From the article,
"However I hybridized a daylily that flowers for 1 week and more. The cooler the weather, the longer this hybrid flowers."
I think there may be some confusion (if there was translation). Both these sentences apply to the length of the flowering season.
In cool weather a daylily flower may remain open with acceptable appearance for two days. I have very strong doubts that a daylily has been selected that remains open for seven days (and more) with acceptable appearance. To do so would typically mean that hundreds of crosses were made and seedlings flowered. The length of time that the flowers of those hundreds of those seedlings remained open would be measured and averaged. Then a small number of those seedlings with the longest lasting flowers would be crossed together and hundreds of seedlings produced for the next generation. The process would be repeated. After enough generations the length of time that a flower remained open in the selected line would be substantially longer than one day. Under cooler temperatures it would probably be longer than two days. I doubt that a daylily with longer lasting flowers has been produced by selection; if it was it would not be a single daylily but an entire selection line of daylilies.
The only other way to get genetically longer lasting daylily flowers would be to have incredible luck and find a dominant mutation that allowed the flowers to last longer than a day. Most mutations are recessive and since diploid daylilies (where it would be easiest to find new mutations) tend to be self-incompatible and suffer from high inbreeding depression I doubt that anyone has found a recessive mutation for long living daylily flowers. Typically the odds of finding a dominant mutation versus a recessive mutation are about 20 to 1. I doubt that anyone has found a dominant mutation for flowers that live one week or longer.
