@Xenacrockett
Hi Pat,

I am studying dormancy in daylilies and I hope I may ask you some questions about how daylilies act in your garden so that I can compare that with how they act in my zone 4 garden.

All plants are dormant when they are not growing. In the late autumn and winter in daylilies that means they are not making any new leaves. To make certain when we describe a daylily as dormant that we mean the same thing could you please explain what you mean when you describe a daylily as "pull up the covers and go to sleep"? and "they get active"?

All plants go dormant when the temperatures become too low for growing. But just as daylily cultivars have different size flowers and different size scapes they also have different temperatures that cause them to stop growing (go dormant). Some daylily cultivars may stop growing when the temperature is 41F or below while others may be able to grow at 41F. Some of those cultivars that can still grow at 41F may stop growing at 36F. Other cultivars may still be able to grow when the temperature is anything above 32F and so on.

Unfortunately there is a catch-22 to how plants grow as it becomes colder. Plants grow quickly at higher temperatures but they grow more and more slowly as the temperature gets lower. As an example, imagine if a daylily leaf grows one inch every day at 80F, then it might grow only one inch every two weeks (or perhaps take even longer than two weeks) at 40F. So the colder it is, the more difficult it becomes to be able to tell if a daylily is actually growing very slowly or not growing at all. It would be dormant only if it is not growing at all.

Daylily leaves often become yellow, age and die in the autumn. If a daylily cultivar does not grow any new leaves in the autumn (after its previous crop of leaves have died) we can assume that it is dormant then but we cannot know when it actually first became dormant. The yellowing of the leaves and finally their dying is different from being dormant. A daylily is dormant as soon as it is no longer making any new leaves. Some daylily cultivars stop making new leaves when the scape appears; other cultivars make new leaves until after the scape is visible but stop making new leaves after the last bud opens; some cultivars may stop making new leaves in late July or August or later and other cultivars may never stop making new leaves except when it is too cold.

"Some daylily cultivars stop making new leaves when the scape appears; other cultivars make new leaves until after the scape is visible but stop making new leaves after the last bud opens; "

Maurice,

I observed this on daylilies last year. Is this dormancy of a sort? Meaning the plant as a whole? Do fans on the same daylily without scapes also quit making new leaves? I wondered last year if it was due to the excessive heat and if it might be a sign of the plants weakening. However, sometime after bloom but well before the heat was gone, most of the plants were clearly growing actively again. I'm going to watch this one a bit more closely this year. There seemed to be a definite rest period toward the end of blooming and then a resumption of active growth. I'm not sure it wasn't heat related or tied to another cause though, because that rest period also seemed to be occurring in the plants that did not bloom. It's possible those formed scapes that simply aborted and were still on the same schedule as those with successful scapes.

needrain said:" Is this dormancy of a sort? Meaning the plant as a whole?

Yes, this is dormancy. For some cultivars, growing in certain conditions, it is the only dormancy. For example, in my usual growing conditions, 'Heavenly Harmony' produces its scape in early June and does not make a single new leaf from then until September. 'Ophir' produces its scape in early June and usually does not make a single new leaf until the next year in the spring.

Do fans on the same daylily without scapes also quit making new leaves?

Sometimes they also stop and sometimes they do not stop but continue to make new leaves. Sometimes it is the smaller, juvenile or immature fans that continue to make new leaves.

I wondered last year if it was due to the excessive heat and if it might be a sign of the plants weakening. However, sometime after bloom but well before the heat was gone, most of the plants were clearly growing actively again.

Some growers call that "summer dormancy". However, "summer dormancy" and "winter dormancy" may be the same thing. Often when a cultivar is described as being summer dormant it is because it was dormant around the time of flowering (not making new leaves) but also because the old crop of leaves yellowed and died in the heat of the summer. When the old crop of leaves does not yellow during the heat of the summer but continues to be green until later in the year growers may not notice that the daylily is not making new leaves (and is dormant).

I'm going to watch this one a bit more closely this year. There seemed to be a definite rest period toward the end of blooming and then a resumption of active growth. I'm not sure it wasn't heat related or tied to another cause though, because that rest period also seemed to be occurring in the plants that did not bloom. It's possible those formed scapes that simply aborted and were still on the same schedule as those with successful scapes.

It is possible that the fans that did not bloom had aborted their scapes, but it is also possible that both sorts of fans take a rest at the same time because that is when they have made all the new leaves in that crop.

