I just started doing daylilies in the last couple of years, Mary Ann, but I would suspect that the thinning out is definitely affecting the blooms. Also, are you giving them any kind of fertilizer or compost? I do know that maximum sun provides maximum bloom. I am no expert, but I'd let the clumps go for a couple of years and see how they do. In my yard now the smaller divisions are only sending up one or two scapes, while my thicker ones have easily a half dozen or more. Most don't even have scapes at all yet, I think the screwy weather is making them cranky so I'm just trying to be patient!
Good luck, which varities do you have?
Amy

When you say thinning, do you mean you're dividing your clumps by digging up part of them and transplanting them? I'd think that only needs to happen every two or three years. Mine are flowering pretty well right now in zone 6 (Utah Valley), but they get a full day's sun. I don't divide mine very often. Did it once in the past four years. A few are not doing well because they weren't getting enough water, since other plants grew up in front of the sprinkler, but I fixed that last week, and things should rebound now.

I just remembered that I had posted questions here. Thanks for answering. I have daylilies in several spots- the ones that get the most shade have bloomed well. One clump that is 3x3 feet of solid plants has just one scape, and gets sun most of the day. My question is should I break up a clump and put each single bulb with its leaves in a spot a few feet away from other dl? In the past, I have left a few inches between and the next yr they are all crowded together again.

Okay, so I have no direct experience in dividing day lilies, however, I intend to gain some when mine quit blooming this summer. But I have divided other plants including iris, which must be somewhat comparable. Probably, the best information would come from the more extensive instructions on line provided by the USDA or other sources. Just google "dividing day lilies" and you'll see several choices along with pictures. But, in general, what provides renewed blooming is dividing the the original clump through the center. This spurs new growth where previously growth had slowed or ended. So the idea is to split the large original clump into two or three smaller clumps with a spading fork leaving one clump in the original place and then placing the other clump or clumps at a new location or locations several feet away or more so the two clumps do not grow together. If you have been breaking off single bulbs from the outside edge and replanting them a few inches away from the original plant, it is possible that you've been doing minor surgery where an amputation was indicated, and that is why you have few blooms. I hope I understood what you were asking, but if I did not, try again. There are some people who post on this site who really know about day lilies. They can tell you much more than I can.

THANK YOU, DEE, FOR THE EXPLANATION. I THINK I HAVE BEEN DIVIDING INCORRECTLY! I WILL DO THE GOOGLE SEARCH TOO....MARY ANN

Mary Ann, you're not dividing incorrectly, I think you're just dividing too frequently. The daylily forum on this site is excellent and everyone is very friendly - might try there!
Amy

I have a confession to make. Now all of the lilies I thought were not going to bloom HAVE bloomed. I was too impatient. Even in this unusual hot weather, there are new blooms everyday. I will try to remember all this next yr and not panic! Thanks to all, mary ann

There are many reasons for daylilies not blooming. Not enough sun,planted too deep, crowded and needs dividing,etc. Sometimes they won't bloom the first year after they're planted. I wouldn't even want to guess without seeing the plants.

Dividing daylilies is very simple. Lift the entire clump, knock the soil off, hose it off if you wish. Some cultivars are easier to divide than others. I have had some where the divisions just fall apart, others can just be wiggled apart, some may need to be cut with a knife, and then there are a few that require high explosives.

Someone compared dividing iris with dividing daylilies. Not the same. An Iris rhizome, once it blooms will never bloom again. A daylily division will bloom again. I had a part time garden employee who told me she knew how to divide iris. She replanted the mules (already bloomed) and discarded the good rhizomes. It was too late by the time I discovered what she'd done.

Something I forgot to mention is that daylilies are not at their best until about the 3rd season after planting in this climate, particularly the tetraploids. If I have one that sulks for 2 years and doesn't bloom, I'll move it. That usually does the trick.

Don't forget that daylilies love water. They are very drought tolerant, but they are not xeric plants. To have the best bloom and great plants, give them lots of water. As long as you have adequate drainage, you really can't over water them.

The American Hemerocallis Society has a website where you can learn more about daylilies than you ever wanted to know.

Good luck with your daylilies. I'm hopelessly addicted to them. My collection numbers more than 4,000. I've gotten more pleasure from daylilies than any other plant I've ever grown.

Karen
The Cat Lady's Garden
AHS Display Garden
Aurora, CO

Here is a link that might be useful: AHS