You can find answers to your questions by searching the Web. Search on "daylily ploidy" and "daylily hardiness" or just "daylily" There is tons of info out there. As for hardiness, daylilies as a class are VERY hardy. It's not so much will they grow, but when will they bloom.

Here's another suggestion: Open another thread with the subject "Best choices for zones 4/5". I'll wager you will get a zillion responses.

Where are you located? Are there any daylily clubs nearby? Are you familiar with the American Hemerocallis Society?

I will try to give you the short course. Diploid daylilies are the original type. They have two sets of chromosomes. I am not sure who did it or how it happened, but a way was found to double that number of chromosomes. Those are tetraploid daylilies. Both are valuable and have their pros and cons (and advocates and detractors). We mostly grow tets but not because we have anything against dips. We just found that the features we like best in daylilies (especially teeth) are more commonly found in tets. One is not better than the other. In fact, I think there is a resurgence of interest in the diploids, mainly because of patterns and unusual forms and spiders.

As far as hardiness is concerned, that is a hotly debated topic. Conventional wisdom says that there are three types of daylilies--dormant, semi-evergreen and evergreen. The evergreen types grow well in the south, but you may find an evergreen that grows well in your zone. Dormants are what northern growers prize, but some say that dormants can be tender.

Zone may not have as much to do with hardiness as other factors. For example, we are zone 6b, but some people north of us can grow some daylilies we cannot. The difference may be winter snow cover. If you have winter snow cover, that acts as a blanket and keeps the temperatures more constant. The daylilies like this. We, however, usually don't have much snow cover, and with these mild winters, have had many fluctuations in temperatures. That leads to freeze and thaw cycles, which the daylilies are not so fond of.

In choosing daylilies, it's best when starting out to find some nurseries that offer field grown daylilies in a climate similar to yours. That way you would know that they are able to increase those daylilies enough for sale. A daylily that is just hanging on (because it's too tender) doesn't usually increase very well.

I hope that helps somewhat. And welcome to this wonderful obsession we call daylily growing.

Nancy

Thanks Nancy you were very helpful.