This is going back to a much earlier post on this topic... just catching up on this subject. Regarding the cultivar, 'Alan Lane Agin,' although it is registered as dormant (deciduous), it has NEVER behaved that way here in the mid-Atlantic, since it was purchased from the hybridizer when she first introduced it. It does not look at all like the other deciduous daylilies here , as it tries to grow whenever the weather moderates a bit, a trait more associated with evergreens. I just checked it earlier today and new tips of foliage are not peeking out like one often sees with the deciduous daylilies at this time of year, rather foliage is crusted in brown half dead foliage with traces of green underneath. Although it may have behaved differently in AL, it is definitely an evergreen here!

sooby said:Maurice, I thought Ken raised an interesting question. When I looked at Arisumi's paper it does not appear he lowered the temperature at night.

He may not have lowered the temperatures at night.

A researcher testing the effects of a given temperature has to make choices. For example, to test the effects of 25C one could grow the plants at a constant temperature of 25C or grow the plants at two different temperatures (night versus day) to produce observations equivalent to constant 25C - [16 hours day @ 25.5C plus 8 hour night @ 24C OR 16 hours day @ 26 plus 8 hour night @ 23C, etc. OR one would have to change the question to the effect of differences in daytime temperatures with night temperatures held constant, eg daytime temperatures of 15C, 20C, 25C, 30C, 35C, with night time at say 20C. Then repeat for the daytime temperatures and set the night time to a higher temperature, etc.

Some researchers choose to simply test at constant temperatures.

Anyway, disregarding that, are you basing your assessment regarding detrimental temperature on air or soil temps since, as Ken surmised, with the potted plants in Arisumi's study they would both have been the same 24/7?

Every controlled experiment with plants that is conducted in a growth chamber, a greenhouse or in pots under most circumstances is faced with soil not being in the same state as that in the field. Controlled experiments tend to be "unnatural" in many respects.

As far as soil temperatures being different from air temperatures there is also the problem that air temperatures are not the same as plant temperatures under a shining sun, etc. Do soil temperatures track air temperatures although with a lag time? or are they always different? Are they always cooler or are they always hotter than air temperatures? Or does it depend on the soil, watering, mulch etc. [Note , the answers to these questions are not relevant to their purpose.]

Arisumi's results show that some daylilies suffer from high temperature stress. Plants have base temperatures for growth, they have optimal temperatures for growth and they suffer stress at appropriately high temperatures. That is, we can expect that some daylilies will, just like other plant species, suffer from high temperature stress at appropriate high temperatures.

Below is an example of published research looking at the effect of temperature on root growth in pine.



The graph shows that pine seedlings have an optimum soil temperature for root growth. Completely to be expected. It is likely that nearly all plant species that grow in more or less typical soil will have an optimum temperature for root growth. The optimum appears to be around 75F. Should I take anything away from this other than pine seedlings are typical, they grow in relation to temperature, as expected, they have an optimum temperature, as expected and that the optimum was not either very low or very high?
No.
At the bottom of this post are the methods used in the research. Do they resemble anything in nature? No. If the research question was investigated by another researcher would they find the same optimum temperature - probably not. Would they find the same general pattern of growth in relation to temperature - probably yes. If they repeated it with pine seedlings of a different genotype even with exactly the same methods they probably would not find the same optimum.

Much of the research Arisumi and Stout did was not aimed at anything more than general understanding of daylily biology - preliminary studies to learn about the basics. The basic result from Arisumi's temperature research is that daylily growth responds to temperature in the same way that other plant species do. Daylily growth will have an optimum temperature and at temperatures both below and above that optimum growth will be less. At some temperature above their optimum, daylilies will suffer heat stress. It is unlikely that any of the specifics of his design would make a radical difference to those conclusions.





