Rebloom

General Discussion
1

Quite often we read in catalogues terms as continual flowering, repeat flowering, reblooming, and even ‘occasional’ flowers later in the season.

How is this variety of different types of rebloom explained? Especially the ‘occasional rebloom later in the season’?

We have all learned that the reblooming qualities came with the genes of the china roses, and this is very much true but there might be other genes that are responsible for rebloom or genes that prevent a quick rebloom.

What are your views on this subject? And is reblooming really a 100% recessive trait?

2

Occasional rebloom may well be buds that remained dormant in the first flush. Up the street there is an enormous, unpruned Dr. Huey which has occasional rebloom in mid to late summer in some years. I investigated and it appears to be later shoots are coming from further down the main canes that the early flush. Unless the rebloom is coming on new wood of the season that is the more likely explanation. Fall bloom in old style shrubs for instance hybrid perpetuals on new wood often comes after some enforced dormancy like drought in mid-summer. For about 3 decades I had a seedling of the climbing sport of Crimson Glory. It never sent forth flowering canes like New Dawn but in some fall seasons it produced a few flowers, on the new matured canes. Many climbing sports of HT behave like that, blooming almost exclusively on old wood, and often not reblooming very well even if they carry remontant genes. Climbing Peace behaves that way around here. When cold winters freeze back the canes it blooms scarcely at all. By contrast in Philadelphia where it doesn’t get frozen back, it does very well as a repeat-blooming climber. So the sales persons for nurseries hedge their bets and don’t exaggerate the blooming abilities too much.

3

As an outsider who reads obsessively but hasn’t actually done my own hybridizations, I have some thoughts. Please feel free to correct any based on your own personal experiences.

  1. Garden roses are, overwhelmingly, hybrids involving multiple species, which don’t necessarily bloom at the same times. As such, “rebloom” in some hybrids may not be an expression of “China rebloom” but rather an incomplete suppression of singular bloom that occurs late in the season for one wild ancestor. Right away I think of Ramblers that originated from crosses between reblooming Teas/Chinas and R. wichur(ai)na (or R. luciae, whichever is the currently accepted name). The pure species blooms later, and I wonder if those diploid F1 Wichurana Ramblers with some repeat are really just showing the R. wichurana late bloom which isn’t interrupted because one recessive reblooming mutation doesn’t block that. Similarly, ‘Champney’s Pink Cluster’ has a long bloom because the repeat-blooming ‘Old Blush’ parent didn’t suppress initiation of bloom later in the season, as is typical for R. moschata. Interestingly, the triploid Wichurana Ramblers derived from the other parent being a tetraploid Bourbon, Hybrid Perpetual, or Hybrid Tea don’t seem to as commonly (based on what I read) present some later blooms. Perhaps two copies of “non-Wichurana” is enough to suppress one “Wichurana late-bloom” in triploids.

  2. I think, perhaps, that China rebloom isn’t a simple Mendelian recessive trait, but perhaps is something dose-dependent, especially in tetraploid roses. This, perhaps, explains why some of the old Hybrid Perpetuals were shy of rebloom – perhaps they carried 3 copies of “China Rebloom” rather than 4, which was enough to sneak through a little, but not enough to completely suppress “not blooming again.”

  3. I think some species are easier to “nudge” into reblooming than others. From what I’ve read of R. spinosissima, it seems easily nudged. Perhaps these species are native to rather austere conditions, and a rich environment (i.e. an influx of nutrients) is enough to initiate some bloom. From what I recall, R. spinosissima includes forms that live on sand dunes, and perhaps it evolved to bloom in response to nutrients required to “carry seeds to term” that may come erratically rather than seasonally.

  4. If the above ideas are true, that could mean that some garden roses including ancestry from late-blooming and easy-to-nudge species would require lower doses of China Rebloom to bloom again.

