Seedfork said:Ok, I have read more and more frequently "that dormant or evergreen" is not a reliable trait for hardiness. That even dormant or evergreen behavior is very questionable in different gardens. Evergreen plants here in Alabama would most certainly not appear that way in Minnesota. They would most likely behave as dormants, so...my question is should dormant or evergreen even be considered in a program for hardiness, or should it focus strictly on plants that are actually hardy regardless of their foliage behavior in winter.
I am in zone 4 - when I buy daylilies I do not worry about whether they are described as dormant or evergreen since it seems to make no little or no difference on how they survive winter here. I would suggest that you not consider the dormant, evergreen or semi-evergreen descriptions of daylily cultivars when hybridizing and only consider the plants actual hardiness not their foliage behaviour in winter.
So if plants are breed to be more hardy in cold zones, will they end up being more prone to heat dormancy in hot zones?
Not necessarily but it probably depends on the other factors that the hybridizer includes when selecting specific plants to be parents. I interpret "heat dormancy" to mean "summer dormancy". Little is known biologically about "summer" dormancy in daylilies.
One typical growth pattern of a perennial plant would be to produce new leaves in the spring. The plant might stop producing new leaves relatively soon and its leaves would last until fall and then die. It would produce one crop of flowers. Lets assume that this is the pattern for "dormant" daylily cultivars.
Another typical growth pattern of a perennial plant would be to produce new leaves in the spring. It might stop producing new leaves and then flower. Then it would produce a new crop of leaves and flower again. It might then produce another new crop of leaves and flower again. The cycle of new leaves and flowering might be repeated until autumn or cold weather arrived. Lets assume that this is the pattern for "evergreen" daylily cultivars.
Plants cannot control their temperatures very well or easily. How long a leaf will live depends on temperature; lower temperatures allow the leaf to live longer while higher temperatures cause it to die sooner. In cool temperatures leaves may live until they die of "old age" naturally. In high temperatures leaves may die much sooner.
The growth pattern suggested above for "dormant" daylilies suits them to grow in climates that do not have very long and very hot summers. If those types of daylilies are grown in locations with long hot summers it might be that they react by going "summer" or "heat" dormant. We don't know if that is the case. It might be that they go through their normal cycle of growth but because the temperatures are higher that cycle is shortened and instead of the leaves dying in autumn just before winter arrives they die too early in summer.
How long a plant leaf will live depends on temperature (and other factors). High temperatures shorten the amount of time most plant leaves can live while lower temperatures lengthen that amount of time.
