As I mentioned in my Mackers post, here is the quick and dirty make your own branches post. This is pretty easy if you're willing to get your hands dirty. I had a stash of skinny PVC pipes in the shop already, so I went out to the store and bought a heat gun for about $25. Came back, hit some pipes with the heat and began twisting, stretching and bending the plastic. When I finished I ended up here. Nothing too fancy, and I wanted them to still be fairly linear. so I didn't do too much. I came in next with some wire and gaff tape and added in some smaller off shoots just by wrapping around the PVC and bending till happy.
Here is where the messy part comes in. Its Paper Mache time! I watered down a bucket of wood glue and started dipping paper towels. You can use just about any I'd bet, or newspaper or anything along those lines, I find that the school variety of brown hand towels are great for this kind of thing. Layer things on until its all covered. Bunch bits up, crinkle things, wrap, however you'd like because that's going to be your bark texture. Let them all sit and dry for a few hours and then you're ready to paint. I just used spray paint because they were a quick gag, but you could spray and then hit them with a brush for some highlights and shadow.
I thought that these would barely last the show, but they've been dropped, thrown around, stacked in corners and generally abused and other than a few tears and rough spots they are still in remarkably good condition. For foliage we had some Christmas tree branches that we just ziptied on. You could use any foliage you want. With brown ties they aren't too noticeable.
And there you have it. Easy, crafty, and without too much expense.