It is definitely hardy to zone 2.
You shouldn't have any problem winter-sowing them (or with any plant whose seedlings wouldn't be killed by some cool temps after germination... which won't happen here until spring) but alternatively, you could also put some in moist medium in a plastic bag in the fridge and watch for germination, or in a pot set in a cold room or cellar. If you do one of the last two methods, you will have to provide light indoors after germination in order to keep the seedlings healthy, unless you wait until say Feb-March before sowing (in which case, the time indoors will be shorter and light quality will be less important).
I find several seedlings under my plant every year (and have been pulling them out). The seeds don't appear to be eaten by birds or animals particularly here. According to Deno, water washing with soap is effective at removing the oily material from the seed. Anecdotally, someone out there probably likes using cider for seed germination, but why a very weak acid would be more effective at breaking up oil than a soap is very mysterious... don't think there's any chemical basis for it.
