S, uliginosa is as tough as they come.
Don't know about Amistad. It was eaten by snails long before it had to face a winter.

Amistad isn't fully hardy in Easy Yorkshire according to my friends who take cuttings and keep them in the conservatory.

Thanks Owd b and Eileen ... I think I’ll play safe, but glad I can leave S. uliginosa in situ. It was gift from the birds and new to me but very pretty 🙂

'Amistad' has come through the past two winters here in balmy Berkshire, but I take cuttings as insurance

Thanks Andrew ... I’m doing the same - it’s so worth keeping.

My Amistad didn't tolerate the Devon winter two years ago. The following year I took cuttings but slugs demolished them in my coldframe. This year I will only be putting cuttings from plants that don't attract slugs in the coldframe: Dianthus, Hebe and Erysimum. Next year I intend to buy the new salvia which is similar to Amistad but more hardy.

That’s interesting Merlin. I’d forgotten my Erysimum Jep so will now take cuttings of that too.