Foliage Habits
of Daylilies
Brian Reeder
Foliage habit is an interesting subject that I often spend a
lot of time thinking about at this time of the year. I am in my garden every
day, regardless of the cold or weather, as I have to feed and water my birds
and that allows me to make observations of foliage type throughout the winter
months.
An evergreen cultivar on the left and a true dormant cultivar on the right from my garden on 12/18/2014
To start this article, let’s look at how the AHS defines the
foliage categories. From the AHS FAQ page we find the following:
What are the
foliage traits of daylilies?
Foliage traits of
daylilies include color, size, habit, and cold-hardiness and heat-tolerance.
Color
The foliage of
daylilies can be blue-green to yellow-green or any shade in between.
Size
Daylily leaves vary
considerably from slender and grass-like to husky, wide, and nearly corn-like.
The leaves may arch, or may stand nearly erect. The length of daylily leaves
ranges from as little as 6 inches to 36 inches or more.
Habit
The winter behavior of
the daylily foliage is called "the foliage habit." For registration
purposes, the foliage habit is loosely categorized as dormant, evergreen, and
semi-evergreen.
- Dormant. The leaves of these daylilies die
completely back as winter approaches. They stop growing and form resting buds
at the crown, and the foliage dies down naturally and gradually. In the spring,
the resting buds have a distinctive spear-like appearance as they emerge.
- Evergreen. These daylilies retain their leaves
throughout the year. They do not form resting buds. Instead, they continually
produce new leaves unless cold weather prevents growth. In mild climates, the
leaves of evergreens remain green all winter. In the coldest climates, the
foliage of evergreens nearly always is frozen back, but the crown survives if
it is hardy (or well mulched).
- Semi-Evergreen. Today, the term semi-evergreen is used to
describe any foliage behavior that is not readily classed as simple evergreen
or dormant. Originally, the term semi-evergreen (or conversely, semi-dormant)
was used to describe those daylilies that retained many of its leaves and
appeared somewhat evergreen when grown in the South, but lost all its leaves
and went dormant when grown in the North.
Cold-Hardiness and
Heat-Tolerance
The cold-hardiness of
daylilies is quite variable. Some are ironclad hardy. Others are extremely
tender. Cold-hardiness is not determined by the foliage habit. Evergreen,
dormant, and semi-evergreen can be anything from extremely cold hardy to
extremely tender. To avoid risk of losing a cultivar, choose daylilies that
others have already grown successfully in your climate.
I think this is a very good description of the three foliage
habit registration categories. I agree with the definition of dormant and
evergreen and I think the description of semi-evergreen is particularly good in
that it acknowledges this category as basically a catchall for anything that is
not a true dormant or extreme evergreen. Further, the difference between
foliage type and cold hardiness is defined.
It is a common habit of humans to generalize, and so we
often hear generalizations such as ‘all evergreens are tender’ or ‘all dormants
are cold hardy’, but these generalizations are not always true. There are cold
hardy evergreens and tender dormants. It is important to remember this. At this
point, the genes of the original species are so blended and recombined that
almost any combination is possible.
I would also point out that in truth the semi-evergreen
category is something of a generalization. There really is no such thing as a
‘semi-evergreen’ speaking from a genetic standpoint, though I don’t blame the
AHS for using the category. It is a convenient generalization that is useful
for registry and can encompass all the in-betweens in one classification. The
only problem I see with the classification is that a lot of people seem to
think it is a real thing that is absolutely definable, rather than a broad category with a lot of variation.
On the left is a clump of Ancient Elf, a true, hard dormant photographed in my garden on 12/18/14. It almost appears that there is nothing there and if you dig through it, the resting buds are almost completely underground. On the right is the same clump in bloom summer 2014.
In truth, there are only two foliage habits - dormant or
evergreen. Anything that does not go completely dormant in the winter is an
evergreen, technically speaking, though the 'evergreen' range is very variable. However, as daylily cultivars are hybrids of
several wild species of daylily, the genes of those species are recombined into
unique combinations in the hybrids and expressions that are not seen in the
species can occur.
Those cultivars that we call semi-evergreen are likely the
expression of both evergreen and dormant genes interacting within the one
genome. It is highly unlikely that single genes control all foliage habits
amongst the species and so there are probably major genes and minor genes (or
modifier genes) at work to create the foliage habit expressions we see in the
species and their hybrid descendants. It is generally accepted that evergreen
foliage habit is dominant to dormant foliage habit (likely the action of some
of the ‘major’ genes).
