These well known, traditional hydrangeas were introduced from Asia before the turn of the century. Most of the Asian species of hydrangeas have either a large ball or cone (panicle) of flowers or a flat lacy cap of flowers. You can find hydrangea flowers in colors ranging from blue to pink to lime green. There are dwarf varieties like 'Pinky Winky' and varieties like 'Endless Summer' that bloom from spring through summer.
There are two species of hydrangea native to North America. Oakleaf hydrangea has huge clusters of cream-colored flowers that last into summer and turn a dusty pink. The foliage turns burgundy-red in fall. If the 8-feet tall varieties are too large, try one of several dwarf cultivars available. Smooth hydrangeas have small domes of white flowers. A new pink variety, 'Invincebelle™ Spirit' was recently introduced. Both smooth and oakleaf hydrangeas have pretty, exfoliating bark in shades of tan and cinnamon.
There is even a hydrangea that climbs to more than 50 feet. This slow-growing hydrangea has sturdy stems that will climb a post or brick wall, clinging with small aerial roots. It features flat-topped clusters of white flowers in early summer. The flaky tan bark provides winter interest in the landscape.
Most hydrangeas like morning sun and afternoon shade. Climbing hydrangeas and oakleaf hydrangeas tolerate more shade, and the lacecap and panicle hydrangeas prefer more sun. Plant hydrangeas in well-drained soil where they will receive adequate moisture. The roots will rot in heavy or water-logged soils, but they will wilt if conditions are too hot and dry. Once established, hydrangeas will thrive for years to come. Give them a little slow-release fertilizer or compost in spring and mid-summer.
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For hydrangeas with pink or blue flowers, the flower color may change depending on the amount of aluminum present in the soil. Add aluminum sulfate to change the color from pink to blue and make sure the soil is around pH 5.4. There are also some varieties that are more likely to stay pink or blue independent of soil conditions.
For hydrangeas that produce flowers on new growth such as panicle hydrangeas and smooth hydrangeas, cut them back in fall or winter. These hydrangeas generally bloom in mid-summer. The spring-flowering hydrangeas like the mopheads, lacecaps and oakleaf hydrangea bloom on old growth. They should be pruned after the flowers begin to fade but before next year's flower buds are set. Prune before August to be safe. For all hydrangeas, you can rejuvenate the plants by cutting back some of the older, thicker stems at the ground.
Article by Sylvan Kaufman. Dr. Kaufman is a writer of popular scientific and gardening articles. She is also an ecological consultant.
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