  5. There is at least one other rebloom factor out there in the genepool of garden roses – that which arose in ‘Autumn Damask’ and subsequent Damask Perpetuals, probably derived from R. fedtschenkoana, possibly supplemented by whatever causes R. moschata to bloom as it does. This could mean that a rose with rebloom factors from both Chinas and Damask Perpetuals may rebloom, despite being homozygous for neither, because that results in an “easily-nudged condition”, but offspring from those roses could easily be once-blooming as a result of independent assortment.

  6. Polyploid roses that aren’t homozygous for China Rebloom may have a spontaneous epigenetic mutation which results in the “silencing” (to some degree, if not completely) of a “wild-type” non-reblooming allele. This may be what happened with ‘New Dawn’ sporting from ‘Dr. W. Van Fleet’. Based on published ancestry, triploid ‘Dr. W. Van Fleet’ likely had 2 copies of China Rebloom and one “wild-type” Wichurana “non-rebloom”. As I mentioned in #1 above, this may have been enough to suppress “Wichurana late-bloom” since it was only 1/3 of the genome, but if a heritable epigenetic mutation occurred which “silenced” whatever interfered with rebloom, that could explain not only its rebloom, but also that its offspring rebloomed.

  7. Then again, as Larry said before me, perhaps the “surprise rebloom” noticed in some roses is actually really just a continuation of the first flush, but interrupted by Summer heat or some other change in conditions, which became “un-interrupted” when cooler and wetter conditions returned in late Summer or early Autumn.


    Again, these are just some thoughts, shared to engender further discussion. If anything I “thought out-loud” above is incorrect, please correct me.

:slight_smile:

~Christopher

4

Oh, and one other thing – there’s something different about how Chinas, Teas, Noisettes, and Polyanthas rebloom. I think there’s an “additional factor” that results in new growth from below a bloom cluster to “need” fewer nodes to initiate a new bloom at the end. My other reblooming old roses seem to want to push out growth that finishes at more substantial sizes before terminating in bloom. To encourage more of this growth, they typically need to be pruned a bit more after each flush. But the old types I mentioned above don’t – they’ll rebloom fast without pruning back, sometimes without even dead-heading. I don’t know if I’m explaining this well, but I think it explains how some roses will always seem to have a few blooms, while others bloom in flushes. The former need fewer nodes per new growth to signal formation of flower buds than the latter.

:slight_smile:

~Christopher

5

All flowering occurs once the appropriate wood experiences the appropriate heat/cold, light/darkness and can draw upon the necessary water and nutrients. Here, Banksiae and Laevigata “repeat”, and in some cases, virtually “flower continuously”. And, it is all climate induced. Mine aren’t flowering at the moment, but the ones in town along the freeway in full sun with a lot of reflected, radiated heat from the roadway, are flowering themselves silly, now we’ve had a bit of rain and no real “summer”, nor “winter”. They spent just a few weeks without any flowers, until we had a rain. Basye’s Amphidiploid 86-3 (Banksiae X Laevigata) is beginning to flower in the yard. Teas are also flowering well, while the few “moderns” in the yard are not. Teas don’t require the heat levels HTs and floribundas do to flower. Huey will often rebloom here and usually from wood which had previously flowered. The same occurs with my Hugonis hybrids (I no longer have R. Hugonis itself) and Xanthina, while Primula appears to want to “rebloom” from newer shoots. I.X.L and Veilchenblau “repeat” here fairly regularly, even when the “moderns” aren’t flowering. The right genes are required, but climate can, and often does, cause them to do what we don’t expect.

6

Mrs Scott (1939) discussed remontant bloom in climbers. In several of the cases, the later bloom arose from shoots growing out of (or just below) the previous inflorescence. This sort of repeat bloom also occurs in some irises. A second flowering stalk grows up from a vegetative bud below the first stalk.
http://bulbnrose.x10.mx/Roses/breeding/ScottClimbers1939.html

Repeat blooming occurs spontaneously in some varieties, but must be forced in others. Penzance found that most of his Sweet Briar hybrids would bloom again if the partially ripened hips from the first flowering were removed. Kim Rupert reports the same phenomenon in ‘Schoener’s Nutkana’.