So a semi-evergreen may be a heterozygote for both types of major
genes with evergreen habit predominating but not fully expressing (this could also
be due to a dosage effect), or we may see some instances where a homozygote for
evergreen also has one or more modifier genes coming from dormant ancestors and
thus don’t express the evergreen genes fully. There are also likely combinations
of both examples. As well, there are undoubtedly homozygous dormant cultivars
that have some evergreen modifiers and so are something of a ’semi-dormant’,
being far closer to a dormant than anything else, but not a real, true, hard
dormant. These frequently (though not always) get registered as ‘dormant’.
A true evergreen seedling (Substantial Evidence x Kaleidoscopic Intrigue) in my garden photographed on 12/18/2014
However, to fully understand the foliage habit of daylilies,
it is important to give some consideration to the species from which they all
derive. There are dormant and evergreen species amongst the Hemerocallis genus.
The dormant species are mainly true dormants that perfectly fit the description
for dormant as per the AHS. An example of this type is H. dumortieri.
The evergreens however, are a different matter. They are
much more variable, ranging from the tender and fully evergreen H. aurantiaca
and its clone Major to the group that I would consider ‘conditional evergreens’
such as the many clones of H. fulva, H. citrina. In these
later species the foliage is usually evergreen in warm winter climates while going
dormant in cold winter climates. It is also interesting to note the AHS
description of semi-evergreen says this type of habit was the old definition of
semi-evergreen. A few clones of some of the species can actually maintain evergreen foliage while forming a resting bud in cold climates. The fulva clone Chengtu is an example.
Even in Stout's day, when they were only dealing with
species and the very earliest diploid hybrids, it was noted that some of the
evergreen species could not survive in the north, or did very poorly.
From Daylilies by A. B. Stout 1934, regarding Winter Injury
on page 99 of the 1986 edition - "In the northern part of the United
States and further north daylilies which have evergreen habit of growth usually
suffer to some extent from winter injury...In the region about New York there
is usually a protection of snow for only a small part of the winter and there
is an alternation of freezing and thawing temperatures. When spring arrives
many of the exposed leaves have been killed and some buds may be dead... The H.
aurantiaca clone Major suffers so severely from winter injury that is usually
does not survive the winter throughout the northern United States. Many seedlings
obtained by hybridizing H aurantiaca and (its clone) Major with more hardy
daylilies are not fully hardy."
On page 100 in the section 'In semi-tropical and tropical
countries', he states, "In the southern states the types and varieties
which are evergreen or nearly so, are said to be most satisfactory."
So from the very beginning, there was a noticeable
difference in the most hardy, dormant species and the most tender of the evergreen
species, with some evergreen species being impossible or nearly impossible to
grown in the north. This is just a fact of the evolution of the species in
their native ranges in Asia. We can't expect that all evergreen cultivars,
descending from those semi-tropical evergreen species, are going to suddenly
'get hardy'. Some evergreen cultivars are very hardy, and probably due to cold
hardy dormant species deep in their ancestries or from the presence of hardy
types of evergreens such as H. fulva or H. citrina in their background. Others
are not hardy and that has a lot to do with the genes they have inherited from
tender evergreen species in their backgrounds.
Because there are different variations of evergreen foliage
habit amongst the species, as well as the true dormants, and crossing these
species widely made the hybrid cultivars, we have an even wider array of
foliage habit expression in the hybrids than we do in the species. Some of our
cultivars perform exactly as the species do in regards to foliage habit, but
some fall in-between their species ancestors.
Foliage habit, in and of itself, does not touch directly on
the subject of cold hardiness, as the AHS text above points out very well. Cold
hardiness seems to be determined by genes other than those that determine the
foliage habit, though those genes would also derive from the wild species in
the ancestry of the hybrids. While it is true that there are hardy evergreen
cultivars, it is also true that some evergreen cultivars will not perform at
their maximum capacity in areas of cold weather due to the stress they must
endure through the cold months of winter, even though they survive from year to
year and bloom. An example of such suppressed performance would be reduced
branching and bud counts or scape heights. There are however some evergreen
cultivars that simply won’t survive in northern climates.
In my own experience with around 800 cultivars, I have only
lost a tiny handful of evergreen cultivars outright to cold. What I see more
frequently is suppressed performance, occasional loss of a few fans, reduced
branching, bud counts and scape height. Because I am in an area that can be
very cold or very warm in the winter, each year can be variable. However, my
area almost never has the snow cover that more northern areas benefit from and
so some evergreen cultivars are hardier both further north and further south
than they are in my Kentucky garden. This can come as quite a surprise to folks
not familiar with our variable winter weather and late, often devastating
frosts.
