The answer to 'how to maintain hedge' is to regularly trim and prune your hedges to keep them looking neat and tidy. This involves using sharp, clean pruning shears or hedge trimmers to cut back the sides and top of the hedge, removing any dead or damaged branches, and shaping the hedge to your desired look.
It's best to trim hedges in the spring or early summer when the plants are actively growing. Aim to trim them every 4-6 weeks during the growing season to maintain their shape. Be sure to dispose of the trimmings properly and avoid cutting the hedge too severely, which can damage the plants.