Is ‘Marechal Niel’ everblooming? The reports vary. In one article I read, the plants were forced to bloom once a year, in order to get all the blooms at the same time – for the cut-flower trade. Otherwise, it seems to mingle everbloom with repeat bloom, something like ‘Gloire de Dijon’. However, ‘Marechal Niel’ has been the parent of some strictly everblooming, bushy varieties that are classified as Teas despite the Noisette ancestry.

There appears to be a lot of Noisette ancestry concealed within the the HT and Floribunda classes. E.g., ‘Lady Mary Fitzwilliam’ was raised from ‘Devoniensis’, which was a seedling from ‘Smith’s Yellow Noisette’. The behavior of some climbing HTs suggests that the repeat blooming habit of the Noisettes is popping up from time to time.

It has too often been assumed that all climbing sports involve gene mutations, but this is not necessarily the case. Here are two notes on the ‘Climbing Devoniensis’.

The Journal of Horticulture, Cottage Gardener, and Country Gentleman pp. 152-153 (Feb 21, 1865)
CLIMBING DEVONIENSIS ROSE.
S. J. Pavitt, Rose Cottage, Bathwick, Bath.
In the year 1857 I budded some of the old Devoniensis on the Celine stock, when on the following year many of the plants made shoots from 3 feet to 9 feet in length. I have now in my stock one of the original plants I obtain my buds from, it having withstood the severe winter of 1860-61.
Origin of Cl. Devoniensis (1865)



Journal of Horticulture and Practical Gardening, 9(237): 94 (Aug 1, 1865)
CLIMBING DEVONIENSIS ROSE.
Mr. Rivers states, “… The climbing Devoniensis reverts to its normal condition if buds or cuttings are taken from the blooming shoots.”
Untitled Document

The Brownells’ once-blooming ‘Copper Glow’ sported to the everblooming (?) ‘Orange Everglow’. The latter can revert entirely to the former if the more vigorous, once-blooming canes are not cut out.

American Rose Magazine 5(9):185-186 (May-June 1944)
What is an “Everblooming” Climber?
The Brownells,
Little Compton, Rhode Island

While the rose hybridizer cannot successfully combine the true reblooming quality with the ordinary cane-growth of climbers, very satisfactory types may be produced by encouraging the vigorous branching growth of the flowering stems. An illustration of this is the variety Orange Everglow in which these two types of blooming habit are present and segregated. Certain confirmation lies in the fact that if the once-blooming cane-growth is not removed it may by its vigor smother and prevent the establishment of reblooming wood.

‘Gloire des Rosomanes’ is another one that can’t quite decide whether to be short and free-blooming, or tall and less free.

The Cottage Gardener 5: 381-382 (Mar 20, 1851) ROSES FOR FLOWER-BEDS
Donald Beaton
No one seems to like > Gloire de Rosamene> for a bed; but by a particular management it makes a splendid bedder, indeed the very richest of all the roses. For bedding, this rose should be treated as a biennial, and no more; that is, to put in cuttings of it every year in April (they will root anywhere, if you stick them firm in the ground), and to plant them in the flower-bed next March, or whenever the bed is ready for them in the spring. Then, from the first of June to the end of August, every shoot which looks very strong, and is likely to run away with the sap, as gardeners say, must be stopped when it is six inches long. In this way all the shoots over a whole bed need not differ much in strength, and they will not stop from flowering in July or August, as this rose is apt to do when older plants are used. After the beds have done flowering in December, the plants must be disposed of, for all the gardeners in the country could not make a regular bed of them the second season, if the soil was ever so poor, and I do not think there is a rose known that will do better in the very poorest soil than this; and it would grow in rotten dung without any soil at all; it is no matter, therefore, for this rose where you plant it > as a biennial.> On thin sandy soil the plants should stand at six inches apart every way, or even thicker, and nine inches between plant and plant will not be too thick for a good bed of the richest soil, that is on the understanding that the same plants are only to flower one year on the same bed. A border of the old white China, planted round a bed of > Gloire de Rosamene> , thus managed, is the very best combination of rose colours I know of; and in a mild autumn both will go on flowering down to the end of November, and I have had them in good bud for bouquets in Christmas week.
Beaton: Bedding Roses (1851)

7

Again, climate. Marechal Niel flowers almost year round here. Gloire des Rosomanes literally flowers twelve months of the year right here, and will flower on recently rooted cuttings as well as huge, old plants which receive no pruning. If pruned like a modern, it stops flowering until it has produced the necessary new growth to start it all over again.

