Certified GKH Gardening Expert
No matter where you are, you can prune mint at any time of year. This plant is so invasive that it will not hurt it to prune. It will come back even more vigorous.
I do not recommend ever putting mint into ground anywhere that you do not want it to take over. It will, and it will likely choke out any plant that you have planted. Stick to containers with mint, unless you have an established raised bed just for this purpose.