temperature effect on bloom form

This year we had a very cold spring with moderate to hard frosts interspersed with warmer spells from late Feb until late April. It was a cold winter too and Silver Moon lost a significant fraction of its long canes. With the cold weather delay it bloomed about a week later than usual. The most striking thing of all though is that all the blooms are very double, quartered, full of petaloids, and often turning into brown balls.

Has anyone else seen this? I know that S.M. is generally grown in warmer climates.

I just looked on HMF and for S.M. I see no photos or discussion of anything but a near single, large, pale yellow bud and white flower. I think that during bud development early on, before flowering shoots with the flower buds actually burst from the canes, repeated doubling occurred. Once-flowering roses, like edible berries such as blackberries, very likely initiate the flowering shoots and even flower buds, some time before new shoots are visible.

Two points in support of this. First, a cross of S.M. x Carefree sunshine, gives a very pale yellow fairly doubled repeat-blooming rose, generally quartered.
Second, some roses such as Crimson Glory turn nearly single in hot weather. The number of stamens vs petaloids in some others is also temperature dependent with the first flowers of the season giving little pollen relative to later ones.

Temperature also influences the number of buds per stem.

I recall a mention somewhere that the original Rose Edward produced too many buds in cold weather, and none of them opened.

It would be useful to know which varieties could be persuaded to make fewer petals under controlled conditions. I never could get ‘Alexander Hill Gray’ to set seed.

I never saw ‘Crimson Glory’ with so few petals it might be called single, but I did once see it with scalloped petals.

(June 27, 2000) ‘Ellen Willmott’ and ‘Mission Bells’ photographed the same day were similarly odd.

More info on temperature and growth/flowering.

A Manual of Gardening for Bengal and Upper India, pp. 475-477 (3rd edition) (1874)
Thomas Augustus Charles Firminger

  1. ROSE EDOUARD.—Originally from the Isle of Bourbon, and parent of the whole group. An old well-known Rose in all parts of India, most desirable for the constancy of its bloom as well as for the sweetness of its flowers; during the Cold season it produces flower-buds in unbounded profusion, which rot in the centre, and never open. The stems after blossoming should be pruned in closely. Exceedingly vigorous in growth, and easily propagated, affording the best stocks we have for budding other kinds upon.*
  • For the history of this rose see a paper sent by me to the journal of the Agri-Hort. Soc. vol. iv. part ii., N.S

    The Indian Gardener, Volume 1: 288 (July 7, 1885)
    B. S. H.
    Rose Edouard, a grand old Rose in itself, as regards habit, is better adapted as a stock for general propagation than the preceding [Rosa gigantea]; it has, however, one unfortunate defect, which it too frequently transmits to the plants worked on it, that is, that during the cold season it almost invariably refuses to expand its blooms.

It occurred to me this morning that I have another example of temperature affecting flower quality through the rootstock:

Gardening 10: 198-199 (Mar 15, 1902)
Hybrid Stocks for Rose Propagation
Walter Van Fleet

… Perle des Jardins, budded on an established plant of the Cherokee rose, Rosa laevigata, is giving splendid blooms of almost exhibition quality, in a cold, damp house where five years’ effort with potted Perles on own roots and Manetti only resulted in a chance “bullhead” once or twice a year. Further trials will be made with teas and hybrid teas on this stock.

I wonder how ‘Rose Edouard’ would perform when grafted to R. laevigata.

Interesting that there are so well-established examples of the temperature effect.

The two last flowers of the season on Silver Moon were almost normal. They have two rows regular petals, about 5 rows of petaloids with one yellow edge, lots of stamens displayed in an orderly way. These flowers appeared as the secondaries in a cluster of about 8, on the lowest (latest arising) floral shoot of a long cane. I would interpret that they initiated about May 1 when the weather flipped to warm. So today is near 6 weeks.

I looked for some other examples, but only came up with this:
At the SJ Heritage garden there were two plants identified as ‘Harison’s Yellow’. They were quite different (though similar). One flowered over a longer period. It may be ‘Williams’ Double Yellow’.in 2003 and 2006, both times following a heat wave, the yellow blooms were brushed with red, like McGredy’s “Hand Painted” roses.

Yes, I saw that color effect on late blooms in heat back around 1980-85. I wrote about it maybe in the old days paper Newsletter of that time, or possibly on this forum a decade or so ago… That’s why I assumed that the true parent was Austrian copper rather than Persian yellow. Now of course someone with ambition and primers can ID the DNA of the parental contributors. My HY came from Roses of Yesterday and Today in Watsonville? CA.

If van Fleet couldn’t get germination of seeds they must be really challenging. But perhaps taking off the achene coat will find a viable embryo.

