Pruning Primer - Shearing
Shearing (or hedging) is the lopping off of all branches at the same height. It causes new growth to develop in all directions from just below the cut, and produces a leggy, top-heavy shrub. Shearing is almost never appropriate except in topiary and to create formal hedges with smooth geometric shapes.
To prevent the top of a formal hedge from shading the bottom and causing weak growth and loss of foliage, the hedge must be wider at the base and taper gradually upward. A well proportioned formal hedge 5 ft (1.5 m) tall can be 2-3 ft (0.6-0.9 m) wide at the base and only 1 ft (0.3 m) wide at the top. Or, it could be 3-4 ft (0.9-1.2 m) wide at the base and 2-3 ft (0.6-0.9 m) wide at the top. Formal hedges pruned to a flat-topped pyramid in this way will maintain foliage all the way to the ground.
Squared or rounded formal hedges and topiary should be pruned in the dormant season and also several times during the growing season - whenever they need it.
Steve Christman 3/6/01; updated 12/26/03, 9/21/15