By Pip3
United Kingdom 
We have an Acer palmatum for about 17 years. It has always been about 6ft tall with lots of leaves. This year it has suddenly shot up to around 8 ft, and in places instead of leaves we have some shoots which look like sycamore also growing on the shoots. The tree does not look healthy. Is this something which will disappear or are the trees days numbered?
23 Sep, 2014
Answers
and as autumn approaches the leaves will change colour and fall.
seeds are good and will not harm the tree. they will fall away of their own accord.
23 Sep, 2014
A lot of the Japanese acres flowered and fruited this year… possibly because we had such a good summer last year. This could also be why your acer has suddenly shot up two foot in one year. Come November we are going to have to very severely prune one of our acres as it has got totally out of hand.
23 Sep, 2014
The 'shoots which look like sycamore' are seeds - the tree's obviously flowered and has now produced seed, and all acer seeds (sycamore is an acer too) look like this. As for 'not looking healthy' I can't see enough of the tree to make a judgement about it, and you haven't described any symptoms you're seeing, so more information please. Are the few leaves which are visible in the photo normal leaves for your tree? A photo from further away, showing more of the tree, might be useful too.
23 Sep, 2014