You're faced with a horrid-looking formal hedge. Perhaps it's a tangled thicket looming over your head; perhaps it's spindly and full of bare wood. What to do now? Before you resort to the Herculean task of digging the whole thing out, try to rejuvenate it, returning it to a more informal look. If the shrubs grow from a framework of branches, do the job gradually; don't remove more than a third of the growth each year. Begin by thinning out dense outer clusters of twigs throughout the crown; cut each cluster back to a lateral branch. Also remove weak or crossing branches. The next year, continue to remove more twiggy clusters; also remove new growth that's poorly placed. By the third year, the hedge should begin looking more natural.
If the shrubs grow from the base, you can try pruning the hedge right down to the ground, then letting it regrow. Fast-growing deciduous shrubs such as common privet (Ligustrum vulgare) are good subjects for this treatment. Consult a local nursery or your Cooperative Extension Office to find out if a particular hedge can take severe cutting back; if it can't, follow the steps in Salvaging old shrubs for rejuvenating such shrubs gradually.
To begin the process, cut back all growth to about 6 inches above ground just before plants break dormancy in spring. Remove debris and dig out weeds and other plants that have taken root in the area. When new growth emerges, feed with a controlled-release complete fertilizer; then water thoroughly and apply a mulch. Each month for the rest of the growing season, reduce new growth by half to encourage side branching and make the renewed hedge dense. As you cut back, take care to slope the hedge's sides.
Until the hedge reaches its desired height, cut growth back by half each month during the growing season, starting when plants begin growth in spring. Once the hedge is as tall as you want it, clip it at least twice a year, in late spring and midsummer, to maintain size, shape, and density.