My neighbor has 4 apple trees that are planted in a square about 2 feet apart. They are definitly designed to grow in the shape of a column rather that the traditional shape. She says they are different varieties, however the fruit of 3 of them looked very similar last summer. She asked me to prune them, but I have never seen this style of apple tree before. They are between 8 and 10 ft tall, and the first side branches are also growing upwards from about 3 1/2 ft from the ground. Should they be topped? Should the branches be thinned out? How far apart should branches be? Any other advice?