I don't know if you have seen this Hostas for warm climates

The only ones with montana heritage I noted were Stingray & Ebb Tide. Hope this helps.

What exactly do you mean by "higher" zones? Since the USDA zone system was created ONLY to measure winter cold tolerance, you will need some other guideline to evaluate suitability in hot climates. In my zone 9, you can grow any kind of hosta you want. They all thrive if you can keep the deer, slugs and snails away!!

I mean the hotter places. I'm in the DFW area, so it gets really hot. I generally have enough cold to keep them happy. It's the heat that seems to stress them.

bkay