8

Kim,
‘Marechal Niel’ seems to needs its wood “ripened” before it can bloom. This behavior has been reported for some other Tea-Noisettes. And so …

Journal of Horticulture and Cottage Gardener 20: 469 (June 5, 1890)
Maréchal Niel Rose
J. B. JONES
In the early part of 1884 we did away with one of our vineries (30 feet by 18 feet), and in January, 1885, we planted five > Maréchal Niels > and one > Fortune’s Yellow> ; the former were budded on Briars, the buds being then in a dormant state. That season each bud produced 60 to 80 feet of wood, the result being we cut nearly 700 blooms from them. After they had finished flowering I cut them back to one eye. So well did this system act I have ever since adopted this plan, with such marked results that I shall ever continue it. We have this year cut over 2000 blooms. They are trained and tied to wire 14 inches from the glass; the annual shoots make from 20 to 25 feet, and 3 or 4 inches apart; the size of wood vary from 1 to 2 inches in circumference.

If I’m reading this correctly, the canes had to regrow from the ground (nearly) and ripen before the profusion of blooms arrived. Two thousand blooms on five plants is a pretty impressive accomplishment. And profitable, I’m guessing.

As for ‘Gloire des Rosomanes’, the oddness of it is that it produces some canes that try to grow tall, while others are shorter and more inclined to bloom sooner rather than later. After the plants get established, it can be virtually impossible (according to Beaton) to maintain them as dwarfs suitable for bedding. And even when he used them for hedges, he whacked the bushes to the ground every other year. That is, odd numbered plants were whacked one year, even numbered plants the next. In this way he had a veritable flower factory.

BTW, the practice of “whacking” may be worth another look.

American Rose Magazine 1(17): 10-12 (Sept-Oct 1935)
To Whack or Not to Whack
DR. J. H. NICOLAS
It is an acknowledged fact that roses, shrubs, and trees grow more vigorously and develop a greater leaf-surface when pruned. European people are more rose-minded than we are—and grow better roses than most of us—and their pruning is more radical than I recommended in my Manual. Here is an instance that will interest Portland: The most beautiful planting of Mme. Caroline Testout (250 plants) I have ever seen was last summer in a large estate near Bruxelles, Belgium. They were the original plants received from Pernet in 1894, but were pruned to the ground each year so that not even the stubs showed. I dug around one plant; the stool was at least six inches in diameter and the main root-stalk four inches in diameter! Perhaps if that same treatment had been applied at Portland, Caroline would not have petered out!
Nicholas: Rose Whacking (1935)



House & Garden 55: 90-91, 194, 206, 208 (June 1929)
THE RENAISSANCE OF THE HYBRID PERPETUAL
J. H. NICOLAS
Last summer it was my good fortune to visit Monsieur Cochet, the fifth generation of the great Cochet dynasty of Rose hybridizers and scientists (Cochet the First helped Empress Josephine in establishing her historical Roserie at Malmaison) at his estate of Coubert, about thirty-five miles west of Paris. He took me around to see great fields of Roses grown for the cut flower market of Paris. In that immediate vicinity are over 750 acres owned by 160 independent owners with a selling organization. They grow Hybrid Perpetuals only, and on August 3rd they were still cutting large quantities of Roses as beautiful and perfect as any grown here under glass — and this had been going on daily since the middle of May.

