Whether you prefer a natural-looking shape or a neat and formal hedge, cutting an overgrown hedge back into shape is important both for aesthetics and for the health of the plant. At first, you may need to trim the hedge to a smaller size than desired, but eventaully it will reach the right height while maintaining a nice shape and looking healthy. A healthy hedge will enhance your landscaping's aesthetics, and can even increase your home's value.
Wait until early spring to cut an overgrown hedge. It should be trimmed after the worst winter weather is over, but before leaves begin to appear.
Cut away any dead or broken branches using pruning shears. Remove them from the hedge, cutting all the way back to the base or nearest junction.
Decide on a shape and height for the hedge, based on the thickest, healthiest part of the plant.
Trim branches straight along the side, at least 6 inches shorter than the desired final size. More than one pass may be needed if the hedge is especially overgrown in order to remove enough branches and keep the cut smooth and even.
Trim straight across the top of the hedge, cutting it about 1 foot lower than the desired final height.
Shape the sides and top of the hedge, keeping in mind the natural shape of the plant. For example, rounding the top of the hedge may be more in line with the natural shape of the plant, making the hedge easier to maintain.
Allow the hedge to grow to the desired height, trimming occasionally as needed to maintain the desired shape.
Continue to cut the hedge regularly, never allowing the growth to exceed 1 foot beyond the desired size and shape.