I do not consider that daylilies are "xeric" plants.
Some of the natural species tend to be associated with moors, bogs, etc. in their natural locations (for example, Hemerocallis dumortierii complex, H. dumortieri var. esculenta). Others may be associated with drier but coastal areas, for example H. fulva var littorea.
Every summer I put many potted daylilies into our pond. Sometimes, after heavy rains the pond level rises to above the pot rim. I have not lost a daylily yet. They seem to do quite well under those conditions and flower without any further attention on my part. I have been doing this for more than fifteen years to the same potted cultivars.
A couple of researchers have checked plant species for the effects of submersion under water for various lengths of time. One study compared ten species of plants with high adaptability to aquatic environments. Daylilies scored the highest for flooding tolerance as measured by plant height and leaf width. That strongly suggests that daylilies are adapted to moist/wet environments rather than xeric (dry) environments.
