I use pots. I always start out with the crown very close to the top of the soil line. If I notice one pot not blooming, I can about bet I've planted the daylily too deep and the crown is way down in the pot. I always do the little "hill" in the center of my pot to set the bottom of the crown on but sometimes, my "hill" isn't tall enough and I don't notice. This in turn will sink down into the pot as the soil settles, putting the crown down into the pot deeper. I've lost maybe 5 plants to crown rot in my 10 years of growing daylilies in pots and all have been planted too deep. With our weather from 10 below up to 110 above, we get a wide variety of conditions. But, nothing compared to the northern part of this country.
I'm like most above, if in 20 years you haven't had alot of trouble, I wouldn't worry about it. When you get in a new plant, I'd probably start it out a little(little being maybe an inch) above grade, because in most cases, it will sink down some. Especially in the summer and I wouldn't put summertime mulch over the crown. This can lead to rot when you get really high temps like ya'll have had this year. Then, I would pull the mulch up over the crown for winter.(This is what I would do, what's good for you may be totally different) I just read what Juli had posted about region, and I agree totally.
