Ask Mr. Smarty Plants

We did find the Previous Mr. Smarty Plants answer which asked about the Cahaba Lily, which will bring you up to speed on that. Since we are not a forum, we can't guarantee original visitor will ever see your comment, but will leave it in so she will get the information if she searches Mr. Smarty Plants.

Now, on to your question about the difference between Asiatic lily and daylillies. This article from the American Hemerocallis Society has a database on which you could search for information. The daylilies are all now part of the genus Hemerocallis, none of which are native to North America, but rather to Eurasia, including China, Korea, and Japan.

There are members of the Liliaceae family which are native to North America, but the name "Asiatic" is a clue that native lilies are not what you are talking about. Try this website from the North American Lily Society to see if you can get any help there.

Native North American lilies belong to the genus Hymenocallis, in the family Liliaceae. Searching on Hymenocallis we found 6 members of the species, which includes Hymenocallis liriosme (Spider lily). Searching on Lialiaceae there were 268 members of that family listed. So, when you ask us how you can tell what kind of lily you have, frankly, we don't know. We suggest, again, that you look at the two societies listed above and see if they can help you. 

The Lady Bird Johnson Wildflower Center deals only with plants native not only to North America but to the areas in which they are being grown.