Walking through those fields, I was surprised to see what I thought to be young maidens (first year growth from buds inserted the previous summer). When I asked one of the owners whether these were new plants, he said to my amazement, “This field was planted by my grandfather thirty years ago and but very few plants had to be replaced.” Calling one of the working men, he had him dig around a plant and then I saw a stump several inches in diameter! He explained that each year, in the middle of March, the plants are “mowed” close to the ground; they then grow many new stems three or more feet long ending with splendid flowers; the stems, two eyes below the cuts again sending flower-bearing long stems. I commented on the absence of those long sterile suckers we generally see on Hybrid Perpetuals in midsummer, and my host replied, “The plants are kept too busy blooming to waste their energy on suckers”.

This particular field was of Ulrich Brunner. Other varieties doing splendidly and “perpetually” under the same treatment were: American Beauty, Baroness Rothschild, Captain Christy, Duchess of Sutherland, Georg Arends, George Dickson, Gloire de Paris, Mrs. John Laing, Suzanne Marie Rodoconachi, Triomphe de Caen, Vick’s Caprice, Victor Verdier. Among the newer ones, Henry Nevard, John Russell, S. M. Gustave V. and Mme. Albert Barbier. I was also told that budded plants only respond to such treatment.
Nicolas: Renaissance of the Hybrid Perpetual (1929)

9

I happened upon this note just this evening. Thought it might be of interest.

RHA Newsketer 6(2): 5-6 (Summer 1975)
Breeding for Yellow
Bernard C. Gardner, Los Banos, California
“For too long a time I tried using R. Foetida as a pollen parent, in the hope of getting that unfading deep yellow color in a better rose. The seedlings always tuned out to be pale yellow or white. Quite unexpectedly, however, they were continuously flowering.”

There are other examples of rebloomers turning up in the F1, including Pernet’s. Despite the report that ‘Soleil d’Or’ was raised from Antoine Ducher x Persian Yellow, some writers have claimed that it must be two generations removed from ‘Persian Yellow’, possibly helped along by a Hybrid Tea. They present no evidence, but only vaguely mention Mendel.

10

Thank you for that, Karl. Barney was a gracious gentleman. I had the pleasure of knowing him the last few years of his life. I miss him.

11

Reblooming in roses is definitely not simple and straight forward. I do not know the science behind it but from observation of seedling and species plants I have seen non-remontant seedlings coming from 2 fully remontant parents (‘Gold Medal’ seemed to produce a fair amount of non-reblooming seedlings) and more recently from clones of Rosa acicularis that I obtained from my childhood home in Fairbanks, Alaska, I have seen the production of very late (and ugly) blooms on new wood. In the later case, I suspect that the R acicularis clones were confused by our long hot summer and “thought” they had already gone through another winter (they shut down during the summer) and then tried to bloom again in the late summer.

With regard to the variations in “reblooming” seen among remontant roses, there are the “on and off again” rose types with a clear and sometimes prolonged delay between flowering, to the virtually continuous flowering types that bloom all summer long. Among modern roses, one can find the full spectrum between these two extremes. It seems that the remontant type roses that exhibit a profusion of bloom in the spring, tend to be more likely to have clear cycling of blooming times (and later cycles are never as profuse as the spring bloom). The more continuous flowering types seem to have a more modest spring flush, but then continue flowering.

Another component that affects the sheer number of blooms is the actual mass of the flowering - roses with smaller, more lightly petalled roses produce more blooms, while the larger, heavily petalled types produce far fewer blooms. This is a generality though because there are definitely the super performing, floriferous beauties that we all strive to produce. Selecting overall floriferousness as an important trait in parent plants may increase the opportunity to see the real powerhouse flowering machines among our seedlings.

12

I know I’ve said this before, but it’s still kind of a new revelation to me. (in response the last paragraph of the previous post)

If a rose’s blossoms last two days instead of one, it needs to produce only half the number of blossoms to have the same amount of color on the plant at any given time. If the blossoms last three days, then it only needs to have 1/3 the blooms. It seems like this petal longevity would take less additional energy to produce than actually making new blossoms. Therefore it seems like petal longevity is an important characteristic to breed for, especially for those of us messing with species roses. Once remontancy is regained, blossom longevity will make a vast difference in overall color impact.

Another way to game the system is what Peppermint Pop does…its center petals kind of stick together to make it appear more double than it is. Therefore it can have the bloom power of a single rose while appearing double.

