Norway maple (Acer platanoides) is a very common tree in the south of Finland. There were two big maples in the garden of our old house and each year new shoots would start to pop up all over the ground underneath the big trees. A few I took and planted into the ground and left to grow there for 3 years. During the winter the rabbits would come and eat away the brackets. We moved house at the end of last year so had to dig them up if I wanted to bring them with me.
The size of the leaves are quite big and I am told that they are not easy to reduce, but I will at least work on them and let's see what happens. If nothing else it will be good practice doing the normal tasks (trimming, pruning, repotting etc.) that is required to make a normal tree into a bonsai style.
The tree below is possibly the variety "Crimson King" which has dark purple leaves. Believe it or not the tree had been the ground the same amount of time as the above two maples but has only grown 10 cm in height.
All these trees were removed from the ground in October 2008 and potted into these pots. I understand that this would not be recommended to do so late in the season, but it was either that or leave them for the new owners to maybe dig up and destroy anyway.