I found this great tree stencil on a site where I would not normally look for stencils, Urban Outfitters! It's always fun to discover a stencil or two being offered from an off the beaten path source. This stencil is not found in their stores, but can be ordered online here. It is currently on sale, reduced from $125 down to $79.99. (plus $5 shipping).
The stencil is very large, 30" wide by 70" high, one overlay.
I recognize this design! It’s the large Birch Tree from Stencil 1. They also offer two smaller sizes.
Agh! stencil is no longer available at UO - will try at Stencil 1