Methods for the root growth- temperature study
The seedlings were grown in glass tubes about two inches in diameter
and 18 inches long. These tubes were closed at the lower end with rubber
stoppers and a layer of cinders placed over the stoppers. The tubes were
then filled with a loamy greenhouse soil, which was kept wetted to field
capacity. Although the soil was heated in an electric sterilizer before use,
it still contained two species of small animals, a nematode and a collembolan.
Neither seemed to be harmful; apparently they fed only on dead
tissue sloughing off the roots. The collembolans may have aided in aeration
by opening small passageways in the soil.
The soil atmosphere in the tubes was analyzed with a Haldane apparatus
and found to have approximately the same concentration of oxygen as
the outside air. The concentration of carbon dioxide in the soil was somewhat
higher than outside. The average amount was 1.0% and the maximum
2.88%. CANNON and FREE (6) reported that for several species there
was no detrimental effect on root growth of 20% or more carbon dioxide if
oxygen were not deficient. Since the soil atmosphere normally contains
more carbon dioxide than ordinary atmosphere and excesses from 0.2 to 5%
are not unusual (28), it is believed that growth was not abnormally influenced
by deficient oxygen or by an excess of carbon dioxide.
In the first series of experiments, the seedlings were started from seeds
planted in the tubes, but this proved unsatisfactory because the seeds did
not germinate uniformly. Seeds for the second series of experiments were
germinated on moist sand, and three seedlings were transplanted to each
tube. About two weeks at 20C were allowed for the seedlings to become
established before an experiment was started. The tubes were supported in
racks at an angle of about 40 degrees. This caused the roots to grow along
the lower side of the tubes where they were visible and could be measured.
Measurements were made for a period of three weeks for each series of tests.
Soil temperature was controlled by immersing the racks and tubes in
large tanks of water equipped with refrigeration and heating units, controlled
by thermoregulators and relays. To insure uniform temperature
throughout, each tank was equipped with a stirring unit which operated
intermittently. The variation in temperature was less than one degree
centigrade.
Four tanks were operated simultaneously. The tanks were covered with
pieces of insulating board containing holes for 12 tubes. Even though these
covers were not entirely light-tight, not enough light entered to permit the
growth of green algae in the tubes, and it is, therefore, believed that such
a low intensity could have had no significant effect on root growth. Although
considerable variations in air temperature and humidity occurred in
the greenhouse room where the tanks were located, all plants in a series
were exposed to the same variations.

Maurice - As always, thank you for the time you put into trying to explain daylily growth to me and everyone. It's sinking in.

Arlene - So you mainly grow EVs?

Here is my daylily bed a week later from my earlier photo post. I am amazed at the foliage growth. There are 9 dormants in there. No scapes that I can detect yet, but I know it won't be long. I can't wait! I am ready to see some bloom here for the first time!

My new raised key-hole daylily bed showing a week's growth!:


And another new smaller raised bed in front of my vertical herb garden. I wrote an article here on ATP about the vertical garden. The plants in that herb garden are the original plants from 2 years ago. I can't believe they have survived my hot summers (with watering) in such small garden boxes. Herbs and daylilies are tough plants! :

I love your vertical herb garden! Great Idea! Your gardens look very nice! I can't wait till my gardens are green and alive again. You have given us Northern gardeners hope.

Karen - I was honestly amazed at the growth of the daylilies in just 1 week. They are really looking good. I do have rust on some of them. (I need to mark their names in my journal for future reference.) But most of the daylilies show NO signs of rust at all. Looks like I might officially have some registered daylily "clumps" this year for the first time ever. It appears in photos that clumps are what really show off a cultivar. (Not single or double fans.)

Julie, I grow Alan Lane Agin here in east-central Georgia and it is a true "dormant" for me, losing all of its leaves and staying underground from November until at least February. Then the blue-green foliage begins to appear, but then it seems to hesitate until temperatures warm a little more before starting to really take off. Interestingly, many of its seedlings show similar "dormant" tendencies even when crossed with an evergreen or a semi-evergreen.

However, Venus Flytrap which is registered as a dormant never loses its leaves here during the winter and basically stays green all year. I have seen others express the same behavior with this cultivar.

One last comment - - I have two mature (7+ years) seedling siblings from the cross Leslie Renee X Cerise Masterpiece, both of which are registered as semi-evergreen. Both of these parent cultivars have dormancy in their parents. One of my seedlings is an evergreen and the other is a dormant. In fact, the dormant seedling is the very last daylily in my garden to make an appearance every spring though some of my cultivars that are registered as "dormant" appear earlier but bloom well after that seedling. That kind of thing makes tetraploid genetics a complete mystery to me. Oh, by the way, Shores of Time is a sibling of Leslie Renee and although it is registered as a dormant has never lost its leaves during the 9 winters it has lived in my garden including a couple that actually reached the mid-teens in temperature.

I live in North Carolina, USDA Zone 7b---not really "Southern", but not "Northern" either. The problem with dormants here is: dormants are very resistant to freeze damage while in the dormant state. However, once growth gets going, the new leaves are less and less able to tolerate freezing. A few years ago we had an unusually warm spell in March/April that lasted for a couple weeks. Then, we had a week where the low temps were in the low twenties down to teens. The Dormants suffered as much as the Evergreens.
I think the problem with trying to grow dormant daylilies further south is the problem of varying temps between daytime highs that start growth--and nighttime lows that repeatedly damage the plant until it gives up. Evergreens seem to bounce back quickly from mild freezes--but if they freeze to the ground--they are pretty much done for. Some Evr's have more antifreeze and can stand the extremes of cold---but they are rare. Every winter I lose at least a half dozen plants. 4 out of 5 are EVR unless there are no lows below 17 degrees. Then it is an even split between Evr's and Dor's.

Becky, I agree, clumps of blooms look a lot better than a couple fans blooming. Your garden is going to beautiful during bloom season! I can't wait to see your clump pictures. Congratulations!

Larry, Leslie Renee goes underground dormant here in Ohio. It's interesting how different daylilies can be in different climates.

