How to Improve Old Boxwood Hedges

Rejuvenate old boxwood shrubs by pruning away one-third of the oldest growth each spring before the new growth starts to form. Cut one-third of the tallest branches away by pruning them. Remove branches from all over the hedge, including the center, to promote air circulation. Each spring prune away another one-third so by the fourth year the hedge is completely made up of new growth.

Shape the hedge by measuring the desired hedge height on several stakes, which are pounded in the ground next to the hedge. Mark the height on the stakes. Tie a string to the stakes at the mark so you have a straight guideline for pruning. Use pruning shears to cut straight across the guideline so the hedge is at an even height. Shape the sides of the hedge to is it wider at the base than at the top. This ensures the bottom leaves get adequate sun. Shape the plant throughout the growing season, as needed.

Fertilize the hedge in the fall with a granular 10-6-4 fertilizer at a rate of 1 lb. per 100 square feet. Water thoroughly after applying the fertilizer. Add an organic mulch, such as compost, above the hedges root system in the spring. Ensure the mulch is no more than 1-inch thick and that it doesn't touch the hedge's stalks. Boost the soil with a nitrogen fertilizer if the leaves turn yellow and fall off.