Catalan architect Antoni Gaudi used no straight lines in his creations, including the towering Sagrada Familia church in Barcelona, Spain, pointing out that nature never used straight lines either. Hydrangeas (Hydrangea spp.) evidence his claim. Everything about the deciduous bushes is rounded during the growing season, from the saucer-shaped leaves to the pompom flowers to the melting-snowball shape of the bushes. In winter, however, these garden favorites are not quite as overflowing or attractive.
The hydrangea clan lists at least 23 card-carrying members, but only a few figure prominently in gardens in the United States. The most popular species is bigleaf (Hydrangea macrophylla) that produces the large, globular flower clusters known as mopheads. The clustered stems create a bush some 6 feet tall and wide. Panicle hydrangea (Hydrangea paniculata) grows 10 to 15 feet tall. Both oakleaf hydrangea (Hydrangea quercifolia) and smooth hydrangea (Hydrangea arborescen) are native to the United States. Hydrangeas thrive in U.S. Department of Agriculture plant hardiness zones 4 though 9.
The hydrangeas grown in this country are deciduous, losing their leaves in the winter. Once flowering has ceased and the leaves have fallen, the bare hydrangea stalks stand naked until the following spring. While nature does not remove hydrangea stems in winter, misguided gardeners often do, eliminating the denuded stalks as an eyesore by pruning them back severely. This practice, however, reduces or eliminates blossoms in those species that flower on the prior year's growth, including bigleaf and oakleaf hydrangeas. Panicle and smooth hydrangea flower on current year growth, so severe winter pruning is less devastating.
Hydrangeas are garden survivors, growing in most soils and locations. Your hydrangeas will do best, however, if planted in moist, well-drained soil in a location that is shaded during the heat of the day. Bushes grown in full sun or in hot climates require frequent irrigation to flower and the bright blossoms of bigleaf fade to pastel colors. Too much shade can also limit flower production. Full shade is most damaging for panicle hydrangea, the species that tolerates the most sun. If flower production in your hydrangea suddenly drops off, look closely at its garden neighbors to see if their new growth may be blocking the shrub's access to sunlight.
If those long bare hydrangea stems are getting on your nerves or the plant is simply outgrowing its space. you can prune your hydrangeas as long as you do it appropriately. Mature hydrangea plants will be fuller and healthier if you remove about one-third of the oldest stems each year at ground level. Undertake this pruning while the plants are dormant. To control the height of your plants, prune bigleaf and oakleaf hydrangea directly after their last blossoms have faded. You can trim back panicle and smooth hydrangea stems at any point from late summer until just before the leaves appear in early spring.
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