A particularly bad combination here is cultivars that are
evergreen and are early-early blooming. We frequently have late frosts, but we
may get very warm as early as March and have full growth very early with scapes
beginning to form on the earliest flowering cultivars by the beginning of May.
When those late April and early to mid May hard frosts occur, this causes
considerable damage to those early blooming evergreens and the entire first
round of scapes may be completely destroyed or severally damaged. When those
cultivars are also rebloomers, then the later bloom scapes will be fine, but
for those first ones these late frosts are a disaster. There are very few years
when we don’t have an episode of late frosts, so this damage is something I see
almost every year. I do want to stress though that this does not mean these are
‘bad’ plants. I fully understand why the early-early evergreen cultivars are
very desirable in more southern settings. They just aren’t the most suitable cultivars
for my climate. In spite of that, I am still using some of these, especially
strong rebloomers, in my breeding program. I am just careful about what I cross
them with.
With that said, though, I want to stress that I buy and grow
evergreens, usually bred in the deep south, making them a part of my breeding
program and fully intend to keep growing them and breeding from them. While I
personally prefer hard dormant cultivars, I want to produce plants that can be
grown successfully in climates other than my own, both north and south. Another
thing I keep in the back of my mind is that one can never tell how the climate
may change over time and should we become warmer and warmer, hard dormants may
start to be less viable here than the more evergreen cultivars. No one can know
what will happen, and I certainly don’t claim to know, but I like to be
prepared for all eventualities. Another thing that I take into consideration is
that there is generally more information on the rust resistance of plants bred
in the south than there is for plants bred in the north.
In my own garden there are very successful evergreens. I
have grown Nivia Guest, for example, for over twenty years and it has never
shown any problems. I would also point out that it is not a very early blooming
cultivar, so I think this helps make it more successful as a garden flower, but
the plant never reduces in fan count here in even the coldest winters. Other
evergreens don’t do as well, and a few do really poorly, decreasing every year
and showing infrequent bloom scapes only after the very mildest winters. However,
some of these are still a part of my breeding program, even if only in a very
limited way.
There are many reasons to use these cultivars. The southern
breeders can go through their generations much faster than most of us in
the north can (except perhaps where greenhouses are used in the north), and so
the southern breeders are almost always ahead of everyone else in terms of
flower trait advancements. Those advanced flower genetics are reason enough
alone, but there are also other reasons. For me, the known rust resistance of
some cultivars from the south is a huge necessity, as most northern growers
can’t test for rust resistance so the results of their programs are far too
often an unknown quantity. Finally, using the southern evergreens over northern
dormants can often produce both foliage types, as well as the in-betweens so plants can be produced that may flourish in the south or in the north, and
sometimes you get lucky and get a plant that flourishes in both extremes. Using
the southern evergreens over northern dormants is a long-practiced,
tried-and-true method. Just look to Curt Hanson’s amazing program if you need
an example.
I have some evergreens here that survive (though certainly
don’t flourish) and set seeds well, but their seedlings have very poor survivability through the winter in my environment. Those few that make it through though are
often well worth the effort and usually continue to show hardiness. A technique
I have found that is giving me some success is to use the pollen of these more
tender evergreens on hard dormants that are very cold hardy to produce
seedlings that seem to survive more frequently. Often all the seedlings are
somewhere in the semi-evergreen category, but they may be more hardy and can
often throw dormant offspring when backcrossed to other dormants.
I have no peer reviewed proof on this technique, and so far this is
only my anecdotal experience, but it seems that when I take one of these more
tender cultivar's pollen over a very hardy dormant as pod parent, I get better survival rates in the
seedlings than I do if I make the reverse (reciprocal) cross. This may not
prove to be true in all cases, but so far, this seems to be the most successful
route in getting hardier seedlings from these more tender cultivars in my
breeding program.
Now I want to turn to another aspect of foliage type. It is
important to remember, especially for beginners, that all plants registered as
a given foliage type may not always be that foliage type. Sometimes it is that
a cultivar performs differently in your garden than it did in the hybridizer’s
garden. Sometimes a seedling gets labeled wrong or information gets mixed up in
the registration process. I don’t like to think that anyone is intentionally
falsifying foliage habit for whatever advantage they may assume they get from doing
that, but it is not outside the realm of possibility I suppose. I never assume
that is the case though as I always give people the benefit of the doubt.
