Thank you all and especially Fred for answering my questions and providing very useful important information.
I have brought a number of daylilies inside to grow during the winter to see what dormancy in daylilies really is.
Biologists have studied dormancy most in trees. Much of what is known about dormancy is about plants that make buds for the winter and have those buds in the air. Plants that grow near the ground like daylilies can also make buds but often those buds are protected by the soil and old dead leaves, etc. So the behaviour of a dormant daylily may not be the same as the behaviour of a dormant tree that has its buds in the typically much colder air.
A daylily fan grows its leaves (and scape) from a special location in the centre of the fan. That location produces all the leaves, like an assembly line with the leaves starting out as tiny microscopic babies and getting larger and larger in sequence as they grow. The location is the growing point or technically the shoot apical meristem (SAM).
To biologists dormant means not visibly growing but it is used only for those parts of a plant that have meristems like the SAM. When the SAM is not dormant it produces new leaves. When it is dormant it stops producing new leaves. The leaves can grow or they can not grow but that does not change whether the SAM is dormant or not dormant. That is, once the leaf has been produced its behaviour is independent of the SAM's behaviour.
Leaves grow from tiny baby leaves to mature long leaves and they live for quite some time (in evergreen trees a leaf might live as long as or longer than ten years). After a leaf has been adult or mature size for some time it will die (lets say of old age). It will yellow and dry up. If the daylily does not get enough water or if the weather is too cold then the leaves can die. Whether the leaves die or do not die or when they die does not affect whether the SAM is dormant or not dormant.
Plants are not warm-blooded like mammals (like us, for example). Growth for plants depends on the temperature (and other things). At low temperatures there is little or no growth; at high temperatures there is little or no growth and there can be death. At some intermediate temperature growth is best. When a SAM stops making new leaves because of the temperature (or drought, etc) biologists call that ecodormant. All daylilies can be ecodormant. When a daylily is ecodormant it might make a bud or it might not make a bud (we do not know). If it does make a bud the SAM becomes that bud. A daylily that is ecodormant, might have green leaves or it might lose all its leaves. What an ecodormant daylily will do, is that as soon as the temperature is better or water arrives it will start to grow new leaves quickly.
There is another kind of dormancy.
When a daylily fan flowers the SAM changes. It stops producing new leaves and produces the scape and the flowers. While the SAM was only producing leaves (a vegetative meristem) it kept growing so that even though part of it became each new baby leaf it did not get smaller. But when it produces the scape (a reproductive meristem) it does become smaller and gets all used up. One or more new SAMs must be made. These can be found, one per leaf at the very bottom of the leaves on the crown. Often only one new SAM develops beside a leaf near the centre of the fan. When the fan has a scape or is flowering that new bud can start to grow new leaves or it can be dormant and not produce any new leaves. When it is dormant the fan will look something like this \\\\\\S////// with the scape (S) in the centre and the old leaves / and \ on either side of the scape. When the bud is not dormant and starts to grow right away the fan will look something like this \\\\\\\///S/////. The new bud could be dormant for a bit of time and then start growing new leaves. If the old leaves start to die while the bud is still dormant and if they all die then the plant may be summer dormant. In those cases, usually the bud starts to grow new leaves after all the old leaves have died. The mature leaves and possibly the scape can be what keeps the bud dormant. That type of dormancy is called paradormancy.
Lastly there is endodormancy.
Many deciduous trees, for example like maples, are endodormant during winter. Many evergreen trees, like pines, are endodormant during winter. An endodormant makes a bud and stops growing new leaves. Its old leaves may die, like a maple tree or they may stay alive all winter like the needles on an evergreen tree. For most species of plants that become endodormant for winter it is the length of the day (or night) that causes the bud to be made and usually the bud must experience a certain amount of cold (to signal that winter has arrived and time is passing) before it can start to grow again. Some species of plants (perhaps apple trees) do not use the length of the day but use cold temperatures to cause the bud to be made. And some species of plants have a fixed pattern that causes the bud to be made . The first bud they make as a seedling for the first winter has a certain number of leaves and after those leaves have grown out a new bud is automatically made and growth stops each year.
Going into winter a daylily might be evergrowing and grow new leaves during the winter. It might be ecodormant and not grow new leaves at all or grow new leaves when the temperatures were warm enough and not grow them when the temperatures were too cold. Or it might be endodormant and not grow any new leaves until sometime in the spring. A daylily that is endodormant will not grow new leaves, even if the temperatures are warm enough and everything is right for growing until after it has experienced its signal that winter has passed (usually a certain amount of cold hours of a certain temperature or days).
I'm in the North. All daylilies are dormant here during our winters. I have brought daylilies inside the house in mid-October, November and mid-January. Every daylily I have brought inside has started to grow more or less right away. That means that no daylily I have tested is likely to be endodormant - they seem to be only ecodormant. Stout took a number of daylily species and early hybrids into a greenhouse in mid-November in New York. They all grew right away meaning that none of those dayliles were endodormant in November in New York. They also were only ecodormant at that time. He kept them growing and some of them went dormant in the greenhouse. Some of those that went dormant did not grow properly after they started to grow. He put some of those abnormally growing plants in cold storage for a month and after he took them out and gave them warm temperatures they grew normally. Those species and hybrids might be endodormants, but they might also not be endodormants and the abnormal growth might have been due to some other sort of problem.
I have two of the plants that Stout used and I have three of the plants that Watkins wrote about in Gainesville, Florida. I have brought all of these inside into the warmth for winter and the growth of the plants matches what Stout found when he brought his plants inside in November (but none have had abnormal growth). They do not seem to match what Watkins saw in Gainesville. To try to understand why they don't match I need more clues about how daylilies grow in Florida during the winter. Fred has helped enormously and I have asked him another question.
With the information from Fred I may be able to put together a logical answer about the differences in dormancy in daylilies inside here and in Gainesville that I can test next year.
