We have daylilies in the raised beds mostly but we do have daylilies in pots. These are the ones we sell mainly, but I have snagged quite a few of them and put them out in the hybridizing area to use and left them in pots. Also any that I didn't sell just stay in the pots.
I use the same mixture of pine bark (dime size) and 10% sand that I use in the beds. I just pour sand on a pile of mulch (on the table) and mix all together by hand so it's not an exact 10%; I just eyeball it. I use different size pots, 1 gal, 2 gal, 3 gal, and 5 gal. The 1 gal for seedlings and daylilies that won't be in the pot that long, the 2 and 3 gal for the ones I divided with very large roots, and the 5 gal for larger clumps that I don't have a place for or for the ones I'm growing that I donated to the club, and then the club auction plants.
I fill the pots about 2/3 full with the pine bark/sand mixture then add chicken litter (the dry, already processed kind) and alfalfa pellets then mix in with the soil. I kind of make a mound in the middle the best I can and put the daylily in and backfill a little. I then add the slow release fertilzer, more alfalfa pellets, more chicken litter, a little ironite or epsom salt (whichever I have available at the time) and a pinch of 8-8-8 or 6-6-6 quick release fertilzer (it's pretty much lawn fertilzer and only last I think 30 days maybe less). I don't always use the quick release, but I have been this year because it's here. Then I cover all of that up with the rest of the pine bark. I used to just add all the above and mix in before putting the daylily in the pot but I figured more would make it to the roots if it was above the roots. I also used to just top dress the pot with the extra ingredients but when you pick up one pot in each hand the fertilzer and stuff rolls to one side or falls out of the pot since it leans at an angle when picked up.
I basically treat the potted ones the same as the planted ones except I top dress with alfalfa pellets only 2 times in a year instead of 3-4 for the beds since the foliage gets in the way and it's very back breaking trying to add stuff to the pots. The ones I plant in the beds I add the milorganite into the holes where the pots I will go back and top dress with it. I also fertilize with water soluble (miracle-gro, peters, etc) fertilzer on a regular basis. Lately we have been using Daniels Plant Food, which is 10-4-3 and not the normal ratio we would use, but the daylilies seem to love it and it feeds the soil microbes as well as the plant. We rotate the Miracle-Gro and the Daniels.
Benefits: It's easy to move plants where you need them if hybridizing (and need shade) or if maybe want to get a feel for how things will look in the garden once everything blooms and can move them around to get the look you want.. You can move them when you need to spray weed killer instead of worrying about trying not to spray the plants. Easier to move when needing dividing (unless in a really big pot) instead of having to dig it up.
Disadvantages: Depending on what type of pots you use (especially the black nursery pots) they dry out a lot faster than if in the ground. Also, once the foiliage is fully grown out and covers the pot, if you aren't careful or water long enough, the water will roll off the foliage onto the ground and not in the pot. If hand watering it's best to make 2 rounds with the water because if the mulch/soil is really dry the water just runs down the side and out the holes in the bottom of the pots. It's best to moisten the top layer of soil and then come back and water deeper.
I have also found that if you have A LOT of pots and they are really bunched up together that sometimes the plants get leggy trying to compete with each other for the sun. They will grow just fine in pots (there are a few people here who only grow in pots) as long as they get adequate water. They grow even better if the pots are sitting in/on something that the feeder roots can grow down to to get more moisture. I sit my pots in the raised beds with mulch in them and sometimes when I go to move a pot there is 2 feet of feeder roots growing into the mulch below the pots.
IMHO, they do grow better planted in a bed/ground and spread out better. There's no way that some of my clumps would be as big as they are if they had been planted in a pot. But of course that depends on your soil too. If you have yucky, mucky, thick, dense clay that doesn't drain then they may not fair as well or if there are tree roots sucking up all the nutrients and water (like crepe myrtles do) and so on.
