I took Belle over to the local park this afternoon so that I could show you how we do tree agility. Belle is four years old now, and we've been going to the park since she was about a year old so she could swim in the creek. I started using the trees to teach her to send and to play with handling at a distance. Here is a video of our playtime today.
The great thing about using trees for distance training is that you are much more likely to be playful about it. If your handling is off or your dog fails to interpret your cue, no big deal. Toss the toy or food tube and try again. If the move you tried is too difficult make it easier to be successful: break it down to simpler pieces, decrease the distance, whatever it takes.
Okay, stop reading, and go outside and play with your dog.