Delphinium Species, Larkspur

I wonder about the zone 4a rating. I grew these from robust seedlings in Buckfield, Maine (zone 4b at the time) and lost all - about a ...Read Moredozen - over the winter. But I'm trying again now that I'm in zone 5b (they are easy to grow from seed). The foliage alone is beautiful, glossy and divided, as you can see in one of the photos.

This looks very much like a species delphinium that another member of my garden club passed on to me. It has thicker leaves than most ot...Read Moreher delphiniums and seems much more resistant to snail attacks. It also self seeds and comes up in unusual spots so it persists as a perennial in that aspect. The varieties of delphinium that are derived from Delphinium elatum and D. grandiflorum are at best short-lived perennials in my garden, although I adore them for their blue flowers.