An interesting example - the cultivar on the right is a registered dormant, while the cultivar in the center is a registered semi-evergreen and the cultivar on the left is a registered evergreen. Can you tell any significant difference between any of them? I can't either... To me, these are all three in the 'semi-evergreen' category, with none being true dormants or true evergreens in my garden.
It is important to remember that there are species that are
evergreen in warm winters and dormant in cold winters, and there are cultivars that perform in the same manner. When this happens, it is
usually a happy surprise for all concerned, as such a plant registered as
dormant by a northern breeder may prove to be evergreen in the south and
vice-versa. More often it occurs that plants registered as semi-evergreen or
evergreen by a southern breeder may turn out to go dormant when grown in the
north. Both Linda Sierra and Priscilla’s Rainbow are examples of semi-evergreen
and evergreen cultivars that go dormant in the north.
Priscilla's Rainbow - a registered evergreen that, as you can clearly see, goes dormant in my garden. This one is well known to go dormant in cold climates, but remains evergreen in warm climates. It has very tight resting buds that are mostly underground throughout the winter.
Another registered evergreen that goes dormant in colder climates, Challenger is a Stout cultivar from 1949 that is a blending of H. altissima and H. fulva, both of which show this type of foliage habit being evergreen in warm climates and dormant in cold climates.
What can be less exciting and desirable is when you purchase
a ‘dormant’ only to have it prove to be some form of evergreen/semi-evergreen
in your garden, if you really wanted a dormant (and I can assume the opposite
would be true if you wanted an evergreen, but got a dormant instead). I have heard discussion that there are two types of dormancy - one is
alleged to be temperature-triggered dormancy and the other is alleged to be
light-triggered dormancy. If this is the case (and there is no solid proof that
I know of that it is), perhaps the triggers for dormancy are very different in various
areas and so something that goes dormant in one area may not get the right
trigger to go dormant in another area. I can’t say, but I don’t want to think
people are too fast-and-loose with their observations of the foliage habits of their introductions.
A situation that does raise my eyebrows a bit is when I
receive a ‘dormant’ from a breeder in a very similar climate or not too far
from me, only to have it remain green here through the winter. Maybe I am just
enough further south of the grower, enough warmer, to not trigger full
dormancy? I hope that is all it is. I also suspect that some growers have
looser definitions of what a dormant is than I do. For me, if there is any
green foliage still present during winter, then I don’t consider it a true
dormant. One grower sent me a ‘dormant’ that remained fully green all winter,
with foliage identical throughout the winter to Great White (an evergreen), which grew directly
beside it. That was ok as it was fully hardy and bloomed late enough not to
have any problems. I asked the breeder about this and the reply was, “Oh, yes,
it remains green, but its leaves don’t grow at all in the winter and it shows resting buds, so it is a
dormant.”
While it is true that the H. fulva clone Chengtu shows leaves that remain green through cold winters yet develops resting buds, the cultivar I am referring to did not show what I would call resting buds, any more than did Great White, growing beside it. If it was a dormant then so was Great White. None of the evergreens growing here in a normal or
hard winter grow new leaves (unless we have an occasional warm spell out of season) and a great many of them don’t have nearly as much green foliage
above ground as this ‘dormant’ did. Further, it doesn't match the AHS registration definition of a dormant. I don’t grow this one any more because it
turned out to be extremely susceptible to rust, but the foliage habit would not
have been any deterrent to me buying or using the plant.
Center - a registered 'dormant' that is one of the most evergreen cultivars I am currently growing...
Foliage habit seems to be a continuum, moving from the true,
hard dormant all the way to the true evergreen, with a range of variations
in-between. For me, and based on the AHS definition of a dormant, it is only
those cultivars that go fully dormant that are true dormants. However, there
are cultivars that are probably genetically dormant while also having some
small amount of modifier genes from evergreen ancestors and are close to the
true, hard dormant on the continuum, but don’t express as true, hard dormants
in many (most?) environments. These may be what some refer to as ‘semi-dormant’
and to me should be registered as semi-evergreens, rather than dormants, but it
seems these frequently get registered as ‘dormant’. When I walk through my
garden in the winter, I observe a good many registered ‘dormants’ with a bit of
foliage sticking up out of the dead leaves. These are not the resting buds of true
dormants, but are small fans with obvious leaves, even though they may be quite
small.
