I am going to jump in here about dormancy.
There are basically three types of dormancy. I will describe each kind in general and then give them their scientific names.
The sort of dormancy that many gardeners are familiar with is that there can be many buds on the stem of a plant but they do not grow/sprout. They stay "dormant" until the tip of the stem is pinched-off. Some may recognize that as being apical dominance. This is paradormancy.
The next sort of dormancy is when the temperatures are too cold, or too hot, or there is not enough water and the plant stops growing. The plant is just resting and when the temperatures are warmer or the rainy season starts the plant grows again. This is ecodormancy.
The third sort of dormancy is very much like the second but the plant will not start to grow again until it experiences something specific. The usual example of this is fruit trees or small fruit plants that stop growing for winter. They will not start to grow again until after they experience a certain amount of cold, even if the temperatures are warm enough (chilling degrees). They use that amount of cold as a signal that winter is over (so they do not start to grow before winter is over, because of a warm spell that is then followed by killing cold temperatures). This is endodormancy.
Daylilies have been classified as dormant, evergreen and semi-evergreen. Those classifications are not based on the different types of dormancy. An 'evergreen' daylily is or should be a daylily that does not go dormant, that is, it is evergrowing or non-dormant. A dormant daylily could be either ecodormant or endodormant or it could be both at different times of the year and under different conditions.
If we look at the way a fan grows we see a pattern of leaves. We could think of the leaves on one side as being 'left' leaves and the leaves on the other side as being 'right' leaves. For example, < < < < > > > > where < and > are single leaves of a fan (it may help to visualize the fan by thinking of it as having been cut back and then we look down on it from the top). When a fan goes dormant it stops producing new leaves. The leaves it grew before going dormant will stay alive for quite a long time (depending on growing conditions).
Daylilies can be paradormant. The best example of this happens in some daylily cultivars when they bloom. If we look at the leaves on a daylily fan when it has flowers blooming on its scape we can see two different patterns. In one pattern the scape is more or less centred in the fan with leaves on both sides but only left leaves on the left side and only right leaves on the right side, for example < < < 0 > > > where 0 is the scape. The fan stopped growing new leaves when the scape appeared. That fan is paradormant or 'dormant' (at least for a time). We know that it is paradormant if it starts to grow within a reasonable amount of time after we cut off the leaves and scape.
In the other pattern the fan does not stop growing new leaves when the scape appears and in this pattern the scape is off-centre with both left and right leaves on one side of the fan and just one sort of leaf on the other side. For example, < < < < < < > > 0 > > > > or < < < < 0 < < > > > > Those fans are not dormant; they are evergrowing.
When winter comes some daylilies stop growing (I mean they stop producing new leaves). Those daylilies are 'dormant'. They could be ecodormant or they could be endodormant or if they are like some other perennials they could be endodormant shortly before winter and ecodormant during the dead of winter. Stout presented evidence that suggested that a few of the daylilies of that time were endodormant - to grow properly again after they had become dormant (stopped growing in the warmth of a greenhouse) they had to experience a certain amount of cold.
There is a relatively easy test for whether a plant is ecodormant or endodormant on a certain date. Take the plant from the cold outside and bring it inside to the warmth and give it enough light, water, etc. If the plant starts to grow within a reasonable amount of time (many researchers use a couple of weeks) then the plant was ecodormant. If it does not grow in that time then it was endodormant.
I have tried this with several daylily cultivars, including some older ones from Stout's time and for several different dates. All the daylilies so far have been ecodormant. When a plant is ecodormant it does not really matter whether it was temperature or light (quantity or length - photoperiod) that caused the dormancy - basically the growing conditions were not good enough for the plant to grow and so it went dormant until the growing conditions become good again. Daylilies that are ecodormant should be able to grow well anywhere, including the tropics and where there is little or no cold during winter. Daylilies that are endodormant may not grow well if they do not receive enough cold to signal that winter is over. Stout did however find that some apparently endodormant daylilies could grow past their problems but that others died.
A few years ago, there was an article in the Daylily Journal about growing daylilies from seed to flowering in a greenhouse, "Daylily culture using hydroponics" by George Doorakian, volume 55 pages 406-416, 2000. He grew daylilies from seed from August to May in a greenhouse in Massuchusetts with just natural light at temperatures that only varied from 70 to 80F. He grew diploids and tetraploids, dormants and evergreens in hydroponics and normal pots. The plants bloomed when they were from 6 to 14 months old with the dormants being the ones that took longer and the plants in pots also took longer. They did not require cold. Researchers have also verified that the majority of daylies do not require cold (that is, none did that were tested).
Daylilies have been grown and hybridized for a long time after Stout's test. A very large proportion of all modern daylily cutlivars were hybridized in warm winter climates where dormancy will have been selected against. There are probably very very few modern endodormant daylily cultivars (The ones that would not be expected to grow well in warm winter climates because of their endodormancy). I have not found one yet, even in older cultivars.
If you can help by providing names of daylilies that are possible candidates because they dwindled away in a garden with mild winters please let me know their names.
