One of the most useful pruning jobs you can do in the winter is crown thinning which will let in light to transform a shaded garden. So often garden owners think that tall trees need to be reduced in height because they are shading the garden, but this can only compound the problem. Cutting back branches drastically will result in vigorous regrowth in the spring, creating a denser crown that will cast more even more shade.
More often than not, trees are left to their own devices until they compromise the growth of other plants in the garden. And invariably the increasing height of developing is seen as being a ‘problem’, whereas healthy, well-grown trees are a huge asset. With regular crown thinning and lifting, even large tree specimens can be accommodated in the garden without causing dense shade under them.
I recently went to help out at a school veg garden project, blighted by dense shade cast from trees. But with selective pruning, the amount of overhanging branches and resulting gloom was drastically reduced. Not only did it guarantee more light for the nearby crops in the coming season, but it opened up a view that had been all but hidden.
The difference was plain to see – and that was in winter when there were no leaves on the trees. It’s no wonder that the children’s garden tutor was caught welcoming the light in the ‘after’ photo at the top of this post!
What is crown thinning
Crown thinning of trees involves removing whole branches, along their entire length, back to the main branch or trunk that they arise from. This is much more effective than cutting the whole tree back all over, which would result in dense regrowth over the whole crown.
It is easiest to see which branches to remove during the dormant season – when there are no leaves on deciduous trees. Without foliage, you can assess where there are closely packed branches that will benefit from thinning out. And by tracing the branches back to their origin, it’s simple to select which to remove.
Crown thinning really ‘does what it says on the tin’. It opens up the crown to let light and air through the canopy. It doesn’t aim to reduce the overall height of the tree which will usually compromise its natural shape and form. A thinned tree will still look graceful as well as open and airy, casting only dappled shade underneath.
How to thin the crowns of trees and shrubs
You may be able to take out alternate branches as you work your way around the crown – it is often the most straightforward way on younger specimens. However, where trees have been left untended for years, it may be necessary to make your own selection.
Choosing to cut out the thinner, weaker branches is usually the best approach, aiming to leave between 5 and 7 of the thickest, main branches and removing the rest back to the trunk. Then, working up into the crown, you can take out alternate branches higher in the canopy.
You need to be bold, as well as able-bodied, if you are going to do the job yourself. The amount of prunings on the form of large branches that result from a well-established tree will surprise you. But probably no more than if you cut back the whole crown to halve its height.
What is crown lifting
At the same time, you may find that trees benefit from crown lifting. This involves removing lower branches, again in their entirety, cutting them back to the main trunk or branches where they originate. ‘Lifting’ the crown will also allow light to penetrate underneath the head of the tree – most usefully when the sun is lower in the sky. This is either seasonally in autumn through to spring, or first thing in the morning or last thing in the evening.
So with a combination of thinning and lifting, trees can retained in a more natural shape rather than lopped back into a dense ‘blob’. And don’t forget that large shrubs can often benefit from the same sort of treatment.
And if you don’t want to tackle the job yourself, find a reputable tree surgeon and suggest crown thinning and lifting. Most will be able to advise you on the pros and cons of your particular circumstances.