needrain said: There still could be a genetic component to rebloom. I would suspect a dosage effect at play in the trait.
I would agree, as long as there were daylily species that did not have the genetic ability to rebloom in the original mix from which modern cultivars have been derived. My search of the information available for those original plants suggests that probably all the species used had the genetic ability to rebloom.
What may vary is the time between rebloom scapes on the same single fan crown. That may depend on the size of the flowers, the number of buds, the height of the scape related to the number of leaves (their length and width), etc. In other words, how much resource is required for the rebloom and the capability to produce the necessary amount of resource. Water, nitrogen, fertilizer, lack of competition from weeds and reduced competition from other fans of the same cultivar (reduced self-competition) all may have an effect.