I have a different take on the red pigment in Bicolor. I think red is suppressed in the Lutea form. The ancient mutation released pigment onto the surface of the petals.

Something similar happened with the Scotch roses. Among a batch of typical white-flowered wild plants, one bore flowers with a tinge of pink. Later generations turned up rose, red, and purple forms.

Viability of seeds is a puzzling matter. Prof. Allard raised seedlings from ‘Harison’s Yellow’ on several occasions.

It is worth noting that some of the HY seedlings had pink flowers. This is further evidence that the lack of red pigment on the petals of R. foetida lutea and R. spinosissima is due to a dominant non-red trait (suppression).

Dominant non-red is also seen in a cross raised by Mansuino (1960). “By crossing the seedling (R. banksiae lutescens x Tom Thumb) with the old Noisette Lamarque I have lately obtained a Banksiae type bearing beautiful deep rose colored flowers.” Both of the immediate parents were white tinged with yellow.

I remembered another example of dominant non-red:

American Rose Annual 45:114-118 (1960)
The Inheritance of Color in Hardy Roses
Percy H. Wright
Soon after my original cross, I put pollen of Harison’s Yellow on pistils of R. macounii and got a number of seedlings. These were pollen-fertile in spite of the fact that one parent is tetraploid and the other diploid. One of the seedlings was a salmon-pink bicolor that combined the yellow of the one parent with the pink of the other, although both colors were relatively pale. The remainder were pure white.

These days its much easier to understand suppression as a dominant feature. I had thought of it as a gap in a pathway for many years but all we have to do now is to invoke RNAi. HR may suppress the anthocyanin genes coming from AC leaving only yellow at ordinary temps. Previously I had assumed it was a deficiency in matching of the pink pathway between the two parents, and that raising the temp increased the amount of one of them enough to get some pink.

Percy Wright actually enhances my point re AC. A bicolor is distinct from a blend, having distinctive shades front and back. When I cross carefree copper pollen onto other plants generally the color is diluted like that. It doesn’t go all or none.

Rainbow KO pollen on Feu Josef Looymans or Playboy or Golden Slippers sometimes gives very intense red, far more than the sum of, or average of, the two parents. I haven’t recorded data on the ones that don’t show this surprise so I don’t know if it is 1/4 or 1/64, but likely nearer 1/8 in the repeat-blooming decent seedlings.

A small fraction of RKO OP seedlings are yellow, more than 1%, but not a big #. Whether they actually are missing the pink genes, or those are suppressed in the outer segment of the petals I don’t know. Haven’t gotten to the next generation with crossing yet to see if I can make a true-breeding yellow line. Maybe Bob Byrnes has some data coming along.

Another bit of evidence:

The Rose Manual, p. 33 (1844)
Robert Buist

*The Austrian Brier, or, as it is called, Single Yellow Sweet Brier, is very common in many old gardens. The flowers are equally as bright as the Harrisonii, with one side of the petals, in certain stages, inclining to red.

As for the bicolor trait, there seems to be some confusion.

Angew. Chem. Int. Ed. Engl. 30: 654-672 (1991)
The Chemistry of Rose Pigments
Conrad Hans Eugster* and Edith Märki-Fischer

“The petals of white roses reflect a large proportion of the incident light. They are therefore more or less free of compounds that absorb light of wavelength 400-700nm. Nonetheless, the petals are not transparent. This is due to the many air-filled spaces between the cells, the so-called intracellular spaces. When the air is displaced, for example, by dipping a petal into acetone, the luster und reflection are rapidly diminished.”

Without the reflective layer, the uncolored petals would appear limp and insipid. If pigment is present only on the upper surface of the petals, absence of reflective air pockets will allow the light to pass through. Thus, the reverse of the petals will be only a shade lighter than the fronts.

The reflective layer also adds brightness to flowers with color.

It should not have been too difficult to imagine even in the early days of mendelism. Rabbits, for example, have both a recessive white (albino) and a dominant white.

I meant mechanistically at the biochemical level, not for imagining things through thinking by analogy. For plant people to talk of rabbits was once considered hareasy. Just pull one out of a hat. We focused on sweet peas (see my paper on “Origin of the Punnett Square”) not the buggers that eat them. More seriously though, does anyone yet know how dominant white happens?

Punny guy. As to the precise mechanism of dominant non-red in roses, I don’t know. But I’d like to offer a plant analogy.

The so-called Black Mexican sweet corn (actually originating in New England) has white or pale green silks, glumes and anthers. A white corn, to the contrary, typically has pink or red silks, glumes and anthers.

Black Mexican carries a transposon that does little but take up space and “look” foreign. So long as the transposon remains silenced, the kernels are pigmented while the other reproductive bits are not. But when the silencing slips, the pigment distribution flips. In some cases, following inbreeding or outcrossing, there is variegation: some silks white, others red. Likewise, variegation affects the kernels, often white with black dots.

