When you picture hydrangeas, you think of large puffy blue, pink or white flowers. These are big leaf hydrangeas that have been popular shrubs for years, especially in the South. Oakleaf hydrangeas differ in that they have cone-shaped flowers that grow in clusters and leaves that look like oak leaves. They bloom a little later than big leaf, but the blooms last much longer. Oakleaf hydrangeas are hardy in USDA planting zones 5 through 9.
Water the shrub thoroughly twice a week throughout the first spring through fall. This will allow the root system to become established in its new location. Once-a-week irrigation is sufficient in the following years unless it is very hot and dry.
Apply a slow release fertilizer once you start to notice growth on the shrub and each spring thereafter. Follow the manufacturer's directions as to how much fertilizer to apply given the size and age of the hydrangea.
Spread a 3-inch layer of shredded pine bark in a 3-foot diameter under the shrub. The mulch will help to retain moisture and keep the weeds from growing.
Place a 2-inch layer of organic compost over the mulch each year in midsummer. The compost will leach through the mulch and into the soil with regular watering, supplying needed nutrients to the shrub.
Cut off dead or damaged branches as soon as you notice them. Oakleaf hydrangeas do not need to be pruned for health or shape, but if you prune to keep it the shrub to a certain size, do so right after the flowers fade.