First look at tree with default box mapping. If we would apply bark texture on it, it would look like this:
As we can see, texture on the branches has wrong direction, going vertically on the whole model. First of all apply 'unwrap uvw' modifier and uncheck 'Show Map Seam'so we won't see any old seams from box mapping.
Select 'edge' from sub object and choose point to point seam.
You may click two distant verticles to create a map seam between them.
Now you will be able to crate your own map seams which will be displayed as a blue lines. Let's create our first seams like on this picture. Create loop around base of each branch. Continue creating seams on the other branches just like it is showed on picture.
Each branch should have loop on its beginning, and one seam going through whole length. When you have finished creating seams, it is time to use pelt mapping.
Select face and click on Exp. Face Sel To Pelt Seams. Selection will expand to nearby seams, so you must be sure all seams are done correctly.
Next select 'Pelt' then 'Best Align' from the menu and then click on 'Edit Pelt Map'.