I would agree that planting daylily seedlings every six inches should be okay.
That can be checked.
The figure shows an example layout.
After the seedlings have been chosen that are going to be saved for evaluation (or chosen for introduction) etc. as long as their positions on a map of the seedling bed are collected then a check can be made as to whether there was too much competition and it strongly affected the characteristics of the seedlings. That assumes that seedlings are selected for more than flower colour - that they are also selected for characteristics such as scape heights, bud counts, fan increase rates, fan sizes, etc.
The test is reasonably simple (and can be made so that its statistical significance could be checked). Count the number of seedlings in the very outer most sections of the bed. As an example, in the case of the diagram there are 22 seedlings in total in the outer section. There are 18 seedlings in total in the inner section. The percentage (or proportion) of seedlings that are selected should be the approximately the same in both sections
not the numbers. If a significantly larger percentage/proportion of seedlings are selected from the outer section then that would suggest that there is significantly less competition in that section than in the inner section and the spacing should be increased in the inner sections.
One assumption is that when the seedlings are first planted they are not planted in specific locations according to their sizes - in other words, they are planted at random with respect to their position in the bed. For example, planting the larger seedlings in the inner sections or the outer sections or vice versa or in any pattern would make the comparison test useless.
