I made "puff ball" trees in just a few minutes by using the furnace filter technique

http://royhoffman.com/pwrr/fftrees

I left the skewer trunks out and just used one layer of filter material.

Here they are planted on a mountain along with other furnace filter trees as well as Super Trees and Lichen. They blend in nicely and since they're easy to make, I'll be able to load the mountain up with trees. It's a Pennsylvania mt., so it needs a lot of trees. They'll eventually provide a nice balance of color as well.