Boxwood happens to be one of the most common plants around, especially if you consider all the varieties there are. I certainly don’t mean common in a negative sense. Boxwood and all its varieties often serve as the backbone to many beautiful (and functional) gardens.
With Boxwood most people instinctively shear the plant. The vision most of us have is one of perfectly shaped forms. It definitely is at the top of the list when it comes to formal gardens and topiary.
I’d like to suggest two circumstances when “selective” pruning might be the alternative to shearing.
- when boxwood is used in “natural, informal gardens”.
- when boxwood starts to decline because of too dense branching at the outer ends of the main stems.
Boxwood used in natural, informal gardens.
It’s such a reliable, solid performer; I often use boxwood in natural settings. In these gardens the boxwood are pruned selectively by hand to encourage the plant to stay full and strong while keeping a soft, mounded shape.
Dense, outer growth causes decline.
Overtime a constantly sheared (and formal) boxwood can start to decline in health. This could be because of a number of conditions, e.g. poor internal air circulation that could promote disease or insect infestation. The fact is plants naturally are not conditioned to have all their foliage concentrated just on the outer portion of the branches.
To improve or maintain the health of a sheared plant, you can selectively prune out a portion of the dense, outer growth. If done right this will allow more light and air into the interior without causing a dramatic change in the look of the plant.
I’d like to focus on shearing because this is by far the most common way people prune boxwood.
These first 2 pictures show the before and after of a Boxwood ‘Wintergem’ that was sheared.
This is a recently planted boxwood that was sized at 24 – 30″. At this young stage you have the perfect opportunity to set the proper shape for the future of this plant. Although you can often correct misshaped plants, it’s not easy and usually takes 2 to 3 seasons of growth to see improvement.
The fundamental rule in shaping a plant is wider at the base and taper towards the top. There are 2 main reasons for this:
- It’s healthier for the plant because light is better distributed to the foliage.
- Aesthetically it’s more attractive and logical that the plant be wider at the base. You want the plant to appear as though it’s connected and well-anchored to the ground.
In the sketch below I give a couple of typical shapes you would shear plants both the “right” and “wrong” way.
It is not easy to develop these proper shapes with wider bases. Plants naturally grow a little weaker and thinner towards the bottom. Also, it’s been my experience that most people want to cut an equal amount off the plant all over. That doesn’t work!
If you look at the first picture of the unsheared boxwood, notice how the greater amount of growth is concentrated towards the top. The bottom and lower sides naturally have less growth. Now look at the plant sheared in the 2nd picture. The lower portion of the plant was not touched by the shears.
You should develop a system or pattern to how you shear a plant, get good at it, and then repeat that pattern from plant to plant.
I shear plants in a clock-wise direction. I imagine the proper line the shrub should have and follow it. Regardless of how much or how little foliage there is, stay on that imaginary line. If you need a little help and guidance, for the straight lines take a length of wood like a 1 X 2″ (or anything like that). If you just hold it up once in a while to show the line you’re trying to create, it can really help guide you.
You more often see power hedge trimmers today for shearing topiary plants. They are powerful and quick. If kept sharp and in skilled hands they can do some nice work very productively. In unskilled hands…I’d rather not talk about it.
When to shear plants.
Generally it’s best to let the new growth finish and “harden off” a bit before shearing. From a practical sense the plant should not grow much (if at all) after that and the shape should stay nice until the following growth season.
If you happen to trim early, occasionally I have seen new, soft growth scorch a bit if the weather got hot right after the shearing.
On some properties plants might be sheared twice because the owner does not want to wait for the growth stage to completely finish. So it’s done perhaps midway during growth and then again when it’s finally finished.
These are the main considerations when pruning boxwood and many of these points apply to other plants as well. However, it’s so important you consider each plant and their “specific” preferences and requirements. Like so many things, the skill starts with the right knowledge.