1/48 Scale trees???

I'm building a dio of the Fallschirmjäger boarding the JU 52/3 with support around the plane and such.  I want to put a few trees on the dio but don't know how to figure how tall a tree should be in relation to the plane.  A 6" tree?  What if they were apple trees?  How tall would an apple tree be in relation to the 1/48 scale plane?  I will probably use pine or white birch trees, but still don't know how tall they should be.  Any ideas will be much appreciated!