Not sure if this is the right place for it, but in case someone finds it helpful here's how I built a tree recently. I started with three different gauges of wire, with the heaviest - about 1mm thick - being cut the shortest. The thinking is that the heavy wire will give bulk and strength to the lower parts, including the first few branches, before it runs out and the finer wires take over at the outer ends of the branches and at the top of the tree. I bundled them all together, making sure all the heavier wires started here and not halfway up the tree. This will form the tree's base The finished framework with some solder to stiffen some of the finer bits, along with filling up some depressions in the trunk... And here it is with some glue - Selley's All Fix which is very pastey...
Great thread by a real expert. See the whole thread at this link. Additional search terms: scenery foam trunk bark