Hydrangea's (Hydrangea spp.) old-fashioned, mophead or lace-cap blooms fill summer gardens with unforgettable, Monet-esque shades of cream, pink and blue. Their alluring summerlong show, however, comes with a cost. Even in cool-summer coastal areas, hydrangea plantings require significant water expenditures. For inland gardeners in Sunset's Climate Zone 9, only oakleaf hydrangea (H. quercifolia) handles the summer heat without skyrocketing water bills. Its thick, moisture-retentive green leaves contrast with large, conical white blooms before deepening to red, purple and bronze in fall. The shrub's flaking, cinnamon-brown bark provides winter color. Grow oakleaf hydrangea as a specimen or in massed plantings.
Planting Oakleaf Hydrangea
Choose a well-drained site with acidic soil, morning sun and afternoon shade. Oakleaf hydrangeas do best with a soil pH between 5.5 and 6.5. Find a spot large enough to accommodate your mature plant's size. Species of bigleaf hydrangeas grow up to 12 feet high. Cultivars may be even larger or only half that size. The spread of these mounding plants equals or exceeds their height.
Loosen the planting site with the rototiller, adding organic compost to provide the rich soil oakleaf hydrangea loves.
Water your hydrangea well. Dig a hole equal to the depth and twice the width of its root ball. Grasp the plant around its base, and slide it from its container.
Trim broken root ends and cut back roots encircling the soil ball with the stem cutters. Center the plant in the hole with its root ball even with the soil surface. Replace the soil, watering and tamping it with your hands as you go to remove air pockets. Water twice more, once when the hole is filled and several hours after planting.
Caring for Oakleaf Hydrangea
Spread and maintain a 3- to 4-inch layer of organic mulch around the plant. Mulching keeps the soil adequately moist and the roots cool.
Continue regular watering until the hydrangea is established and showing new growth. After that, water it during extended dry spells.
Fertilize the hydrangea beginning in late winter of the year following its transplant. Apply 10-10-10 fertilizer at a rate of 1.5 ounces per 10 square feet of soil.
Prune the hydrangea in August, shortly after it finishes blooming. Remove dead branches, and cut one-third of the older stems back to the ground. Regular pruning controls the plant's shape and encourages bloom.
Things You Will Need
- Hose or watering system
- Stem clippers
- 10-10-10 fertilizer
- Pruning saw
- Oakleaf hydrangea seldom has pest problems, but it may attract Japanese beetles. Dusting or spraying with a carbaryl-based insecticide, such as Sevin, controls the pests.
- Planting oakleaf hydrangea in poorly drained soil leaves it vulnerable to Armillaria and other root rots.
- University of California Sonoma County Master Gardeners: Hydrangea quercifolia
- University of California Extension Solano County: Gardening in Solano County
- Auburn University College of Agriculture: Hydrangea
- North Carolina State University Cooperative Extension: Smooth and Oakleaf Hydrangeas
- University of Connecticut Plant Database: Hydrangea quercifolia
- University of Georgia College of Agriculture and Environmental Sciences: Soil Preparation and Planting Procedures for Ornamental Plants in the Landscape
- University of Florida IFAS Extension: Oakleaf Hydrangea
- U.S. National Arboretum: Hydrangea Questions and Answers