I do not check registered foliage on the daylilies I buy so I grow many evergreens in zone 4 and they are nearly all dormant during our winter, that is they lose their leaves and form a bud. Their foliage does not survive winter here.
Of the many hundreds of registered cultivars that I grow there may be two diploid registered evergreens that act as evergreens and may not form a bud during our winters. Their leaves are killed back down to about 2 or 3 inches from the soil surface by the winter cold. I have been growing them for at least 12 years and they are both single tiny fans about 1/8" wide. Any increase they may make during a growing season usually is completely killed by winter.
Yesterday and today I have been reading about seedlings of other perennials that may not survive their first winters because they are apparently too small to have developed an overwintering bud. If these two cultivars survive the coming winter I will try to force their growth with fertilizer next year to try to make them larger and see if that helps them survive future winters.
Another registered evergreen diploid that I have seen bloom only once here in about 10 years I have managed to increase to three decent size fans and one small fan this year. Sadly none of the fans bloomed. I hope that it survives this coming winter better than it has in the past and that I may see bloom next year.
I don't have a list of all the cultivars that I grow but perhaps I may make one as a winter project and check to see how many evergreens I grow that act as normal dormants. At the moment there appear to be three out of probably about 800 registered cultivars (of all foliage types) that are registered as evergreen and may act as evergreen here.