13

Points well taken. Longevity is also very temperature dependent among roses that last more than 1 day, in my experience. This is a characteristic that the knockout roses have, perhaps in excess. In our climate Rainbow KO will hold petals until they turn green and brown making some preddy ragged looking bushes at midsummer. Fortunately, crosses to roses that tend to drop too fast usually gives something in between the two, not just all or nothing one way or the other which would be the case for simple inheritance of a strong dominant or recessive trait. Some of the drift roses hang on a bit too long also. Apricot drift and it’s yellow mutant do that along the street at the campus. Getting RKO traits into a mix with Soeur Therese + another rose has given me a couple intensely yellow roses that last about 3 days in hot weather and more like 10 days in the cool of autumn. If sufficiently winter hardy this may be a useful way forward but it will take a couple years to confirm that part. Good disease resistance too so far.

On the energy use front, I did some calculations several decades ago looking at Carefree Beauty flower production as amount of biomass. If you compare it to agronomic crops, it is very small. You could argue that for something like RKO, the petals block sunshine from reaching leaves and reduce photosynthesis. I don’t really buy that argument either. Even if you throw in the total dry weight of hips produced by a highly fertile rose like CB, it is very small compared to soybeans or wheat where the harvest index is around 50 %, and in the tons per acre range for a cold or short growing season. Of course perennials are different from annuals with monocarpic senescence. The Land Institute (Salina KS) is aiming for perennials that yield half as much as annuals. So I think we have a very long way to go with roses, and it’s all driven by hormones, and perhaps the time taken for differentiation of one kind of tissue to another. RKO is pretty good at making very short flower stems so it may be going in the right direction.

We ought to be able to get something that lasts like zinnia or marigold, though maybe the composite flower is a cheat. But consider petunias or dwarf snapdragons for flower production or longevity and see where the arithmetic comes out

Merry Christmas. And good breeding in the new year.

14

Thanks, Larry, and to you and the rest of the “gang”, too!

15

I wanted to mention this case. I wrote to a friend about it back in 2001, but I can’t remember where I read it. Anyone remember it?

Franc Holliger (Canadian amateur rose breeder) crossed the hexaploid > Rosa nutkana > with a diploid China rose. One of the tetraploid offspring rebloomed, and was reasonably fertile.

16

Dr. Fabrice Foucher and his team have done a lot of great work understanding flowering in roses and also associated species like strawberries. Here is a link to one of their papers

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1365-313X.2011.04776.x

There is a key general gene found in many plants called Terminal Flowering Locus (TFL) that basically suppresses flowering, except during specific times of the year and situations when the gene’s expression is very low- like our one time blooming roses in early spring. The gene after flower initiation again is normally expressed and flowering is inhibited (producing messenger RNA and ultimately a product that suppresses flower initiation).

There are segments of DNA that move around the genome called transposons (trans=across; poson=position). Barbara McClintock described this first in Indian corn and the flecking on the kernels and she later on a Nobel Peace prize. Transposons are found in animals and other life forms too. They can land and become inserted in a functional gene and mess it up. That is basically what has been described as happening in our reblooming roses and their TFL gene (called RoKSN in this paper to commemorate previous understanding). The messed up version of the gene is recessive and does not produce viable messenger RNA. If the rose is recessive for all copies of this gene containing the transposon DNA within it, inhibition of flowering from the TFL gene is not happening and the rose reblooms (CF= continuously flowering is the term in their paper). It is like this rose is perpetually in early spring without this gene expressing to stop flowering. Once Flowering (OF) is the wild type version of the gene that flowers just seasonally as described in their paper. Transposons periodically can transpose or move. This can be very rare, or sometimes in some other examples, in certain tissues and growth and development stages, occur frequently. Likely, this transposon in the TFL gene doesn’t jump out of the gene very often. For striped roses, it seems like there is a transposon in a pigment gene (anthocyanin gene) and it is triggered to jump out in some petal cells at a certain stage of development. Cells continue to divide after that point to make the rest of the petal tissue. The cells and tissue that continue to divide from a cell with the transposon still in place produce no to very little anthocyanin pigment, and the cells and tissue where it jumped out once again produce anthocyanin and those cells and tissue look pink/red/purple. A transposon landing in a pigment gene in corn kernels is how Dr. McClintock first identified transposons.

