At least some plants can adapt to a certain extent to their conditions. As far as I know (from memory) there is no scientific evidence for whether daylilies can adapt or
If they can by how much.
The typical example of a plant adapting in one manner would be a plant growing in the middle of summer that if plunged immediately into sub-freezing conditions would die but if that same plant was grown at steadily lower temperatures and other conditions and then plunged into sub-freezing temperatures would survive those temperatures and even lower temperatures.
However, there are more basic problems. Daylilies are classified by their apparent foliage behaviour in the locations and growing conditions where they are hybridized. They are either "dormant", "semi-evergreen" or "evergreen". Unfortunately those foliage designations are not necessarily consistent and may be different in different locations and different growing conditions. Even more importantly those designations are probably almost completely unrelated to winter hardiness. How close the relationship is between foliage categories and winter hardiness can be objectively measured by their correlation. If they are strongly related the correlation would be maximal at positive or negative one. If they are totally unrelated the correlation would be minimal at zero. I have not done the necessary analysis but from my experience the relationship is probably near zero and probably of little significance.
I am in zone 4; When I purchase daylilies I pay no attention to foliage categories. In my conditions nearly all daylilies are "dormant". I expect that if those same daylilies were grown in Florida they would nearly all be "evergreen".
There are some plants that are described as not reacting well when their roots are disturbed (for example, celosias
http://aggie-horticulture.tamu...). I think some daylilies do not like to have their roots disturbed and take a long time to become properly re-established. I think those cultivars have a difficult time surviving their first winters in cold climate locations.
Last year I received an order in August. It had one fan of 'Spectral Elegance" and two fans of 'Isle of Wight'. These are siblings both evergreen and both bred in Florida from 'Ballerina on Ice' x tet 'Ruffled Masterpiece'). 'Isle of Wight' sailed through winter with no problem; 'Spectral Elegance' disappeared and made an appearance much later this spring as a tiny seedling size fan. My past experience with this type of behaviour is that 'Spectral Elegance' will sail through this coming winter with no problem and will not have any problems with future winters,
as long as I do not disturb the roots. Why do I think it is root disturbance that is the problem? I tried the experiment of simply lifting a cultivar that reacts in the same way and leaving it in exactly the same spot. It had grown undisturbed and without problems in the same location for more than six years. The very next spring it responded by producing fewer and smaller fans.
