A meeting place for rose breeders.
david zlesak
Posts: 334
Joined: Tue Nov 26, 2013 12:27 pm

Re: Rebloom

Post: # 68855Post david zlesak
Sat Dec 29, 2018 11:00 am

It sounds wonderful Kim! Hmmm. I studied Easter lilies for my doctorate and aspects of flowering was a part of my thesis. Temperatures below 70F can be perceived as chilling to Easter lilies, even though if the temperatures are below 50F the chilling hours (high 30's best) can speed along the chilling requirement significantly. If lilies are below 70F at times and the days are long, Easter lilies can eventually flower. If temps are above 70F they seem to not flower. 70F is a critical temperature. What are your night temperatures? I wonder if consistent chilling being perceived, especially at night, lead to greater flowering and perhaps suppression of RoKSN. Perhaps the stray fall bloom in some roses in other areas is due in part to cooler temps at night starting.

Posts: 4875
Joined: Sun Dec 11, 2011 6:54 pm
Location: Zone 9b Central California, Sunset Zone 15

Re: Rebloom

Post: # 68856Post roseseek
Sat Dec 29, 2018 11:34 am

Wonderfully conveniently, the nearest Wunderground Weather Station is exactly next door to me. ... 7279999998 The next ten days, night temps are to range between 32 and 47 F while day temps are between 60 and 66 F. I actually is pretty wonderful! Believe it or not, the fields around us are still supplying strawberries, blue berries and black berries and the fields are already producing cut gladiolus flowers as well as the traditional kale, lettuce, broccoli, cabbage and Brussels Sprouts. The artichokes have finished and been replaced with the "cooler crops". We pretty much always have cool nights. A "hot night" is one which remains above the low to mid sixties.
California Central Coast
USDA Zone 9b
Sunset Zone 15
Cooler inland coastal valley with strong marine influence

Karl K
Posts: 1050
Joined: Sat Jun 02, 2012 4:49 pm

Re: Rebloom

Post: # 68862Post Karl K
Sun Dec 30, 2018 7:09 pm

AquaEyes wrote:
Fri Dec 07, 2018 10:05 pm
1) ... 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.
I have pictures of Rosa moschata flowering happily into October. ... chata.html
For many years, people thought that the once-blooming Rosa brunonii was the Musk Rose parent to the Champneyana roses. It was not.
The influence of the real R. moschata can be seen most clearly in the Tea-Noisettes. Each flower is borne on a very short lateral stem, rather than than at the end of every cane or shoot, as in the Teas and Chinas.
This is actually a dominant trait, as we learn from a few descendants of 'Marechal Niel', such as 'Souv. de Pierre Notting' that are bushy Teas with none of the Noisette climbing habit.
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.
There is another possibility that I call "Elective Expression", though it has picked up a few other names in the past couple of centuries. It is known that, sometimes, it is not always a matter of dominance when two alleles are brought together. It has been observed in corn (maize) that when two inbred lines are crossed in the same way, year after, the results are not always the same for a given locus. That is, the maternal allele is suppressed some years, the paternal allele silenced in others, and in still other years both alleles are expressed.

Most of these cases involved are hidden from sight, though they are still important. But the same principle has been observed many times over the years. For instance, when the Trifoliate orange (Poncirus trifoliata) is crossed with the common orange, some offspring are trifoliate, some are unifoliate, and some try to take an intermediate position. Hybrids of the Trifoliate orange with the lemon are even weirder. ... e1911.html

It is useful to consider that the pattern of silencing/expression that was establish in the seedling, is sometimes altered, especially when the plant is forced into embryogenesis, as occurs when an adventitious shoot emerges from a root. This may explain how the reblooming 'New Dawn' came up as a root-sport of the once-blooming 'Dr. W. Van Fleet'. ... wdawn.html
3) I think some species are easier to "nudge" into reblooming than others.
No doubt about it. Way back in 1825, Sarah Mackie listed the 'Scotch Perpetual'. No description, sadly, but at least we do have 'Doorenbos Selection'. However, I think the Damasks have the advantage.

I tried to learn when the "Autumn Damask" first came into existence. Eventually I ran into a wall: older writers were concerned with the medical virtues of plants, rather than with their gardening uses. Lobel and Pena (1571) wrote that garden roses are "also surprisingly fruitful, often twice-bearing, sometimes you may see thrice-flowering." No named varieties.

Ferrari (1633) mentioned only a Rosa "Italica flore pleno perpetua".

Then, in England, Austen (1657) wrote, "As for Rose-trees, some damask Roses, and some Provosts beare a second time, the same yeare, though but few, if cut soone after the first bearing in the full Moone. But besides there is a Rose-tree, called the Monthly Rose, which beares Roses untill the coldness of the winter stop it, about November.

I don't know how to dig further into this, but I will venture to guess that someone plucked hips, and was pleased to observe that some of the bushes opened another crop of flowers. Suckers and cuttings of these favored bushed will preserve the slight tendency to rebloom. And some of the seedlings from these plants may show the tendency more strongly.

And by the way, there was not just one "Autumn Damask". Loddiges (1820) listed the following:
71 portland
103 four seasons
165 blush monthly
264 red monthly 
276 bifera carnea 
280 white monthly 
569 pestana 
617 perpetuelle rouge vif 
660 tout les mois coeur gris

There was also a 'Striped Monthly' at the time, but Loddiges didn't mention it.

Karl K
Posts: 1050
Joined: Sat Jun 02, 2012 4:49 pm

Re: Rebloom

Post: # 69004Post Karl K
Thu Jan 17, 2019 4:32 pm

Another form of rebloom is what I have been calling repeat bloom. It occurs when the flower forming habit is imposed on buds, and even on branches, that are not ordinarily expected to bloom. I observed this on what I believe to be 'Paul's Scarlet Climber' that bloomed in four or five flushes in a year, but always on the laterals (or "spurs") that had already bloomed. The following year, more blooms appeared on the same laterals.

Much the same thing happens in some annuals, as Roberts (1948) discussed, that "do not revert to a vegetative growth cycle in a reversed environment, once they have come to flower and fruit."
After-Affect:—Another phenomenon which varies with the flowering habit of the species is the difference in reaction to a change in environment, after the plant has come to flower. Plants with a terminal flowering habit as Klondyke cosmos, poinsettia, Rudbeckia laciniata, Salvia (var. Harbinger), stock (Christmas Pink) and Maryland Mammoth tobacco can be readily changed to a vegetative state after they have come to flower by placing them in an environment which inhibits flowering, plants with a systemic flower forming habit as morning glory (var. Heavenly Blue), petunia (forcing), soybean (var. Biloxi), and Xanthium echinatum do not revert to a vegetative growth cycle in a reversed environment, once they have come to flower and fruit.

The continued flowering of an induced plant after being transferred to an environment unfavorable to flowering (provided it is of a species having a systemic blossoming habit) presents an interesting problem. The mechanism of the "after-affect” has been the subject of considerable theorizing. A possibility of an effective mechanism is presented by the fact that annual plants which show after-affects do not characteristically renew cambial activity once it has ceased at the time of induction and flowering (34). In this connection it must be kept in mind that plants which require a long period of treatment to establish a permanent after-affect will revert to a vegetative type and regenerate cambial activity if the induction treatment is discontinued before induction is completed. Terminally flowering varieties regenerate cambium whenever returned to an environment unfavorable to blossom induction. ... l1948.html
Repeat bloom, rather than everbloom, is also seen on some climbing roses. ... s1939.html

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