Come late Autumn our trees are going into the dormant period (well at least they should be), this is the time of year to check our trees for general health, and ensure that they get through the winter safely.
As the leaves are falling off our deciduous bonsai it gives us chance to be able to see each individual branch, look for any unwanted bugs, such as scale insect, and treat them before the winter weather kicks in. An old toothbrush works quite well to scrub along each branch, and methylated spirit on a cotton bud dabbed on the little critters also helps to kill them off.
Winter protection is a difficult thing to give clear advice on as this will depend on your situation, and where your trees are kept and where you live. It is important to remember that you almost certainly have trees which survive in the wild without being wrapped up in cotton wool, but by the same token the wild versions also do not have their roots bound into pots! So you have to apply a bit of sense to your protection regime. The main thing is not to allow your trees to remain completely waterlogged. Protecting them from daily, torrential rain will help, but also be aware of rain followed by a very cold night or days of cold weather. The latter tends to do more harm to your pots, causing them to crack, but prolonged rain and cold could be the undoing of your tree. The other big thing is the wind which can dry your trees out surprisingly quickly. Easterly and northerly winds bring a raw coldness with them, that can also do damage and is the biggest killer of maples. Think on maples you may have seen in parks, they are often in dipped or areas protected from the wind. Of course if you are keeping your trees over-wintered under cover, you will need to water them occasionally.