Many plants, including holly, undergo a dormant period during the winter. Knowing when to trim holly bushes matters, especially for your specific location and depending on what species of shrub or tree you have. While it is not necessarily ideal to prune certain plants during their dormant period, it's safe to prune holly at this time though there may be some risks.
What Happens When You Winter-Prune Holly
When you winter-prune a shrub that blooms on old wood, such as holly, you are potentially cutting back on the number of flowers that will appear on the plant during the following growing season. The trade-off can be worthwhile because you are choosing a time to prune that is safe for the plant and it may rejuvenate it. This may be the case if you're pruning overgrown holly bushes that are deciduous. At other times of the year, pruning may leave the plant vulnerable to diseases or spur new growth that will be damaged by frost.
When to Trim Considerations
- The branches you prune off in winter (whether on a male or female holly shrub) carry buds that will not open during the upcoming year, resulting in reduced pollination and fewer holly berries.
- Unlike flowering shrubs that bloom on old wood in spring, holly is not grown for its floral display. Instead of pruning just after the blooming period is over, wait until your holly has flowered and begun to form berries before pruning. This will safeguard your berry production.
- Remember not to prune too late in the summer, because you could generate new growth that would only be killed in the first frosts of fall.
Pruning for Indoors or Outdoors
Part of the fun of growing certain kinds of holly shrubs is in admiring the berries. If you have such a shrub and it is covered in berries come December, would you rather leave the bush intact during the holiday season or bring some branches indoors to decorate your home?
Some people prune holly in early winter since they wish to bring the trimmed stems—with their holly berries—inside for the holidays. Others prune holly in late winter months between January and May, or more specifically four to six weeks before the spring thaw period emerges in your area. Late winter pruning may be preferred to keep the display of holly berries going strong outdoors.
How to Prune Holly
When pruning holly, use bypass pruners, not the anvil style. You should always remove dead, damaged, or diseased branches whenever you find them, and it is generally advisable to cut off a branch that is rubbing against another branch or jutting out in such a way that it spoils the overall appearance of the bush. It's not usually advisable to cut holly all the way back to the ground unless you need to drastically reduce its size or want to try regrowing it to be more vigorous.
Here are examples of a few types of holly with specific pruning tips.
'Blue Princess' Holly
'Blue Princess' holly is a rounded evergreen Meserve hybrid holly. It is a shrub with red berries and dark-green, prickly leaves. You need to get in there and prune this type while it is still young to give it a sustainable shape that you can then maintain as the bush ages. If you skip pruning for a few years while the plant is still young, you may end up with an unmanageable plant later.
Once you do attain a desirable shape on this shrub, it is best to prune sparingly; tip-prune it to maintain shape wherever possible. If you do need to cut further down a branch, be sure to make your cut right above a leaf bud. If, on the other hand, you are forced to perform a drastic pruning on this bush, be prepared for it to look unsightly for a long time.
'Hetz Japanese' Holly
'Hetz Japanese' holly is an evergreen shrub that you may have mistaken for a formal boxwood shrub, and it's also sometimes called boxwood holly. It has tiny leaves that are not prickly, nor is it grown primarily for its berries. Unlike 'Blue Princess,' it is very easy to prune. If you have disease problems with yours, you might want to open up the inside so you can make thinning cuts to help promote healthy air circulation and allow you to continue shaping the plant.
'Sky Pencil' Holly
'Sky Pencil' is another Japanese type, but it is valued for its oddly narrow plant form, and like the 'Hetz Japanese,' it is easy to prune. Depending on your needs and desires, you may not even have to prune it much at all. Pruning should be minimal unless your bush suffers severe damage from snow and ice buildup. The latter can be avoided by wrapping twine or bungee cords around the shrub over winter to pull the branches in tightly toward the plant's center.
Inkberry holly is a no-fuss evergreen holly grown as a foliage plant with berries as a bonus. That quality is precisely why you see mass plantings of it in public places, as it is easy to maintain and shape. Prune simply to thin, shape, and control its size.
Holly also comes in tree form. Examples include American holly, yaupon holly, and Nellie Stevens holly, which are all evergreens. You can shape a holly tree to your tastes by pruning, and some people cut off some lower branches to expose more of the trunk. If you do not want your tree to get overly tall, you can prune back the leader every winter. Be sure to make your cut right above a branch with some good, vigorous green growth on it, because this is your new "endpoint."
Unlike the kinds of evergreen holly presented above, winterberry holly is a deciduous shrub with greenish-white flowers. It is so different from the more typical hollies that you might as well be discussing another plant altogether, especially when it comes to pruning. While drastic pruning is a bad idea for evergreen hollies, it is quite acceptable for winterberry, which responds well to rejuvenation-style pruning. Remove up to a third of the stems each year, targeting the oldest, thickest ones.