@gleni
Part of the problem is that whether a plant is registered as a "dormant" does not provide any information about whether the plant is able to grow well at high temperatures and locations with high temperatures during the growing season tend to not have low temperatures during their "winters". Of the two possible problems the winters cannot simply be assumed to be the problem.
Plant growth and development depends on a number of factors but an important one is temperature. All plants have three important temperatures for their growth and development. These are called their cardinal temperatures. There is a base temperature below which no growth occurs. For some daylilies that may be about 2 C for others it may be between 6 C and 8 C. Then there is their optimum temperature. Arisumi indicated that was near to 72 F (about 22 C) for the cultivar he examined. Lastly there is a maximum temperature above which there is no growth. Temperatures above the maximum are likely to be detrimental to the health of the plant.
Many ornamental plants have maximum temperatures about 31 C or close to 88 F.
If a daylily registered as "dormant" was hybridized in a location that did not experience high temperatures regularly and from parents that were also hybridized in locations that did not experience high temperatures regularly then it is unlikely to do well in a location that regularly has high temperatures. Such daylilies may well be registered as "dormant" but it is not whether they are dormant or not that may affect their growth, flowering and survival in locations that do not have cold winters. It may be that those same locations have high temperatures throughout the growing season that detrimentally affect the growth and flowering of the plant.
Note the daylily Arisumi examined flowered very poorly at 85 F and not at all at 95 F. It grew poorly at both temperatures.
Specifically 'Glorious Autumn' was hybridized by Kirchhoff in Florida and even though registered as a "dormant" should grow well in Florida type temperatures and weather. Its parent 'Carrot Rouge Truffle' is also likely to be have been hybridized in Florida (registered by Schwarz-Kirchhoff) and although registered as a "dormant" should also grow well in Florida type temperatures and weather. I would look for something other than the "dormant" designation for why it may not have grown well for you, since it presumably grew well for Daylily World in Florida, well enough to be introduced.
