The oakleaf hydrangea is the only hydrangea native to the US. It grows in the moist shady and acidic soils of the Southeastern US. The oakleaf hydrangea is a slow growing shrub that has a naturally full shape. However, it can grow 15 feet wide and high and may need occasional pruning if it outgrows its space or if one part of the shrub grows faster than the other because of uneven sun exposure.
How to Prune Oakleaf Hydrangeas
Choose a day to prune the oakleaf hydrangea shrub after a blooming period but before the oakleaf hydrangea sets blooms for next year. This will normally be in June or July but no later than August 1.
Step back and look at the shrub to see what limbs need to be removed in order for the plant to retain a natural shape. You will not shear an oakleaf hydrangea as you would a hedge because you will create a lot of top growth and woody undergrowth, ruining the plant's natural shape.
Cut an unruly or out of place stem back to the main limb. Cut outside the collar where the stem meets the main limb or trunk. Cutting flush or even with the main limb will cause a delay in the healing process where disease or damaging insects can enter.
Remove any other dead stems. If you are unsure if a branch is dead scratch the skin or bark with your fingernail and see if any green plant material is exposed. If you see green, the stem is still alive.