I am in zone 5, but the winter before last was really bad. We had several nights, and even days, that were below zero. One night we even went down to 23 below. Brrrrrr!!! I experiment with mediums, since my garden soil here is VERY clay, so its tough to mix. I try to stay with 50/50 potting mix and garden soil. I even bought top soil to mix in with the potting soil, but it seems the local topsoil is mostly clay, too. My husband and I moved here (Ohio) eight years ago from South Jersey. They don't call Jersey the Garden State for nothing. It was MUCH easier to garden there. The soil was a sandy loam and the temps are much milder. Anyway, I got carried away, when I first found named varieties on the internet. I was going to open a greenhouse, but that fell through. In the anticipation of that, I was buying all the varieties of semps I could get my hands on. I soon found out that one person can have a really hard time managing the 300 plus or minus varieties that I had, plus my other gardens. Between being a dummy, working full time and 2 nasty winters, I am down to somewhere between 125 and 150 varieties of semps, including some heuffeliis and jovibarbas. I have several varieties of the Pacifics that are VERY prolific! I have Pacific Knight, Pacific Devil's Food, Pacific Greensleeves, Pacific Red Rose and Pacific Red Tide all over the place. I have trouble keeping those from crowding out, but I struggle with others. I was on a roll with the Pacifics and was trying to get them all, so I have quite a few. Some hang on, but others like Pacific Zoftic, Dawn, Showboat, Daemon, Teddy, Mauve and Hepsport I can't keep. I have replaced Zoftic 5 times and have lost all but one over the years. That's why I was wondering if they were just not quite as hardy as most semps. I still do want those ones but, if I ever get them back, I think I'm going to build a cold frame for the winter. Also, I had problems with some of them heaving over the winter. A big problem is wind blowing the soil away, because we live on top of a hill. We just went and picked up 3/4 ton of grit, so everybody is getting stoned.
Anyway, that is most of my story, One of these days I'll get a list together.
