For those boxwood shrubs shorter than about 3 feet (1 meter): the best time to prune is around April-June and August-October.
So, in short, they are pruned twice, and a tip to remember this is that these are the “A” months, from the letter that the month begins with.
It is possible to prune during other months, too, but not in winter nor during the vegetation phase of your boxwood.
For boxwoods that form a hedge and aren’t being modeled into any specific shape, pruning once before summer is enough.
Note, however, that in some places, for some types of hedges, trimming is unlawful in Spring. This is to ensure birds aren’t disturbed during the nesting season.
Tools needed to prune boxwood
Special scissors or shears have been developed for pruning topiary, they are perfect for boxwood.
For hedge-bound boxwood, any hedge trimmer or long-bladed shears will do fine.
Giving your boxwood a round, conical or other shape
During the first year, start giving your boxwood the shape you’re aiming for.
At the beginning, simply go for the general silhouette rather than pruning in great detail.
It will take you several years before you’ll make it to the final shape.
Afterwards, every time you prune, you’ll only remove a portion of the new growth added since the previous pruning.
As time goes by, your shrub will grow in size but retain the shape that you wish it to have.
Pruning a boxwood hedge
In a hedge, it is important that the lower portion of the hedge be wider than the top, kind of like a narrow pyramid with a cut top.
That is how the entire shrub will receive sufficient light.
If the lower part is thinner than the top, it will grow sparse.
For low-lying hedges, set one plant every 4 to 6 inches (10 to 15 cm), to ensure full density.
Hard pruning of boxwood
Has your boxwood grown too large? Reduce it to the size you need over a few years with the following technique:
Early Spring, cut one in two or one in three branches back to about a foot shorter than your target size (30 cm).
This will make the boxwood look like a swiss cheese with lots of light reaching the center.
New branches will sprout in the center of the shrub.
In Spring of the following year, you can cut back the remaining branches.
From then on, you can trim and prune your boxwood regularly to keep it at a manageable shape.
Cutting the entire tree back in one go might kill the shrub, which is why it’s best to stage it over at least two years (ideally three).
Some people recommend cutting back to a stump. Though some box shrubs do recover, it isn’t at all guaranteed. The gradual reducing of the shrub will make sure it survives.
Janet Caulder wrote on 15 April 2021 at 18 h 28 min
My boxwood shrub has gotten much too big. Can I trim it back to nearly a stump and it come back this season with new foliage?
Gaspard wrote on 23 April 2021 at 5 h 51 min
Hello Janet, in some cases cutting back to the stump works, but there’s also a risk of killing the shrub. Better is to reduce it over two to three years. The article now mentions how to go about this.
In a hedge, it is important that the lower portion of the hedge be wider than the top, kind of like a narrow pyramid with a cut top.
My boxwood shrub has gotten much too big. Can I trim it back to nearly a stump and it come back this season with new foliage?
Hello Janet, in some cases cutting back to the stump works, but there’s also a risk of killing the shrub. Better is to reduce it over two to three years. The article now mentions how to go about this.