry conditions well, but transplanting is a breeze should a site prove too dry. This is often the case where they are grown beneath large thirsty trees. North-, west-, or east-facing locations work well providing the plants are not exposed to intense sun. In the South, never neglect to keep them well supplied with moisture.
Pruning is important. Plants that bloom on the wood made last year (bigleaf, oakleaf, and mountain hydrangea, H. serrata) should be pruned right after blooming, to give the plants time to develop flower buds for the following year. In cold-winter areas, buds are often frosted by intense winter cold, resulting in no blooms the following early summer. Panicle and smooth hydrangeas, however, bloom later in the season on growth made the same year. Prune these in early spring.
In the garden: These most glamorous of flowering shrubs are ideal for many places in the garden. Put them in dappled light on the edge of woods or in open clearings. In shrub collections, plant them with spring-blooming bush cinquefoil (Potentilla fruticosa), forsythia, and viburnums along with later-blooming summersweet (Clethra) and butterfly bush (Buddleja) for a long-season display. Inkberry, rhododendrons, and other shade-tolerant evergreens make a good backdrop. Hydrangeas are perfect for enlivening foundation plantings as well, and the North American species are no-brainers for native plant gardens.
Containers and cut flowers: Some of the newer series, such as Cityline and Mystical, were bred for the potted-plant trade. As gift plants they are always welcome, but once planted in the ground they tend to outgrow their space, so think carefully about the site. Hydrangeas are excellent for cut flowers. After clipping, remove most of the leaves and immerse the stems in deep water overnight in a cool place to condition them. Displayed solo in a low bowl or with fillers, such as mountain mint or baby’s breath, they never fail to please. Hydrangea flower heads usually dry on the plant if not cut and often turn rich shades of rose, crimson, and copper. These can be cut and dried for floral arrangements.
A staple of cottage gardens of yesteryear, hydrangeas are cutting-edge in stylish gardens today. In temperate climates, no garden should be without at least one.
Common names: Hydrangea
Botanical name: Hydrangea species, hybrids, and cultivars
Hardiness: Zones 3–8
Conditions: Best in good fertile soil, enriched with compost or other organic material to help retain moisture. Drainage should be good. Avoid windy places where soil is dry.
Bloom time: Summer into early fall
Height: 3–25 feet. Climbing species may climb to 60 feet or more.
Best features: Large beautiful spherical or cone-shape flower heads held at the tip of stems. The showy florets are sterile, while fertile florets are small and relatively insignificant. Attractive bright-green foliage, often serrated along the edge or lobed like oak leaves. Some species exhibit a colorful autumn display.
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