I have noticed that I have several cultivars of daylilies that seem to be suffering from what I consider to be "heat dormancy. Some of the plants have completely faded away, and come back as multiple small fans, others have just mostly disappeared leaving a few weak looking leaves, and are now developing new foliage.
Some of this I blamed on stress (setting seed pods, dividing, dry soil) but I am wondering if it might also be cultivar specific.
Anyone have any info on that?
All these photos were just taken, so this is what the plants look like right now.
Examples of some of my plants experiencing what I think is Heat Dormancy.




'My Path' almost totally disappeared, but now look at the new fans developing.

Example of some of my plants that did not experience Heat Dormancy

After looking at my different beds, I am almost convinced that heat dormancy is directly related to a lack of moisture. The beds with the biggest number of affected plants are far dryer than the bog bed which seems to have avoided this problem entirely except for a few of my recently acquired plants that were planted in the hot July sun with no shade. I have put shade over those and given them extra water till their roots can establish and have already seen improvement.

Larry - I think you hit the nail on the head. When I was looking at your photos, dry soil came to mind immediately.

In my daylily beds that get constant watering and even a little shade during the day, none of the seedlings have disappeared except one. (It is completely gone!) They all have various parents, so the likelihood of at least some of them going into summer dormancy should be in the 70+ seedlings, but none have, so .... water is key to a happily growing plant.

I would agree also about lack of moisture. Before our rain storm last Sunday, my daylilies were showing a lot of leaves going dormant. Since the rain they look much better. We hadn't had any rain in over 10 days and it showed.

Some of mine are doing the same. We have no rain last week or this week. May get some tomorrow. This is the longest we have been without rain this spring/summer!

I do have one daylily that by the time it is finished blooming the foliage is all down & that is FLASHER. It does it every year so seems to be in its genetics.

Claudia - Sounds like "Flasher" does go into summer dormancy regardless of water or other conditions. A true dormant of heat perhaps?

I do not even pretend to understand all this but it would appear it does.