Perennial " annuals"

[Sr Clare Julian]

I am finding in this sheltered mountain place that more and more of the flowering plants we think of as annuals are perennials, only killed off by harsh weather. Marigolds (calendula) live and flower for many years, and this year the nasturtium vines against the front wall are trying to flower; as are snapdragons now. We have had hard frost, but there is shelter too..Is this common?