Ummmmm is the right answer Climbing Season? /forum/images/graemlins/hahaha.gif
Seriously, I think any time is a good time. Each season has its own nuances and variables.
Spring has new and loose bark, summer has high heat and humuggedy, fall fall has blustery and rainy days and winter...well winter sucks but that's not the point. /forum/images/graemlins/grin.gif
I know I've told one of my workers he'll start climbing next spring, but that has nothing to do with training. It has everything to do with opportunity and convenience for me. Too much going on and too short a time before we shut down our northern operations for the winter. He'd have to start all over in the spring anyways.
Between now and when you start for the Boss, read, read & read some more. Go to a climbing wall and gain some practice there. Look up some posts here about starting to climb and SRT and DRT and DdRT and all the rest of the aphabet soup.
Get Tree Climber's companion and maybe even a copy of Sharon Lilly's book on tree work.
Pick peoples brains especially like you've done with this post.