@beckygardener
I garden in zone 9b. It is challenging, but I have over 300 registered daylilies. Mine do not clump as rapidly as they seem to do in some other zones, and they are subject to rust infestations.
In my opinion (for what it's worth), high nighttime temperatures cause the greatest climatic stress on my daylilies. Nevertheless, the evergreens and semi-evergreens seem to bounce back when temperatures moderate.
Another problem I experience is alkaline soil and water. When I can water with rainwater, everything does better!
Like you, I like Dragonfly Dawn, but it has never clumped for me. After seven or eight years, it still only has two fans. The deer have eaten it a couple of times, so that could be the reason! I really need to move it inside my deer fenced backyard.
I am convinced that my soil conditions pose a bigger issue than climatic conditions.
But we keep trying, don't we?

Maurice - Thanks for sharing some of the articles you found. I was not able to go to the link with the full article. It just circled right back to your NGA post. Not sure why that happened.

I agree too, that "eye" is probably each fan.

Brenda - Reading the effects of root knot nematodes in those articles that Maurice posted, the bad nematodes can often cause smaller increase and smaller fans. So I am sure that is why I never seem to get nice sized clumps like many on this forum.

I will say that I was surprised that the northern states have issues with these nematodes too. I honestly thought it was a southern issue because we do not have ground freezing temps in winter that might kill them, but apparently not! So this nematode issue could happen in northern states too. Interesting, to say the least!

@beckygardener

Becky, I assume by "the link to the full article" you mean the thesis. When I click on the link my screen blanks for a moment or two and the screen display returns and then a small window pops-up requiring a file name to save the thesis to my computer. Is it possible that a pop-up blocker on your computer is blocking the download of the thesis file?

You can read the thesis online without saving a copy to your computer by visiting this website
https://d.lib.msu.edu/etd/5117...

Maurice - Thank you for that link!