(October) I have a Japanese painted fern, which is
approximately three years old, in a flower bed around a tree. The tree sucks all
the moisture from the fern. I would like to move it to an area where moisture
retention would not be so difficult. When is the best time to transplant? What
type of soil do they like? If I put it in a pot over the winter, would it
survive?
I would move it this fall. Most of the hardy ferns prefer the ground to a pot. I would go ahead and get it planted, so you can have a well-established root system next spring. Make sure you plant it in a well-amended soil and water. It would over winter in a container, provided you protected the container during cold weather, and monitored its water needs. Long term, planting in the ground is best.