Pruning Guide for Acers - Japanese Maples
In an ideal world, there would be no need to prune your Acer.
Generally speaking they are fine without being subject to the
secateurs. But as with
many shrubs that do not actually need pruning, we sometimes have
a need to prune.
Other than formative pruning for those Acers which go on to make
large shrubs or trees, the Acers and Japanese Maples in particular are
best left alone. The main exception to this non pruning is the removal
of dead and dying branches which have succumbed to the cold in the
If Acers – or Maples – are planted in the right position, and do not
suffer overcrowding from other shrubs, then the least done by way of
pruning the better. The
problem with positioning Acers is the fact that most are bought as
relatively small shrubs, with a general habit of slow growth, so
planting in the ‘right’ position often means gaps to be filled around
the newly acquired plant. Even those bought with the intention of being
‘specimens’ somehow seem to need the protection of a few small shrubs –
or simply a covering up of the bare earthy around.
Being reluctant as we are to remove these ‘sheltering’ shrubs
once they have grown and turned into smothering rather than sheltering,
the Acer suffers, and the secateurs are seen as the only answer.
Pruning Japanese Maples – Acer japonicum types.
Most of the mails I get about pruning Acers are generally about the
Dissectum varieties, which have decided upon their own course of action
- or direction of growth when planted in a rock garden or container.
Acer palmatum Dissectum - and its many different cultivars, are normally
dome-shaped shrubs with a very uniform habit of growth. However, when
planted as a specimen in rock garden or container, they often veer off
to one side – and invariably not the ‘side’ you wish.
Pruning is sometimes seen as the only course of action. This is often
the wrong thing to do, for if you cut a sizeable section of the Acer
away, you still have a root system below ground, that wants to support
the size of plant is has become part of.
It will keep finding and sending its food reserves to try and
re-grow the plant as soon as possible.
New growth – if it happens – invariably starts again on the removed
side, and in a short time the shrub is again trying to assume the shape
that it wanted in the first place.
It is far better to allow the Maple to grow the way it wants if at
all possible, and to alter the surrounding and aspect to suit!
If any pruning is done, then it should be carried out during late,
and in any event before the early spring sap rising. Again, the
exception is if there is any damaged wood after a severe winter.
How and When To Prune Acer Trees.
Regardless of all the
preceding information and advice, someone, somewhere, will want or need
to prune their Acer or Japanese maple. We accept that the world is not
always ideal – so this is how to do it.
Pruning Mature Acers
Acers sometimes fall into neglect, normally by way of being planted
in the wrong position. Life happens and the Acer has to be saved.
Acer trees, normally have quite a dense canopy of foliage and can
be a nuisance – casting shade over large or unwanted areas of the
garden. They do not normally respond too well to having a large central
leader taken out. This often leads to dieback over a few years.
However, lateral branches – other than the ones that emanate directly
from the main trunk, can be removed or reduced in order to curb the
spread of the tree. Many tree Acers are in any event upright in growth
habit, so such pruning can allow light to penetrate through the tree
canopy to the garden – or house below.
Formative Pruning of Tree Acers.
Most newly bought Acers which are ultimately to form trees - Acer
cappadocicum; Acer platanoides; Acer pseudplatanus etc. will have had
their central leader removed, to allow the start of a branching hait by
the two opposite buds - which will then form branches. If this is not
the case, then simply cut back the central leader to two strong buds, to
allow for this to happen. Further formative training of this type can
take place by pruning the central shoot of the laterals. Bear in mind,
that this will then be aiming towards a dense foliage canopy if carried
too far. Far better to allow the lateral side shoots - branches - to
spread out and allow for a relatively open centre of the tree as it
When to Prune Maple Trees
Always carry out such pruning in late Autumn or Winter. NOT in the
early spring or summer. By all means decide in the summer which branches
are going to be troublesome - make a note - and do the work later.
The reason for this dormant season pruning, is that Acers bleed their
sap if pruned in the spring or summer. (So much so, that some Acers are
actually grown for the purpose of sap collection!). It is said to make
Pruning Small Acer Trees and Shrubs.
If the steps are followed below for the Japanese
Acer group, then it is possible to open up the
centre of the shrub - which might be good if it is a
large specimen. The resultant form can be attained
over several years of light formative pruning. Much
of the beauty of the Maples is their branch
structure - other than the beautifulo foliage for
which they are normally grown.
Often after severe winters, there is a case for
cutting out damaged shoots and branches on Japanese
Maples. Sometimes this winter damage does not show
through until leaf break time in late Spring. Simply
cut the dead wood back to a pair of live sprouting
buds - about 2cm - 1in above.
This group of shrubs rarely need anything other
than the lightest pruning (a) to bring back the shrub
into a more desired shape, and (b) to take out 'rogue'
crossing and week shoots.
In this diagram, you will see some 'crossing'
shoots and a few small twigs - which if allowed to
grow - will spoil the shape of the shrub.
In the summer growing season, it is a good idea to loosely tie a
little tape or string where you think best to prune for the desired
shape in the coming Autumn.
This diagram shows the proposed pruning cuts at the red marks - to
sort out the few potential problems mentioned above.
The aim should simply be to open up the centre of the shrub. This is
more preferable for Acers, so that the attractive branch form can be
Always make the pruning cut back to within a few inches of the main
branch. There will be a little dieback of the stub, but this is normally
self-healing and does not require any of the tar based pruning
The pruning has been done! 2 further small branches
on the right hand side could be pruned to give an
'instantly better' shape, but I would wait to see what
sprouts on the left and side to even things up a
The least done to this group the better! If really necessary, can be reduced in size at this
time of year, but far better to allow it to grow to its proper
maturity. Most of the foliage growth will be around the perimeter of the
branches - so there will be plenty of room to under-plant attractive low
growing shrubs or perennials.
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By David Hughes -