I have a few things on my lists here, but never got around to putting them all in. I seldom trade since its almost impossible for me to use a shovel, and I depend on a couple of my friends to do any digging for me. I hate to ask them, so... I used to do a lot of selling and some trading years ago. Now, most of my plants are older, and not in much demand as they were years ago.
I had a fair amount of daylilies at one time, when I had a side business here of selling and also hybridized. I had about 800 named cultivars at one time, and a few thousand seedlings. As my mobility issues increased, I had to decrease the garden area. I also had a whole hillside of perennials and shrubs.
It was very hard for me to choose what to keep. I got rid of more and more each year, till I am down to maybe 25 favorite seedlings and 75-100 named ones. All are in two small beds, and are planted in rows, with a few out in the small remaining perennial bed. Once a month or so, I hire a local woman to come and weed and help keep perennials dead headed and cut back.
I tried to keep a variety. Tall, short, small, big, spiders, etc. One thing I did keep more of than anything else were pure saturated selfs without eyes, watermarks, teeth, edges. I like daylilies without all the "bling" and they are getting harder to find.
I kept plants that were really good performers - but for me - I kept ones that didn't multiply quickly. Some do - like Nutmeg Elf - but others don't. If I see one fan increase every other year, that's good for me in my situation. I don't irrigate, and don't fertilize very often, so they are not all pumped up to grow lots of new fans. Since it is such a problem for me to have someone here to dig them and divide them, the less that needs done, the better for me. Just because a daylily does not increase like a rabbit, does not mean it does not perform well. At least not in my opinion. Yet, many of the daylilies that I kept that don't increase much here, when planted in a friend's garden who really has great soil, irrigates, and fertilizes - they increase much faster for her.
For my seedlings - I tried to keep the ones that were different. They needed to have something unusual about them. Not always "pretty" but something different. A unique color, an odd shape, etc.
I also looked at health - I didn't keep any that always had ratty looking foliage (leaf streak - I have not had rust here since 2001 even though I don't spray).
Yellow daylilies are my favorites because they look good at 6 a.m, 2 p.m. and 8 p.m. no matter if it has rained, or full sun, or shade. They also mix well with all colors of perennials. I imagine 1/3 of what I kept are yellow, another 1/3 are peach, pink, orange. The last 1/3 are purple and red. I think I only have two or three that have eyes or patterns.