Terence Lynock wrote:

Some species of Pine wikll stand temperatures down to -20C and also the
odd variety of Acer and I believe at least one of the Larch family, best
bet is look at species fromclimates you know hit -20C every year like
some of the Pines etc from the Yukon and up north around the Arctic
circle, even then it may be a few years before they are actually hardy
enough to cope with it,

regards, Terry

Great Idea. Thanks, Terry.