I am wondering if a dormant daylily can pollinate a semi evergreen daylily, as long as they are both diploids or Tetraploids? I am just getting started in breeding daylilies, and wonder if they can be cross pollinated. If they can, would their seeds produce sterile daylilies?

Yes, a dormant daylily can pollinate an evergreen daylily and the seeds will not be sterile as long as tetraploids are crossed with tetraploids and diploids are crossed with diploids.

Alicia in addition to Robin's comments, I am not sure if you are aware that some plants are sterile. Always check before you buy.

Not to detour this thread, but is that a common thing? Sterile daylilies?

I've seen daylilies that were pod-sterile, or pollen-sterile, but other than, for example, ditch lilies, are there that many that are completely sterile?

I'm not a hybridizer, so this is new to me. I'm interested to know.