Heading back will stimulate more new growing points. It is a known fact that the terminal bud secrete a growth-inhibiting chemical which move down to the lateral buds. These chemicals prevent the new lateral buds from growing, when cutting back the chemical is no longer available so the lateral buds start to grow. Usually, the buds just below the cut develop more, they in turn will start to manufacture the growth-inhibiting hormone to help prevent the growth of lateral buds farther down the branch.
Flowering shrubs are pruned by thinning out at different levels within the plant and cut the top back. Remove one or two branches all the way back to the ground. This will stimulate new growth from the root system which will help form a new plant. Don’t continue to prune at the same level year after year. If pruning continues at the same level over time a thick outer shell develops shading the inside of the plant, without sunlight the interior branches die. When damage occurs to the evergreen foliage and it dies a big brown-dead area will result. Since the interior of the plant has no live green foliage, the plant will look pretty bad. Don’t prune Japanese Yews and Junipers beyond where there are no green growth. Japanese Yews and Junipers are needle evergreens and they will not grow new foliage in areas where there no green needles. When plants become too large remove the old plants and re-plant. Select the right mature sized plant for the site. Remember, low maintenance is the best answer.
If most Holly broadleaf evergreens and Azaleas are cut back below the green growth, they will re-grow new foliage. Holly broadleaf evergreens are a big part of the landscape in the south. I have seen large holly plants cut back within 18 inches from the ground and re-grow into a new plant. It will take at lease two years before it will look like a shrub again. Some light pruning is required to re-shape the plant into a nice shrub.