You might want to watch when the fans take a rest in making new leaves, when the old crop of leaves starts to noticeably yellow and when(if) they die and when the fans start to make new leaves again. In one of my tests of 'Ophir' I took some fans that had stopped producing new leaves and removed all their old leaves. On a second group I removed their scapes and on a third group I removed both their scapes and all their leaves. One group was left alone. The groups that had their old crop of leaves removed sprouted new leaves. On your plants that took a rest toward the end of blooming, heat may have caused the crop of leaves to start to age and decline (yellow). That may have released the fans from dormancy so they then sprouted a new crop of leaves.

In general plants are very flexible in how they grow and daylilies are quite normal in that respect. Young, small, immature or juvenile fans may grow as many leaves as they can in a season while older larger mature or adult fans may only grow a set number (more or less) of leaves before producing a scape. We do not know enough details about how different daylily cultivars grow.

So if a plant dies down after flowering, is it considered dormant??

Hemlady said:So if a plant dies down after flowering, is it considered dormant??

A plant that flowers and then stops making new leaves is dormant (biologically meaning it is not growing). If in addition to not making new leaves its current crop of old leaves yellow and die and it is described as having died down then it is still dormant. When it starts making new leaves (sprouts) it is no longer dormant.

If by "considered dormant" you mean that the plant would be registered as being dormant then that depends on the hybridizer, their location and the time at which the daylily sprouts the new leaves.

Biologically dormancy is a mechanism that plants use to deal with times of the year that may be harmful to the plant if it was trying to grow. Examples of those sorts of times are very cold winters, very hot summers, droughts, etc. Some plants anticipate those times and form protective buds and stop growing before those periods start. For example, neither an evergreen tree like a pine, nor a deciduous tree like a maple, tries to grow during a cold winter. They both grow during the summer, then form buds. The evergreen pine keeps its needles (leaves) during winter while the deciduous maple loses its leaves in the autumn. Often the plants stop growing (making new leaves) a surprisingly long time before winter arrives.

To make certain that the plant does not try to sprout during mild spells in the middle of winter many plants must experience a certain amount of cold (chilling) before they can sprout. For example there are different varieties of apples with different chilling degree requirements and one chooses which variety to grow depending on the amount of chilling the variety requires and the amount it can get in the location where it will be grown.

Stout provided some suggestive evidence that some older cultivars and some species of daylilies might require some chilling to sprout. However, he also showed that by about mid-November in New York no daylily required any chilling to sprout. He did this by bringing a number of different daylily plants into a greenhouse and they all sprouted quickly. I have tested several daylily cultivars by bringing them inside in mid-October and they all sprouted quickly.

This year I will test modern daylily cultivars in mid-September, mid-August and mid-July to check if there are daylilies that require chilling to sprout. I hopefully will also be able to check some daylily species.

So far I have not found any daylily cultivars that require chilling to sprout. That suggests that daylilies are "dormant" during cold periods only because the temperatures are too low for them to be able to grow and not because they are biologically dormant. It also suggests that different cultivars have different minimum temperatures for growth.

I am confused about the "dormant" label on daylilies. True dormants are those that completely disappear (above the soil)
from the spot they are growing in until they sprout new leaves in late Winter/Early Spring?

beckygardener,
I would explain it to you...but I am still trying to figure it out!

beckygardener said:I am confused about the "dormant" label on daylilies. True dormants are those that completely disappear (above the soil)
from the spot they are growing in until they sprout new leaves in late Winter/Early Spring?

Becky, I am not sure that there are any true dormant daylilies. It all depends on what one means by "true dormant". That can be interpreted biologically or just for registration purposes by definition.

Biologically, dormancy has been defined as being of three types, ecodormancy, paradormancy and endodormancy.

(1) An example of ecodormancy is when temperatures become too cold for a plant to grow. All daylilies can become ecodormant. Any daylily could be ecodormant in a cold winter location depending on just how low the temperatures become.

(2) An example of paradormancy is when the growing tip of a plant prevents branches from being made and we pinch off that tip to get the plant to branch. The buds that make the branches were paradormant. Some daylilies may be paradormant after they have bloomed and it may be the old green leaves that stop the daylily fan from growing new leaves (stop it from sprouting).

(3) An example of endodormancy would be when forcing forsythia to bloom inside in the winter one has to wait for the right time to bring the branches inside so that the flower buds on the stems have experienced enough chilling to break their dormancy. The flower buds were endodormant until they received enough chilling and then they were ecodormant because the temperatures outside were too cold for them to grow.

A daylily that completely disappears under the soil is both dormant and deciduous. It is dormant because it is not growing any new leaves and it is deciduous because it has lost all its previous leaves.

