Unless it is a very young or immature tree, it is highly unlikely a Japanese
maple would double in size in only 20 months - they are notorious for slow
growth even under ideal conditions, typically taking 25 years or more to
reach a mature size.

Rather than attempting to maintain a reduced size in its current location
(never the most desirable solution), it may be preferrable to relocate the
tree to a more appropriate spot where it can be allowed to grow without
interference. If the tree is too large to consider moving, then I would
consider hiring an arborist that specializes in pruning J. maples. One of
their best features is a sculptural growth habit, specially with a mature
tree, and excessive or improper pruning can really negatively impact the
tree's appearance. Nothing is more unattractive than a whacked at J. maple.

Most maples and Asian maples in particular bleed sap extensively if pruned
at the wrong time. I have not encountered permanent damage to trees if
pruned at the wrong time of year, but it can set them back and stressed
trees are much more prone to various disease pathogens. Pruning is best done
when the sap is not actively running - midwinter (December/January) or in
early summer (June, at least in my climate).

I'd visit a good garden center in the area that sells lots of J. maples and
get their recommendations for qualified arborists. Watch carefully as they
thin or head back and shape the tree and learn how best to do this yourself
for the future to encourage correct growth and to avoid disfiguring a
wonderful landscape asset.

pam - gardengal


"djay" wrote in message
news:PURPe.718$qg2.696@trnddc05...
Hello,

I have a Japanese maple that has doubled in size in about 20 months. I
live on the central coast of California and the growing season is very
long here.

There may be many sources for this type of information and if there is
please point me there, but I'm interested in trimming this tree back. For
the area it is growing in, it is becoming extremely large. So I'd like to
trim it back and was wondering how much to trim it back while still being
safe for the tree and when to do so.

I didn't plant it - I "bought" the tree when I bought the house. It's
beautiful and I wish to keep it healthy but managed.

Thanks,

Djay