The blue, purple, and pink French hydrangeas (Hydrangea macrophylla) still rule the hydrangea world, but a challenger is coming up fast. New colors and forms, a long blooming season, and an iron constitution makes panicle hydrangea (Hydrangea paniculata) a formidable opponent. You should plant one or two today.
No other hydrangea can match its tolerance of heat, cold, and drought. You can grow it from Canada all the way down to the Gulf Coast (USDA Zones 3-9). It thrives in full, blazing sun and pests don’t bother it. All it requires is good drainage. Because it blooms later than most other species (summer into fall), it fills the gap in hydrangea color.
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The most familiar form used to be “Pee Gee” (H. paniculata ‘Grandiflora’), sometimes called “the crepe myrtle of the North” for its summer bloom and cold-hardiness. It’s often trained into a small tree up to 20 feet tall. Rounded clusters of white flowers slowly age to pink. Recently, it’s been shoved aside by ‘Limelight,’ (above), a sensational shrub that grows 8 to 10 feet tall and wide with large clusters of white blooms tinged green at the top. A compact version, ‘Little Lime,’ grows 3 to 5 feet tall and wide.
In the Pink
After ‘Limelight’ sold like gangbusters, breeders worked to create new selections whose flowers changed from white to pink to red as they age. Some, like ‘Zinfin Doll’, ‘Vanilla Strawberry,’ and ‘Pinky Winky,’ offer flowers that change color from the bottom-up, giving a two-toned effect.
Flower clusters of others, such as ‘Fire Light’ and ‘Diamond Rouge,’ turn from white to pink to finally red at the same time.
Or, at least, they’re supposed to. Having grown some of these in my Zone 8A garden and observed others around the country, it’s my belief that the farther north you live, the more intense and likely the pink and red colors are. Up north, these hydrangeas bloom later and the nights cool off sooner. Those cool nights trigger the color change. If they don’t arrive until late September and the weather is dry, flowers often turn tan instead. They’re still attractive, especially combined with yellow fall foliage.
Unlike oakleaf hydrangea (H. quercifolia) and once-blooming French hydrangeas, panicle hydrangea blooms on new growth. So you won’t lose a year’s flowers to cold winters or pruning at the wrong time. The best time to prune is late winter (removing last year’s dried blooms is optional). Most of the new selections grow 4 to 6 feet tall and wide. Feel free to shorten plants that grow too tall.
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You can plant potted panicle hydrangeas now either in the ground or in large containers. Give them plenty of sun. Plants in the ground will need soaking three times a week during the first growing season and not at all after that. Water those in containers at least every other day during the growing season.