A very large container with thick walls that won’t crack, and 2-3 inches of insulating material inside the walls can overwinter hardy perennials. Otherwise, the pot should be insulated or sunk into the ground for the winter.
Placing bales of straw for bagged leaves up against all sides and filling gaps with leaves or mulch is one way to insulate containers. Be sure the drainage holes are not blocked, and keep ligularia out of windy locations.
Here are some references for you.
Your Ligularia is beautiful! Thank you for using our services.
Thanks for the compliment and guidance to help preserve this plant through the winter.
You are very welcome.