needrain said:" Is this dormancy of a sort? Meaning the plant as a whole?
Yes, this is dormancy. For some cultivars, growing in certain conditions, it is the only dormancy. For example, in my usual growing conditions, 'Heavenly Harmony' produces its scape in early June and does not make a single new leaf from then until September. 'Ophir' produces its scape in early June and usually does not make a single new leaf until the next year in the spring.
Do fans on the same daylily without scapes also quit making new leaves?
Sometimes they also stop and sometimes they do not stop but continue to make new leaves. Sometimes it is the smaller, juvenile or immature fans that continue to make new leaves.
I wondered last year if it was due to the excessive heat and if it might be a sign of the plants weakening. However, sometime after bloom but well before the heat was gone, most of the plants were clearly growing actively again.
Some growers call that "summer dormancy". However, "summer dormancy" and "winter dormancy" may be the same thing. Often when a cultivar is described as being summer dormant it is because it was dormant around the time of flowering (not making new leaves) but also because the old crop of leaves yellowed and died in the heat of the summer. When the old crop of leaves does not yellow during the heat of the summer but continues to be green until later in the year growers may not notice that the daylily is not making new leaves (and is dormant).
I'm going to watch this one a bit more closely this year. There seemed to be a definite rest period toward the end of blooming and then a resumption of active growth. I'm not sure it wasn't heat related or tied to another cause though, because that rest period also seemed to be occurring in the plants that did not bloom. It's possible those formed scapes that simply aborted and were still on the same schedule as those with successful scapes.
It is possible that the fans that did not bloom had aborted their scapes, but it is also possible that both sorts of fans take a rest at the same time because that is when they have made all the new leaves in that crop.
You might want to watch when the fans take a rest in making new leaves, when the old crop of leaves starts to noticeably yellow and when(if) they die and when the fans start to make new leaves again. In one of my tests of 'Ophir' I took some fans that had stopped producing new leaves and removed all their old leaves. On a second group I removed their scapes and on a third group I removed both their scapes and all their leaves. One group was left alone. The groups that had their old crop of leaves removed sprouted new leaves. On your plants that took a rest toward the end of blooming, heat
may have caused the crop of leaves to start to age and decline (yellow). That
may have released the fans from dormancy so they then sprouted a new crop of leaves.
In general plants are very flexible in how they grow and daylilies are quite normal in that respect. Young, small, immature or juvenile fans
may grow as many leaves as they can in a season while older larger mature or adult fans
may only grow a set number (more or less) of leaves before producing a scape. We do not know enough details about how different daylily cultivars grow.
