A privet hedge regenerates after a hard pruning that reduces the size of the hedge dramatically. Pruning of many species of plants stimulates new growth. The root system stores carbohydrates from the photosynthetic work of the entire canopy of the shrub. When the canopy is cut back, the carbohydrates are used by the plant to generate new shoots.
Hard Pruning: Two Methods
Method 1: "Head back" all stems of the hedge to 4 to 6 inches above ground. This is the technique for complete regeneration. Lightly prune to one even height in the first year.
Method 2: Selectively prune out the largest stems at the ground and prune the smaller stems to 6 inches below the final desired height. The goal is to get rid of the oldest, woodiest stems by selective thinning and "head back" the rest of the plant to one even height. (Use this second method when it's important to keep the hedge barrier during regeneration.)
Use long-handled loppers for removing the thickest stems and hand or hedge pruners for the small shoots in Method 2. For yearly maintenance shearings, use electric or gas-powered hedge shears. The best season to promote regeneration is wintertime, when a maximum amount of carbohydrate has been stored and there is the least shock to the plant.
Privet Hedge Varieties
Privet can be evergreen or deciduous. Some privet are more suitable for large, broad-spreading hedges such as the Regal privet, while others, such as the Amur River, are suitable for clipped hedges in northern zones. For warmer climates, select an evergreen variety such as the California privet. An excellent choice for a compact, slow-growing hedge is the Lodense variety.
There are about 50 species of privet in the genus known as Ligustrum. Privet species are native from eastern Asia to the Malay Archipelago, northwest Australia and North Africa with one species native to Europe. Privet species are members of the plant family Oleaceae, of which the olive tree is perhaps the most recognised member.
Be aware that most privet varieties have been introduced from Asia and may be invasive in American environments. Many are on invasive plant lists in most states in the United States. Birds are attracted to the seeds and spread individual plants.