I have several hibiscus (probably 2 doz.) I thought I would be moving this year, so I dug up some 1 year plants, and had others that I had wintered last year in their 4" pots. I had a load of dirt brought in, and I put everything in pots, and buried the pots just deep enough for the pot in this soil. I called it my garden to go! The sale of my property didn't go through, and it looks like I might be staying this winter. Are these plants in enough soil so they won't get a deep freeze? We usually have a couple of weeks where it is below zero, and the wind chill can get low for a length of time. They grew well this summer and bloomed! I also have hostas in this garden. Can I mulch heavily? I don't want to loose any of them. Any advice would be appreciated. Thanks.