I've looked over a few scientific studies showing that people breath better around trees. (Which if you've been reading this blog you know, supports my view that we don’t really have control over our breathing--the environment itself trumps our intentions.)
I've recently started doing tree practices. Before I describe those, I’ll describe the internal martial arts practices related to trees that many people already know about.
First off is from Yiquan. While standing still hold your arms out in front of you and wrap them around an imaginary tree. Imagine the tree growing, first up, then fatter, then imagine it sinking while you hold it up, then shrinking, then swaying while you hold on to it, then imagine yourself moving it. This is all done invisibly from the hugging-the-tree posture (zhanzhuang).
Next you can practice gathering qi from a real tree. This exercise can be found in many qigong books and was first taught to me as part of Chen style taijiquan. Stand facing the tree with one foot back and do a circular gathering exercise (there are many) as if pulling in a fishing net, or pulling sheets off of a line. (Follow the peng-ji-lu-an sequence if you know it, as in ‘grasping the birds tail.’) While doing this, feel qi coming down the tree into the roots and then rising up behind you into the canopy and then down the tree again in a large circular vertical orbit.
I learned those exercises over 20 years ago, and long ago they became second nature. But they are important.
The new exercises come from George Xu and involve getting right up to a tree and touching it:
Put your hands on the tree and while keeping your spine vertical and your pelvis level rise up, sink down, move in and move out (kua squats if you know them). Next do the same thing but with absolutely no pressure from the hands on the tree nor any lifting off. Then use your feet to do the same thing you are doing with your hands, allow no force or pressure from the feet. This is a method for ridding ones body of jin, structural power. Once your structural power is turned off, and it’s absence is well established, practice melting all tension and internal body sensation down the front of your body to the ground. If you do this correctly a sensation of steam will begin to rise up from the ground. Practice this until it is a continuous sensation, like rain hitting warm ground and creating steam. Next use only this (neidan) feeling to try and pull the tree down, up, in, out, to the side and...twist.