Somehow, and I cannot explain why, after nearly thirty one years in this garden, I am unable to locate micro climates that might support plants that are only marginally cold hardy (I hear you, I’m not too bright). Yes, I’ve tried, and failed, with no discernible patterns. At least, indiscernible to me. One year, maybe I’ve figured it out, but the next, not.
Marginally cold hardy, I take to mean, is that this garden is a half or a full zone too cold for a plant, or more often that a plant is over optimistically rated for cold hardiness that I don’t believe (Case in point, zone 6 gardenias. Good luck). Sometimes with good reason, other times just skepticism. In theory, and certainly in practice despite my failures, there are warm spots (and cold) within the garden. A place that is protected from wind, perhaps with reflected winter sunlight might be several degrees warmer. I’m sure these spots exist, I just don’t know where they are.
There are plants of marginal cold hardiness that survive in this garden, but immediately beside them a questionably zone 7 hardy something or other has failed, sometimes more than once. Now, I grow fatsia, corokia, and illicium, but cover them with leaves or evergreen branches for protection, sometimes at the last minute. I’ve given up on several mahonias after repeated failures, or at least repeated near failures when ‘Soft Caress’ became smaller each year. After the fifth try, and after a stocky shrub diminishes to a few sickly twigs, what’s the point?
So far this winter I can happily say that it’s been mild. Mild doesn’t mean warm, but weeks of highs in the thirties have so far been outnumbered by ones in the fifties, with scattered sixty degree days that tempt me in the morning to dress in shorts and sandals. Certainly, there will be multiple ups and downs before spring. Winter can’t be this easy.
Undoubtedly, there are advantages to living in a climate where below freezing temperatures are typical in the winter months. I can’t think of any at the moment, but there are blooms that require a number of days or hours of cold that don’t happen further south. On the other hand, there are shrubs that I’d love to grow if only winter temperatures were a tiny bit warmer. Or, if I could figure out where the warm spots in the garden are. But, after thirty one years in this garden, it’s fair to expect it’s not going to happen.
Ramblin' through Dave's Garden 
Same problem with mahonia soft caress. Thinking of trying it in a container and bringing it in to the garage in cold nights. Thoughts?
I’ve overwintered several marginal shrubs with an enclosure of chicken wire loosely filled with leaves. I won’t set this up until the cold is forecast since the foliage is damaged by the constant moisture. This would probably have saved Soft Caress.
Gardenias of any cultivar are SO unpredictable. Those who grow them well do not seem to put much effort into it, and do not understand why or how they are so difficult for those of us who tend to them better.
Here, gardenias are very predictable. It’s too cold for them, and ones rated as zone 6a or b were just wrong. We have to grow them in pots and protect them in winter, or don’t grow them. I’ve learned my lesson, and now I have none.
Well, that works. My colleague down south doe not use them at work, but grows them as annuals at home. They sometimes last for many months, with sporadic bloom, but when they start to decline, he wastes no effort on them.
Thanks for this info. The soft caress guides say it’s hardy to-20F. The Christmas 2022 9 degree freeze made the leaves turn brown and fall off (zone 7b). Although it was its first winter, so not established. Not sure it will leaf out this spring. Good riddance .
Soft Caress is said to be cold hardy to zone 7b (5 °F.), but I’ve found that it is damaged in the low teens as are many narrow leaf mahonias. It is likely to survive this cold, but I’ve found its spring growth to be sparse so it never fully recovers.