Q: Often my hydrangeas just don't bloom. Am I doing something wrong?
A: Take a good look at how they're sited. Hydrangeas generally need some sun and like some shade. In the South, nurseries grow them under pines or shade houses to filter sunlight. "For most hydrangeas, the farther north they are, the more sun they can stand," says horticulturist Michael Dirr. "In the South, they can get away with just three hours of sun." Hydrangeas in Southern gardens should be planted in locations with morning sun and afternoon shade; in the North they can do well in full sun as long as they get plenty of water and aren't subjected to dry winter winds. Temperature is as much an issue as sun, particularly for mopheads, which are susceptible to drooping from heat stress. They love a coastal setting, where breezes dissipate the heat, and thrive in the salty air. If full sun exposure and high heat are issues, you might try another old-time favorite, peegee hydrangea (H. paniculata 'Grandiflora'), which can withstand those conditions. If, on the other hand, your yard is short on sun, try oakleaf hydrangea, which prefers partial shade.
Another issue that can affect bloom is a late-spring or early-fall cold snap; the buds on bigleaf hydrangea (H. macrophylla) are particularly vulnerable because they flower on the previous year's growth. If unpredictable frosts are a problem where you live, consider two cold-hardy types: smooth hydrangea, which is native from New York to Florida and as far west as Arkansas; and peegee hydrangea, which is also the most drought tolerant. A popular native, H. arborescens is prized as a reliable bloomer in cold climates.
Last, consider how and when you prune. If you're cutting off more than just dead branches or spent blossoms in fall or early spring, you're removing the old wood, which carries the new season's buds for H. macrophylla "And I always use half the amount of fertilizer recommended on the label," says Dirr. "That way you'll be encouraging blooms and not more leafy growth."
Shown: Usually seen as the classic white 'Annabelle,' this pink 'Bella Anna' (shown) is a brand-new hybrid that reblooms all summer.