Hydrangeas are flowering bushes that reliably bloom every year and are popular as stand-alone ornamentals or grown in rows to form a hedge. There are many varieties of hydrangeas and not all are pruned in a similar manner. In fact, some hydrangeas need little pruning at all. However, the oak and big leaf hydrangea varieties, which are among the most popular hydrangeas, are pruned in the early fall.
Prune in the early fall, right after the hydrangea has finished blooming. If you wait too long, you might inadvertently cut off this year's new growth, which are the limbs that bloom the following year.
Cut off all broken or diseased limbs about 1/4 inch above a node. Use sharp lopping shears or hand clippers, depending on the size of the branches.
Trim off some of the limbs that just bloomed, called old wood. Prune the tallest limbs to shape and some of the middle limbs to allow more sunlight to penetrate and more air flow in the center of the bush. Prune no more than one-third of the old wood in any given year and again, prune 1/4 inch above a node.