The daylily dictionary (http://www.daylilies.org/ahs_d...) defines "dormant" as:

"DORMANT:
For AHS registration purposes, the term "dormant" refers to daylilies that lose their foliage completely before or shortly after frost and over-winter with pointed foliage buds, usually just beneath the soil surface. Dormants will resume growth in spring.

However, in plant science, the widely accepted definition of dormancy is a temporary suspension of visible growth of any plant structure containing a meristem*. Thus technically the term “dormant” is not restricted to deciduous plants but applies also to evergreen plants, which can retain their foliage while having dormant buds. All daylilies, regardless of foliage habit, are capable of cold temperature dormancy in the technical sense where it gets cold enough to suspend growth."

The AHS registration page (http://www.daylilies.org/AHSre...) defines dormant as:

"Dormant (dor.)
These daylilies lose their foliage completely before or shortly after frost and over winter with pointed foliage buds, usually just beneath the soil surface. Dormants will resume growth in spring"
= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
I interpret the definition for dormant for daylily registration to require a cultivar to be both deciduous and endodormant (because if they were only ecodormant they could resume their growth before spring simply depending on the temperatures during different times in winter in different locations or in different years).

That may be a problem as I have not found any cultivar that I have tested to be endodormant - so far they have all been only ecodormant. That includes cultivars that act dormant in Florida, such as 'Hyperion' and 'Taos' and cultivars that act dormant here in zone 4, such as 'Ophir'.

Maurice - Thank you for taking the time to try to explain the "dormant" label on daylilies. I get what you are saying.

Then this leads me to another question ....

I KNOW I have dormants as described by the AHS. Almost always, after about 3 years, these plants disappear completely. I assume they just shrink little by little each year until they have decreased so much that they literally die. Is this typical of a true dormant daylily growing in central Florida climate or is something else possibly killing them? I have other daylilies growing near them and they don't die but continue to grow and bloom each year. The dormants will also bloom until they no longer come back. I wouldn't say they put on a great flush of blooms, but they do bloom. The returnee daylilies do not appear to be overwhelming the dormant plants into extinction from what I can tell.

This topic about dormants always has me confused because of what I am growing and observing in my garden beds.

beckygardener said:Maurice - Thank you for taking the time to try to explain the "dormant" label on daylilies. I get what you are saying.

Becky, you are very welcome.

I KNOW I have dormants as described by the AHS. Almost always, after about 3 years, these plants disappear completely.

Can you please tell me the names of as many of those dormants (that are registered) as possible so that I can consider testing them.

I assume they just shrink little by little each year until they have decreased so much that they literally die. Is this typical of a true dormant daylily growing in central Florida climate or is something else possibly killing them?

A "true dormant", that is an endodormant that requires some amount of chilling to break its dormancy, may act that way in locations where it does not experience enough chilling to completely break its dormancy. For those types of plants and in those locations they may not grow properly after winter. Some may not flower, some may not grow to their normal height, some may have deformed leaves, some may flower but have deformed flowers or fewer flowers, etc. In other words they grow abnormally if they do not receive sufficient chilling. Some buds may never sprout if they do not receive sufficient chilling. If that is the case then they may dwindle away with fewer and fewer buds each year. But that assumes that a large mature plant with many buds arrived from somewhere else where it did receive sufficient chilling and then is grown in a location where it does not receive enough chilling.

On the other hand there are other possible, completely different reasons why a cultivar that is registered as a "dormant" may not grow well in locations with warm winter climates.

There is a history of daylily hybridizers in warm winter locations choosing to hybridize more for daylilies that remain green during winter ("evergreen") and of hybridizers in cold winter climates choosing to hybridize more for daylilies that go completely down for winter ("dormant"). But there are other, possibly more important differences between locations that have mild winters and those that have cold winters. One of these is how hot it becomes during the summers; another may be how dry it becomes during the summers, etc.

Many years ago, Moldovan, who hybridized in Ohio, and Munson, who hybridized in Florida, began to swap cultivars. Apparently neither was happy about the way their registered cultivars grew in the other location. So Moldovan began to include daylilies registered as "evergreen" and "semi-evergreen" by Munson and Munson began to use daylilies registered as "dormant" by Moldovan. They were aiming to produce daylilies that were better adapted to grow in both regions rather than daylilies that were very well adapted to grow only in their own regions and poorly adapted to grow in other regions.

In general, a hybridizer can only easily produce plants that are well adapted to their own regions and conditions. Usually, the better adapted a plant is to its growing conditions the worse it is adapted to conditions that are different from those. The more different the growing conditions are to those where it was hybridized the worse adapted the plant is.

Typically, cultivars that are hybridized in the northern, colder winter areas will be better adapted to those conditions and not as well adapted to conditions in southern areas while those hybridized in the southern warmer winter areas will be better adapted to those conditions and not as well adapted to conditions in the northern areas.

