Stefan Buczacki solves your plot problems
Lyndon Clements, by email
Stefan says: Your question raises several important issues about tree pruning. Your tree is the golden or full moon acer, Acer shirasawanum ‘Aureum’, now about 4.2m (14ft) tall. The canopy has already been reduced at least once and you now want to do it again and you ask when in the dormant season is the best time. The answer is as soon as possible. Unlike some types of tree, which are best pruned early or late in the summer, Japanese maples bleed heavily and pruning should be done before the end of January at the very latest.
If it must be pruned, only do so with care. Take out any dead or moribund branches which will attract coral spot disease, and follow the maxim of not removing more than around one fifth of the total branch growth. These Oriental trees are not as robust as our European maples – field maple and sycamore for example – and may not recover.
You wonder if the work should be spread over two or three years which may seem sensible, although it does mean you will subject the tree to some stress on an annual basis. I’d suggest doing the work over two years but then leaving it for as long as possible.
Finally, you make a most important statement and say you plan to ‘paint over the cut surfaces with emulsion paint to minimise the possibility of disease and die back’. Please don’t do this. It was once believed that painting pruning cuts would help healing. It will, in fact, do exactly the opposite and seal in any bacteria and decay-causing fungi. Cut back the branches to just above the swollen basal collar (never flush with the trunk), and the tissues in this area will gradually grow over the cut and form a natural seal.