Becky, I remember you posting about your vertical herb garden when you were building it. I love it.

Karen and Cindy - Thank you.

Greg - Even living in zone 9b/10a, I get paranoid each Winter. (We've had Winters that were very cold for our zone.) I tend to cover my daylily beds with sheets on the coldest nights. (Some of my tropical plants do get frost burn.) I see mine putting on new growth and don't want a cold night or two to harm that growth. But even with that, I still lose a few of my daylilies every year. I always assumed they were daylilies that were on the "dormant" side. Though now, I am wondering if I over-hybridized such young plants or they developed root rot or some other malady.

It seems no matter where you live .... daylilies aren't always the tough suvivors as I once thought.

beckygardener,
Sorry to be so late responding, but I am just now catching up after being gone for over two weeks.
I have over 30 dormants in my garden at the moment, but none of them have been here more than three years with maybe the exception of Flore Pleno (I really don't know how long I have had it). I have also had a few more dormants but they did not last very long.
Alabama Jubilee
Apple Tart
Bertie Ferris
Carnival In Mexico
Chicago Apache
Corryton Pink
Crimson Pirate
Endowed With Beauty
Erin Lea
Femme Fatale
Flore Pleno
Fooled Me
Happy Returns
Highland Lord
Hot Wheels
Hush Little baby
Jason Mark
Lavender Stardust
Mexican Sunrise
Mini Pearl
Omomuki
Panic In Detroit
Primal Scream
Rainbow Candy
Red Volunteer
Scarlet Gown
Siloam Double Classic
Smokey Mountain Autumn
Sunday Gloves
Tiger Kitten
Wineberry Candy
Zagora
All of these have returned though at least one winter now. Many of them for two seasons and a few for three seasons. All of these are presently living in the garden, a few look very vigorous and a few look to be what I would call at the present time "weak". I will have a much better idea how they will perform after this season being so many of them have only been here since last spring or even just since this fall.
I do know that Red Volunteer does very well in this area. Chicago Apache seems to be fading slowly over the years, but I do need to see it perform this year before condemning it too much.
Happy Returns does not seem to be very happy at all in my garden.
Lavender Stardust was new last year, but it is very vigorous looking already, huge dark green leaves. I have three different Zagora clumps and they seem to be going strong.
A few that seem to be weak so far (just keep in mind it is early in the season for dormants):
Bertie Ferris, still very small.
Corryton Pink, seems weaker than last year.
Jason Mark, nearly died due to several difficult circumstances but is making a very small comeback.
Panic In Detroit seems to be weak at present.
Primal Scream is still looking puny, but I have seen it growing in gardens near by and expect it to do well, even though it is lagging behind at the moment.
Smokey Mountain Autumn seems to be struggling and is pretty small.
Tiger Kitten is also lagging and looking pretty tiny at pressent.

Larry - Thank you for your list. Please do report how yours do this year as the season progresses.

Good morning Becky and everyone...

I thought that I would report that all of my listed dormant's have rebound from their resting phase and are putting on new growth. I also reported in my earlier post that 'Lake Norman Spider' has never produced or grown well here. Well it must of heard me because it has responded and even put up a new fan.

It's currently in a 1 gallon pot but will soon find itself in a more comfortable and larger 3 gallon container. Below is a photo, taken yesterday...

I just posted photos of all my dormant daylilies in my ATP blog, all but Happy Returns have returned, maybe it will show later. The photos were all taken this morning and it will give a good gauge of how different the progress is of the dormants I grow.

This has made me pay more attention to the foliage habits of all the daylilies. I have two beds side by side both almost all seedlings. One bed was mostly evergreen and the other mostly dormant. We have had some nice weather for most of March and the dormants have just taken off. The dormant bed looks much better than the evergreen bed.

I also looked up some of the dayliles I grow and find them registered as SE. In my garden they are definitely evergreen not semi-evergreen. The ones I have looked up don't even get a discolored leaf.

While nothing is 100% the case, I find that most of the daylilies that are particularly poor performers in my garden are evergreen.
I do wonder if daylilies establish their foliage type from their beginning. I notice small baby seedlings looking green their first winter, but after they grow into larger plants they will have the foliage die back.. For example, I planted hundreds of seedlings in 2015 and all the babies were green all winter. I would say that there is no way that are all evergreen. Many of them have had strong growth in March that is similar to the many dormant cultivars in our gardens.

Becky:
I have been reading this thread. Don't know if zone 7a is far enough south. About 42% of my Daylilies are dormant. The years hybridized start in 1934. I have Red Volunteer, it was one of the first plants purchased in 2004. It has bloomed consistently for me every year around the 4th of July. Last summer was a hot one, with not a lot rain in June and July and the 2015 winter was fairly mild. Red Volunteer is growing it will be interesting to see how it does this season. Also, have Razzmatazz, Happy Returns, Silome Double Classic.......they have all performed well.