When I search the daylily forum for central and lateral scapes I find only this thread; could you please indicate the thread you found.
Biologically there is no real difference between a scape that appears in the centre of the fan and one that appears laterally.
Each daylily fan has a growing point in the centre. The growing point produces the leaves; first one leaf on the 'left' side and then the next leaf on the 'right' side and then continuing by producing the next leaf on the 'left' side and so on. When the fan is large enough or old enough the growing point stops producing new leaves and produces a scape. That growing point gets destroyed or all used up when it produces the scape. Most plants are able to produce new growing points (buds) in the space between each leaf and the stem. In daylilies the stem is the crown and daylilies can produce new growing points in those locations. The fan that has produced a scape then produces a new growing point or bud either on the left side or the right side of the scape (or sometimes on both sides at the same time).
The new growing points (or the replacement fans) will produce their own new leaves until they are large enough or old enough to produce their scapes.
After the growing point switches from making leaves to making the scape it takes time to make all the necessary changes inside the growing point to make the scape. During that time, which may be quite a long time, the new growing points (fans) are also developing. Depending on growing conditions and environmental factors the scape may not appear until after a new replacement fan appears. The scape will then be a lateral scape.
Some daylily growers may believe that instead of the central growing point becoming the scape, a lateral, axillary bud or growing point may sometimes become a scape immediately instead of producing new leaves first. As far as I know that is not considered to be the way that scapes develop in daylilies.
Some daylily growers may believe that lateral scapes, especially if they seem to appear outside of all fan leaves and early in the growing season, are 'leftover' rebloom scapes from the previous growing season/year.
Researchers have examined what causes daylilies to flower and have not found that they respond to special temperatures (cold) or day-lengths. Daylilies seem to be perennials that flower much the same way that petunias and tomatoes do. Both petunias and tomatoes are perennials. They each produce a certain number of leaves and then flower and then produce a certain number of leaves and then flower and do that over and over again. So in reality, all or most daylily scapes could be described as being left-over from the previous year or growing season depending on whether the new fans in that year became large enough to change over from producing leaves to producing the scape before the previous growing season ended. All scapes after the very first one on a fan could be described as rebloom scapes or perhaps even all daylilies have the ability to rebloom in the right growing conditions.
