Pruning Holly
Pruning methods for Holly plants will differ based upon whether they produce berries or not - unless you don't mind whether or not they produce a crop of berries. Holly bushes of any type require no pruning at all, though they respond well to it. The choice to prune is up to you.
Berry Producing Holly Shrubs
Holly shrubs which produce berries in fall, that remain throughout winter, should be pruned in late winter, before new growth begins to emerge in spring. Tiny flowers will be produced early in spring that will then set green berries which eventually turn to red or other colors in fall. Any heavy pruning after flowering will reduce or eliminate berry production.
Non-Berry Producing Holly Shrubs
Here's some basic tips:
Heavy pruning, or rejuvenation pruning, to drastically reduce the size of a non berry producing or berry producing holly shrub should be done in late winter, before new growth has emerged. At this time, if the shrub is healthy, you can cut the plant back by halfway or more and it should sprout new growth from the naked branches/stumps, but there is never a guarantee. Unhealthy plants, which have dead sections, do not respond well to heavy pruning and might be killed or severely damaged by rejuvenation pruning.
Light pruning or shearing to shape or remove a stray or broken branch can be done any time of year.
Shearing of many of the small-leaved holly, such as 'Compacta" and other "crenata" species, respond well to shearing and therefore are suitable for formal hedges.
Tree-Forming a Holly Shrub
Many types of holly, such as Burfordi, Dwarf Burfordi, Needle Point, and some of the taller holly such as 'Fosteri', can be limbed up to form a small to mid-size tree, depending on their mature height. Pruning to tree form should be done in late winter, before new growth has emerged.
Simply start by removing lower branches that would not effect the shape of the canopy and continue upwards until you are satisfied with the shape. Step back every few cuts to view your work.
TIP: Selective pruning holly shrubs with sharp hand or lopping pruners is always recommended. Pruning with electric or gas-powered hedge trimmers can cause unsightly scarring of leaves.