Daylilies do not necessarily grow very well at quite high summer temperatures. Arisumi did some research on this. Unfortunately he only used one cultivar but it provides a good example. He used 'Purity'. All the AHS registration information for Purity (Traub, 1949) height 45in (114cm), season MLa, Diploid, Fragrant, YM1: Yellow medium self. [note the lack of registered foliage designation].
Arisumi grew 'Purity' at constant temperatures of 55F, 65F, 75F. 85F and 95F.

At 55F the plants grew slowly and did not reach maximum size during his test period.
At 65F the plants reached maximum size in 3 months. At 75F the plants reached maximum size in 2 months. At 85° and 95° the plants grew quickly for three to four weeks and then yellowed more and more. The older leaves dried and died more quickly than at the other temperatures.

He tested 24 plants at each temperature. All 24 plants grown at 75F bloomed. Only four of the plants at 85F bloomed and no other plant bloomed.
Constant temperatures of 85F and 95F were not optimum for 'Purity'. A temperature of 75F was better.

It is possible that daylilies that are registered as "dormant" or act "dormant" are better adapted to more moderate summer temperatures and are poorly adapted to hotter summer temperatures. That may be one reason why they may dwindle away in locations with mild winter climates. They could be better adapted to the moderate summer temperatures because they were hybridized in locations with fewer extreme temperatures or lower extreme temperatures during summer or because they were hybridized from parents that were hybridized in similar conditions.

Looking great, Kelli!

@admmad Maurice, maybe it would be a good idea to start a new thread on this topic, so that others will find it. It is very interesting, and I'm sure that others will have questions, or would be able to report their findings.

Maurice - Unfortunately (or maybe fortunately) my daylilies are 98% hybrids grown from seed here in my yard. I might be able to share the names of some of the newer seedlings, but not the older ones (lost the tags and parent name trail long ago). So this is a case of possible genetics for me, not what the plant was used to. Which would probably mean that the genetics of that hybrid require colder winters/milder summers. But here is the other issue, some of those are in a partial shade area. They are planted with other daylilies in the same raised bed. The other daylilies seem to do well there, but these "dormants" don't. So ... over 75 degrees they may be struggling. You have shared some VERY interesting info about the experiments that Moldovan and Munson did. I, for one, would be interested in more discussion about this topic. Being a novice, I have a LOT to learn!

It probably would be a good idea to start a new thread about this string of discussion. Could we copy and paste the info that you already shared in this thread into a new thread? I know others would indeed be interested as this issue has come up before but the discussion didn't go as far. Do you want me to start a new thread or can you do it and post the thread link on this thread to redirect others there? I don't mind doing it, just let me know.

@Natalie, @beckygardener

OK, I can start a new thread and copy/paste the information I have posted from this one to the new thread. Any suggestions for a title to the new thread?

Thank you Char, for creating the new thread and moving the posts.

Title should have something about daylily "dormancy" in it, so anyone as interested as I am, can find it immediately.

Something like, "What's the real truth about Daylily Dormancy?"

beckygardener said: But here is the other issue, some of those are in a partial shade area. They are planted with other daylilies in the same raised bed. The other daylilies seem to do well there, but these "dormants" don't. So ... over 75 degrees they may be struggling.

Becky, just for information, the temperatures that weather forecasters report, are actually measured "in the shade". The thermometers and other instruments are placed in special boxes, called Stevenson screens. These have slots in their sides so that air can pass freely through them and are painted white to reflect sunlight and eliminate (or reduce) its heating effect (see http://www.weatheronline.co.uk...).

Char - Thank you for starting a new thread for the topic of daylily "dormancy"!

Maurice - Well how about that! I learned quite a few new things today! I did NOT know how weather temperatures were measured. So that actually means it is hotter than what the weather reports say! Yikes!

One thing I am now noticing in my daylily gardens ..... much of the "older" foliage is turning yellow, then shriveling up and changing to brown. The older leaves are dying as the new ones grow in. Is this because they are coming out of Winter dormancy (including evergreens and semi-evergreens) and putting out new foliage?

Can daylily plants go dormant when they are not receiving enough fertilizer?

This is a photo of a dormant daylily putting out new leaves (2 fans) in my garden. The daylilies around it are still tall and green but this one almost disappeared below the soil line and is now waking up and growing new leaves. This is a close-up, so the plant fans are still very small. I could see where it was as there was this tip of green showing through the soil for most of the Winter. But we did not have a cold winter. A very mild winter in central Florida this year. This is one of my older (unknown) seedlings.