Jill, all my ground orchids are in pots. I have found that they prefer very well-draining potting soil, so I use my typical potting mix but add 1/3 cypress mulch by volume. They get watered twice-a-week by my irrigation sprinklers and if they look dry, I will water them when I water my orchids, staghorns, and tillandsia that are up in the trees. They are all on ground-platforms, under my oak and cedar trees. Some will get early morning sun and some will get late afternoon sun.
This is my first year to grow Bletilla, and thus have no experience with them being outside over the fall and winter months. I will know a lot more next year because I plan on leaving out a good many of them this year. That's how I learn..........by doing.