http://www.localharvest.org/store/item.jsp?id=2732

Let's see if that works...

"Nannorrhops ritchieana"

Hardy to 24 degrees ... while that is below freezing, it's not the same as -20F.

That site specifies "USDA Zones 6b to 11. (Use of mulch or potted plant moved indoors will allow this palm to be grown in zones as low as 2b." Which is not the same as having it growing outside in Western Montana ...

The Mazari palm native to Iran comes from a region where rainfall is scarce, I mean real scarce. It's reported hardiness varies from upper-teens in wet winter climates to -20F in dry high desert climates that have the freak occurance of temperatures that low, but with average temperatures in the winter of highs in the low 50's and lows around 15F.
Don't be fooled by the zone scam. Zones only tell one factor and ignore the more important factors.

We often hear about hardy palm, but I never hear about that one, I was just wondering if anyone have tried that one! In my case, 5b Canadian, I can only hope for poted palm and entering them in the garage during winter time. The only thing about poting palm is that they don't grow as fast as in the ground.

Cheers

Nannorrhops ritchieana is trunkless palm (or trunk below the soil), not commonly what people want for tropical look.

It will fry in the winter in both places. I won't even try it here in Virginia in Zone 7 because of the wet winter.

Maybe they have a european source that told them -20C and they messed up and didnt convert it.