You can buy daylilies with known ploidy at various places, specialist growers, garden centres, etc. The label may not show the ploidy though, you would need to look up its name in the database here (click on Plant Database top left of this page) or else in the American Hemerocallis Society's registration database here and normally the ploidy for that daylily will be shown:
http://www.daylilies.org/Dayli...
You may be able to find out some local sources via this page for your AHS region:
http://www.daylilies.org/AHSre...
Cross-posted with DND, sorry.
