Thanks all!
Any advice would be appreciated.
Lynn, I can't say for a fact the differences in survival rates. I'd say it's a combination of a great many factors, like soil, siting, sun, shielded mini zones etc., and all depending on specific cultivars. Also, it is hard to predict what our winters will be like. Sometimes they are really dry, sometimes (like last year) they are a waterlogged mess.
I'm going to go for a really harsh soil mix this year. I thought the soil combo I used was fast draining enough, but I'm going to try even moreso this year.
Then of course next winter will be bone dry...