- Smooth hydrangeas (Hydrangea arborescens) include old-fashioned favorites such as Annabelle, with its over-size, round, white blooms and new varieties in intense pink. North American natives, smooth hydrangeas flower reliably in U.S. Department of Agriculture plant hardiness zones 3 through 9.1,2
- Panicle hydrangeas (Hydrangea paniculata), also known as grandifloras and Pee Gees, have long, pyramid-shaped flower clusters. New varieties expand color choices from blushing white to deep pink and pale lime. (USDA zones 3 through 8)
- Bigleaf hydrangeas (Hydrangea macrophylla), known as French or florist types, have rounded “mophead" flower clusters or “lacecaps" of tiny bud-like blossoms ringed with showy florets. With colors from white to pink, purple and blue, these include old-timers such as Nikko Blue and new rebloomers such as Endless Summer. (USDA zones 5 through 9).
- Mountain hydrangeas (Hydrangea serrata) may have delicate lacecap flowers or smaller, mophead-like blooms. Colors range from white and pink to brilliant purple-blues. (USDA zones 5 through 7/8)
- Oakleaf hydrangeas (Hydrangea quercifolia) are North American natives with cone-shaped flower clusters and lobed, oak-like leaves. Blooms range in color from white to deep, rosy red. Fall foliage spans yellow-bronze to deep burgundy. (USDA zones 5 through 9)
- Climbing hydrangeas (Hydrangea petiolaris) become hefty, soaring vines, easily covering large walls and sturdy supports. Their lacelike white flower clusters complement appealing cinnamon-red bark. (USDA zones 4 through 8)
- Sun: Hydrangeas thrive in lightly shaded locations, but they still need four to six hours of daily sun to flower well. Plant hydrangeas where they'll get gentle morning rays and shady protection from intense afternoon sunlight and heat. Too much shade limits flowers.
- Soil: Hydrangeas flourish in well-drained, moisture-retentive soil. Soggy or overly dry soil won't do. Adding organic matter such as earthworm castings at planting time improves aeration, enhances water retention and benefits in other ways. Pennington Fast Acting Gypsum helps loosen compacted soils and improve water penetration. Pennington Ultragreen Plant Starter with Vitamin B1 also helps, by reducing transplant shock as newly planted hydrangeas settle in.
- Water: Hydrangeas need plentiful water to hydrate their leaves and blooms. Water to keep soil cool and consistently moist, not overly wet or dry. A layer of organic mulch, such as compost, helps keep soil cool and protect shallow hydrangea roots from drying out. Test your soil by feeling it before you water.
- Food: Hydrangeas rely on solid nutrition for luxurious blossoms and leaves. A complete, balanced fertilizer such as Pennington UltraGreen All Purpose Plant Food 10-10-10 at planting lays the foundation for health and beauty. To encourage more flowers, try Pennington UltraGreen Color Blooms & Bulbs Plant Food 15-10-10.
Smooth hydrangeas and panicle hydrangeas form buds and flowers on brand new stems each summer. Cold winters can kill them to the ground, but they'll shoot back with “new wood" and lavish summer blooms. Prune these types back to one-half their size right before spring growth begins. This encourages new stems, which means more flowers.
Most other hydrangeas bloom primarily on old stems. Flower buds form during summer months, overwinter on stems, and bloom in late spring to early summer on “old wood." When stems are pruned — by you, cold weather or browsing deer — you lose some or all of your blossoms. If pruning is needed, do it immediately after flowering.
A few select bigleaf and mountain hydrangeas bloom on both new stems and old. These reblooming or “remontant" varieties have a showy flush of early flowers on old wood, and then new stems bud and flower from summer into fall. Even if winter damages old stems, you still experience summer blooms. Other than removing dead or damaged wood, these varieties flourish with little or no pruning at all.
Bloom colors for most varieties in these categories shift between blue and pink depending on aluminum, an element that naturally occurs in soil. In low-pH, acidic soil, hydrangeas can take up aluminum and blooms lean toward brilliant blue. High-pH, alkaline soil limits available aluminum, and petal colors trend toward bright pink. At pH levels in between, flowers can turn striking shades of pink, blue and purple.
You can celebrate whatever color your soil and hydrangea create, or you can play with bloom colors on these hydrangeas by testing your soil to learn its pH. Your county extension agent can help. Let the testing laboratory know you're growing hydrangeas, and they may tailor soil amendment recommendations. Products such as Pennington Fast Acting Lime increase soil pH for pinker blooms. For bluer blooms, products such as Lilly Miller Ammonium Sulfate 21-0-0 or elemental sulfur help lower soil pH. Maintaining pH and color changes requires regular reapplications.
Whatever types of hydrangeas grace your garden, you can enjoy the enduring beauty of healthy, prolific shrubs for years to come. Pennington and Lilly Miller are here with timely email tips and premium lawn and garden products to help you grow gorgeous hydrangeas and beautiful, productive gardens and lawns.
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1. Smith, K., Chenault, J.A. and Tilt, K., “Hydrangea," Auburn University.
2. U.S. Department of Agriculture, “USDA Plant Hardiness Zone Map."