Sometimes in continuously flowering roses we get climbing sports. The transposon gets cut out and the gene functions again relatively normally in terms of its suppression of flowering and the rose grows long canes throughout the growing season after the initial bloom. Sometimes though, the excision of that DNA segment of the transposon is not complete and it leaves some portion of itself (long terminal repeat). This little bit of material left in the gene can lead to the gene actually being expressed it seems, but to a lesser degree with lesser inhibition of flowering. Climbing Peace from this paper falls into this category.

I suspect this key gene plays the major role in flowering of our roses and the variations we see. The range of variation in flowering may be due to the variations of the alleles of this gene and how this gene interacts with environmental conditions and for alleles that can be expressed to produce messenger RNA, when the expression is reduced to promote flowering. It would be interesting to sequence the variations of this gene there are in some of the roses we may be interested in understanding more about in terms of their flowering behavior. Fabrice’s team has done this to some extent. They learned that they can find differences in where a transposon landed/its sequence in ‘Old Blush’ versus rugosas versus repeat flowering R. multiflora (I assume what led to the multiflora based polyanthas). It seems evident from their research that transposons landing in this key gene occurred in multiple rose species over time leading to the repeat blooming variants. There isn’t necessarily one event that led to the recessive repeat bloom variation and all other species and cultivars that repeat are descended from it. That seems to be the story shared in some older rose literature that all repeat bloomers somehow descend from Rosa chinensis spontanea. In nature, however, the trait hasn’t been favorable generally and for the most part seems to have not become the norm. It seems though for Rosa rugosa it has taken hold across the species. They do ripen hips relatively fast though and can make it work to their advantage it seems. I’d love to see what can be learned by sequencing this gene in the more reblooming versions of R. arkansana. It would be interesting to do some expression studies of this gene too at different times of the year in different climates to see what patterns/triggers can be identified. It is interesting to do expression studies in a climate like Kim’s in CA where some roses that are once blooming elsewhere bloom again after a summer stress with heat and drought.

I’ve seen/heard about one time blooming variants of both ‘The Fairy’ and ‘Sea Foam’ that were unfortunate mistakes. At different liner nurseries (they sell just young rooted cuttings) they kept taking cuttings of the one time bloomers because they made more cuttings (because they weren’t blooming). Customers were disappointed their plants didn’t rebloom…

Maybe there is something to a dose effect proposed with some of these more intermediate alleles with a portion of the transposon left behind?

17

Here is a link to a pdf from a talk Fabrice and his group put together on this work. https://colloque.inra.fr/rgc8/content/download/3928/44877/version/1/file/RGC8-S3O05_F.%20Foucher.pdf

18

David wrote, "It is interesting to do expression studies in a climate like Kim’s in CA where some roses that are once blooming elsewhere bloom again after a summer stress with heat and drought. " Most don’t require the heat/drought episode to “repeat”, David. Here, they just rebloom as if it is “normal”. It’s QUITE neat!

19

Hi Kim! That’s fascinating!! I wonder what environmental cues are allowing for the reliable rebloom. What an amazing climate you live in!

20

We usually don’t get “summer heat” until very late, late September to sometimes as late as early November. Much of the California coast is like that. When I worked in Pacific Palisades, we had budded, canned plants of Harkness’ Nigel Hawthorne, the Hulthemia hybrid, which flowered from March through October. Many “once flowering” types simply do it. Banksiae and Fortuniana are almost all “summer” flowering. Those on the freeway here in town are still flowering! We usually get about 700 chill hours annually, so we can grow a wide variety of things and “spring” starts early and often lasts until nearly late September. We may have some heat spikes from August forward, but it often drops back into the coastal cool weather. Our “average temperature” is 75 F. That’s a HUGE reason I live here!