DIY tree trunk using Great Stuff spray foam (it's cheaper at Walmart than Lowe's. They're found in the spray paint aisle), concrete tube molds (Lowe's Home Improvement), and spray paint (Rustoleum Camouflage is best, no gloss). Easy to do but the foam is super, super sticky and I highly suggest using rubber gloves. Hold the tube on its side to form your lines and go slowly. Allow to set for at least a day before you paint them. The paint will expand if you don't allow the foam to set correctly.
Halloween Props - Make paper mache trees Two 2x4 (or 1x4 or even 1x2) boards per tree. Scrap plywood to be the base Box of Screws or nails (having wood glue helps) chicken wire Newspaper Paint - black, brown, and gray spray paint Flour and Water for the paste Tools: hammer, drill, measuring tape, and a saw, staple gun, wire cutters, scissors