@bobjaxWant to read a PDF by one of my daylily heroes?
Thank you. I have read it before. There is much to commend him for but not statements such as this one,
"The 3 most popular daylily varieties, 'Stella de Oro', 'Pardon Me' and 'Happy Returns', suffer in Southern California. They are deciduous (no foliage) for 3 months and require freezing winters. On the other hand, our evergreen winter-blooming varieties would freeze to death in Maine."
I expect that 'Stella de Oro', 'Pardon Me' and 'Happy Returns' do indeed suffer in Southern California but not because they require freezing winters.
Although until this year I had not tested 'Stella de Oro', 'Pardon Me' or 'Happy Returns', I have tested other daylilies described as being dormants that require freezing winters only to find that they do not. A couple of weeks ago I brought 11 'Stella de Oro' plants inside. They were all dormant with buds and all their leaves dead and dry or drying. They all started into growth within a couple of days of being brought inside. They have had no special treatment to break their dormancy. They did not require winter cold. I will put them back outside next year in late spring after the chance of sufficiently low temperatures have passed. They will do fine as did "dormant"/deciduous seedlings from Stella that never experienced winter cold.
'Stella de Oro' does not appear to require cold to break its bud dormancy and to grow and flower normally. (Researchers examined it and five other daylily cultivars, none of which required winter cold to flower).
I am in borderline zone 4/5. I have never bothered to worry about (or even check) whether a daylily is registered as an "evergreen" (actually evergrowing) or not when purchasing daylilies. The daylily growth forms do not determine hardiness. I do not even know how many "evergreens" I currently have growing in my field but I expect that it is a reasonable number. And they do not as a group have a problem in surviving zone 4 winters. That does not mean that they are all necessarily equally hardy but then that applies to so-called "dormant" daylilies as well.
It is not difficult to understand why some daylilies registered as "dormant" might not do well in some southern locations. High temperatures during the growing season may be detrimental to their growth and development. They may be unable to make and store sufficient reserves during the growing season to manage their normal winter (dormant - no growth) period normally. Even worse, the normal winter rest period in those locations is not conducive to rest. Plants do metabolize (use reserves) at low temperatures, although presumably very minimally the closer the temperatures are to 32F/0C. However, in locations with mild winter climates the temperatures may be well above those and the dormant plants will metabolize (respire) and consume more reserves (dormant plants can be metabolically active - that depends on the temperatures - they just do not grow).
