I love this subject! I should say that I don't have a scientific bone in my body, but I am a long time gardener and I hope I have my terms correct.... maybe. This topic coincides with another that cost me a friendship, so I need to tread carefully here.
From what I understand in dummy language, summer dormancy differs from stress related inactivity. Some of my more evergreen plants slow to a crawl when it is extremely hot and dry, but they continue growing new leaves, even slowly. My "summer dormant" plants begin to go down as they are done blooming and will only grow a couple small leaves that will turn yellow at the first sign of frost. Anyone growing Neon Flamingo or Heavenly Angel Ice will observe similar behavior. (I hope) I suppose that might differ if you don't have winters.
This first photo is showing what I call "summer dormancy". This plant has several clumps that all do the same thing year after year regardless of the weather. It will grow a few leaves later on, but they will never get very big. This type of daylily is especially nice in mixed plantings with annuals that take up the slack when the daylilies are done. These plants, at least for me, are very winter hardy and generally have strappy leaves. They normally don't rebloom either. I call them "hard dormants" although I am not certain that is the correct term. Some people insist that the correct term is "deciduous". Yeah, well, whatever...
This second photo shows a more evergreen plant right next door in an adjacent row that is fully green and comes from more evergreen stock plants. This kind of plant might look really bad in heavy stress conditions, and might even lose most of the outer leaves, but it will continue to grow as conditions improve- all the way to winter, and even after several very hard freezes. This type of plant has the ability to look really nice all summer if given the right conditions, and many of them can rebloom. Not all though!
So, if I have it right, "summer stress" is totally different than "summer dormant". At least for me, that is what I observe in my garden.
