I can confirm Jim's statement on this taxon in that its winter state is complete dormancy of all foliage, it just withers and beds down for the winter. The effect of having living tissue exposed during winter would result in severe desiccation. It also seems to be the case with many Iris, as with Lilium that wild seed origin is often important to ensure survival. There are a few taxa here from both genera which form clines - north to south, low to high altitude, east to west with variable degrees of success and failure. Our main seed provenance of Lilium nepalense appears not to have read the extant literature as to frost hardiness having several times dealt with -20 C to - 25 C. Just try whatever you feel might work if it seems interesting, all you loose is your time and the price of the seed but now and again there is the odd bonus.