Another problem is that in the far north, cultivars will go
fully dormant that won’t even this far south, and may be full evergreen in the
near tropical south. I always try to bear these many environmentally influenced
variations in mind, as I don’t want to think badly of anyone or think anyone is
being deceptive, and while that may make me have my head in the sand, it allows
me to just shrug it off and move forward. After all, as a breeder, I can always
work toward the foliage habit I want in my garden, in my own program.
Another thing that I sometimes hear, but have not observed personally,
is there being any direct correlation between foliage habit and foliage
quality. I have seen beautiful blue-green foliage on all foliage habits, and I
have seen sickly, ugly foliage on all foliage habits. These variations in
foliage color/quality seem to have nothing to do with foliage habit and are
likely genes separate from the genes controlling foliage habit.
One final point that I want to touch on concerns foliage
habit and rust resistance/susceptibility. I have been told by several northern
breeders that their cultivars are ‘likely resistant, because they are good hard
dormants”, the implication being that only evergreens are rust susceptible.
This is absolutely false. There is absolutely no linkage what so ever between
foliage habit and rust susceptibility/resistance. I have cultivars of all
foliage types that show strong rust resistance, and I have cultivars of all
foliage types that show rust susceptibility. I can assure you that foliage habit
has nothing to do with this and neither does foliage color or
cold-hardiness/tenderness. The genes of resistance/susceptibility are not the
same genes as those that determine foliage traits.
I will say that I actually have more highly resistant
evergreen and semi-evergreen cultivars than I do resistant dormant cultivars.
Again, this has nothing to do with foliage habit. I suspect this is because
breeders in the south have had to contend with rust now for over a decade and so
they have been able to evaluate cultivars for resistance (so there is some information
on these available) and some few breeders in the south have actually been
breeding for rust resistance now for a good long while. Conversely, cultivars
in the north are not being evaluated for rust resistance with any frequency nor
is much selection for rust resistance being done in the north.
In defense of northern breeders, this is understandable, as
they don’t have the conditions to evaluate for rust, but it does mean that
northern cultivars are thus an unknown quantity in this regard. So my experience
points to there possibly being more susceptibility amongst many hardy, northern
dormant lines by default, than there is amongst some of the lineages (but certainly
not all!) of southern-bred evergreens and semi-evergreens, but this has nothing
to do with foliage habit and rather is caused by environmental constraints and
chance.
In closing, I would like to encourage people to talk about
the subject of foliage habit. I know some people get offended, but these things
are just facts. We in colder climates don’t say that some evergreens do poorly,
or don’t perform to their full potential, to offend people. Dormancy is not a
marketing scam (I have actually been told that!), nor is it an attempt to
vilify those breeding evergreens. Every foliage type is important and
necessary. Not every plant will prosper in every garden. This is a simple fact
of life. Sometimes that is related to their foliage type/cold hardiness, and
sometimes it isn’t. When someone in the north relates that a given
southern-bred cultivar has done poorly in his or her garden, being harmed or
killed in the winter, this is not an attack on the breeder of that plant. If I
introduce a hard dormant and a southern grower buys it and it dies, quickly or
gradually, I know that many hard dormants often don’t survive in warm areas, so
I can’t take that personally. Why should the reverse situation be any any different?
I fully understand why southern breeders focus on
evergreen/semi-evergreen foliage and I understand why northerners tend to focus
more toward dormants. I don’t in any way blame southern growers for growing and
breeding the foliage that works best for them. Why on earth would they not? I
grow and breed what works best in my garden, as should everyone else. Further,
it seems intuitively obvious to me that no southern breeder can know beyond a
shadow of a doubt how any of their introductions will behave in cold climates
until they have actually been grown in cold climates in many parts of the
continent, and they should be aware that there are instances where a plant is
hardier in the far north with constant snow cover all winter than they might be
in less cold areas where there is not a constant snow cover and where
temperatures can fluctuate a great deal. Conversely, the same can be said for
any plant bred in the north in regards to its ability to survive and flourish in the south.
It is only by exchanging information and our experiences
that we can start to gather a broad base of information to help people in
making proper cultivar choices for their area. I would think this would be
important to all of us, because successful gardeners are probably going to stay
with it longer than people who constantly have failures due to poor cultivar
choices for their area. I hope that this post can help to generate a civil and
friendly discussion and that we can share our information and experiences
without hurt feelings or angry responses and through that sharing only improve
our understanding of, and success with, our beloved daylilies.
