a zone question for salvias....
I'm in a microclimate which is 9a or 9b, I'm not sure--SF Bay Area. Normally we get few enough hard frost days to keep citrus alive with minimal protection. But this last winter, courtesy of unpredictable global warming episodes, we had at least 15 hard frost days in a row, and some others scattered in. It killed a couple of patio lime trees and all above ground growth on a 7' abutillon, which are normally survivors here, among other things.
In retooling the garden, I'm thinking of groupings of salvias, especially blues like vitifolia and other vivids like Salvia canariensis var. candidissima.
My understanding of zones is pathetic, but I'm trying to figure out if 'hardy to Z8' means the plant will return the following season only IF it gets enough hard frost; or, if it means if I'm ABOVE Z9, it will likely behave like a perennial anyhow in my garden.
I'm sure different salvias do different things. But I'm looking for some rules of thumb that enhance my chances of a salvia enduring another long frost period OR not, depending on what global warming delivers next year. I don't want to design a garden around plants that won't keep being there.