Like most hydrangeas, your healthy looking oak leaf hydrangea does not require pruning to keep it healthy. The only reason to prune would be to remove anything dead, diseased or damaged. If your shrub is outgrowing it's place you should consider moving it to a location where it can spread out as it wants to grow up to 10 feet tall and 8 feet wide. It is fine to shape up this shrub a bit by removing any branches that extend way beyond the others by following the wild branch to a joint where it emerges from another branch or from the trunk. Pruning can be done in late spring after you see signs of new growth. Keep in mind like most hydrangeas pruning too much can remove flower buds so you risk having a flowerless shrub. This hydrangea can handle the sun and will showcase more intense fall color when grown in a sunny location. Enjoy the growth more and worry about pruning less. Keep growing, Marianne Binetti