If your oakleaf hydrangea has outgrown its current location, maybe it's time to consider transplanting. Or maybe you're just remodeling your landscape. Whatever your needs, don't be intimidated by this task. A healthy, well established oakleaf hydrangea with a strong root base will tolerate the move quite well. The best time to transplant your specimen is during the fall or early winter after it has lost all of its foliage and entered dormancy.
Choose a brightly lit, well drained location protected from direct hot afternoon sun and high winds for transplanting the hydrangea. These plants enjoy soils that are slightly acidic with a pH range of about 4.5 to 6.5 being tolerated. Allow plenty of room for the plant, which can attain a size of about 10 feet tall and 5 feet wide.
Dig a hole about twice the width and slightly deeper than the hydrangea's rootball. Work some peat moss or compost into the dirt from the hole if your soil is heavy. You can safely incorporate as much as half of the final backfill volume with the supplementary material.
Prune the oakleaf hydrangea as you normally do prior to dormancy in late summer or early fall. Tie the branches of the plant securely together with twine to protect them from damage during the move, if you wish. This will also keep limbs out of your way, rendering a large specimen more manageable.
Cut a circle around the plant with your gardening spade, beginning about 12 inches away from the hydrangea's base. Tip the blade inward and under the rootball with each stroke to gradually work the plant loose enough to be lifted out of the soil.
Plant the oak leaf hydrangea immediately in the prepared hole. Position the plant with the top of the rootball about an inch above the soil surface. Backfill the hole, firming as you go to eliminate air pockets.
Water the newly transplanted hydrangea slowly and deeply to hydrate the roots well and to help settle the soil. Since the plant has gone dormant for the winter, you probably won't have to water it again until spring. At that time, keep the soil evenly moist to help the new transplant become well established.
Apply 3-4 inches of mulch to help protect the oakleaf hydrangea transplant through the winter.