The transposon is relevant in this example only because it is a target for silencing/unsilencing, which allows us to see how something located near the transposon determines whether the red pigment is spread through the silks, glumes and anthers, or concentrated in the kernels.

Coming back to roses (Teas and HTs), we sometimes see clear yellow flowers growing out from red canes and leaves. There is no shortage of red pigment, but it is displayed proudly in the new vegetative growth, not in the petals, but maybe again in the styles and stamens.

Yes, of course. The developmental program switches the pathways on and off to give all sorts of patterns. Red stamens, filaments, stigmas and styles are all independent of the patterns in the petals like central blotch, central yellow eye with sharp changes ( like Golden Slippers to pink or to red outer petal as in Ruby Slippers), or a gradation as in Playboy, Incantation and many others. Some pretty roses depend on a pale petal and bright red central stuff for their attractiveness, like Dainty Bess. But often red stamens turn black or dark brown too soon and then shrivel to a muddy mess in the center of the flower by the 2nd day.

Sweet peas have their various petals variously fused and with different colors. So do snapdragons.

Red cabbage has yellow flowers.

I have little clue what is the “developmental program” coding for any of these. But I don’t think that much if any pigment moves from one cell to another over distances longer than the plasmadesmatal connexions between nearby cells. So there must be some clever coordination of timing gene expression in batches, to get one thing like a sepal green and another like a petal not green.

As far as the dominant inhibition of red/pink, I can add that maybe some of the Pimpinellifoliae may be sources for that trait. Rosa xanthina crossed with a dark magenta rugosa gave all pale yellow seedlings with hardly any trace of pinkness. That same xanthina also completely “bleached” out the pinkness in a cross with palustris.
Somewhat similarly ‘Hazeldean’ lightened the dark pink of rugosa resulting in an apricot colored offspring.

And another possible source of dominant white (non-pink/red) could be Rosa bracteata. I seem to recall, Ralph Moore or Paul Barden mentioning how difficult it was to get saturated color in bracteata hybrids. I’ve also seen this when bracteata was crossed with F1 (rugosa x palustris). Nearly all of these half bracteata seedlings were white or palest pink. Only one was dark enough to really be called pink.

Buck (1960) reported similar results with hybrids or Rosa laxa Retz.

Pollen from the ‘Crimson Glory’-R. laxa seedling was effective in producing viable seed on a wide range of cultivars of the Hybrid Tea, Floribunda, and Grandiflora garden classes. The seedlings segregate into two sharply defined groups of approximately equal numbers. One group bears a pronounced resemblance to R. laxa in growth habit, foliage and prickle characteristics. The flowers, which are borne only in June, are single, two to three inches in diameter, and are in the lighter tones of pink, salmon, and yellow. All the plants in this group are as hardy as the species parent. The plants of the second group resemble the garden rose parent in floral and foliage characteristics. The plants are June-blooming; the everblooming habit of the Hybrid Tea and the remontance of R. laxa being absent. All plants of this group winter-killed during the winter of 1958-59, even though they had been given winter protection. All the seedlings retained the freedom from powdery mildew and the susceptibility to blackspot of the ‘Crimson Glory’-R. laxa parent.


In some of these cases it might be useful to start with “mutants” of the white flowered species. The Scotch roses managed some decent reds and purples. And even R. Fedtschenkoana offers the occasional pinks and light reds.

In some cases non-red flowers are due to an extreme form of striping with little pigment expressed:

The American Naturalist 56: 64-79 (1922)
The Nature of Bud Variations as Indicated by Their Mode of Inheritance (excerpt)
Professor R. A. Emerson
Cornell University
“What appears to be a similar result in Mirabilis has been reported by Correns (1903, 1904). Crosses of a supposedly pure white race with several self-colored pink, yellow, and pale yellow races resulted in every case in plants with strongly red-striped flowers and with numerous self-red flowers or even whole branches of such flowers. Intercrosses of the pink and yellow races gave only self-colored progeny, from which fact it was concluded that the white-flowered race carried a latent factor for striping. It was later discovered that about three per cent. of the flowers of the white race showed minute flecks of red. It was evidently an extremely light, variegated race, rarely if ever throwing somatic self-color mutations when the variegation gene was duplex (homozygous material) but producing such mutations with considerable frequency when that gene was simplex (heterozygous material). Correns concluded that red variegation of Mirabilis flowers is a character that, with self-fertilization or inbreeding, remains almost completely latent, but which, through the entrance of foreign germ plasms, is brought to full expression.”

Similarly, Burbank found a California golden poppy (Eschscholtzia californica) with a thin red stripe on one petal of each flower. From this he eventually bred a new race of crimson poppies.