So I have noticed over the years that dark coloured petals such as purple’s and reds scorch easily in the sun. Is this the case for all roses within these colours or are there exceptions? I love the purple roses however they seem to hate the sun… Has anyone had success breeding roses that scorch less?
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My first thought is that the Laws of Physics would seem to preclude success in this venture. Dark colours absorb more light wavelengths, and there’s no way around that. One could ameliorate certain factors around it (giving extra water, and/or shade-cover during the height of day), but you’d still have scorching outside without it. All my roses are in containers and I find it distressingly difficult to keep up with their water needs during intense heat, which is only getting worse; y’all see that Sunday was the hottest day in RECORDED HISTORY? Faaaack. We have our work cut out for us, for sure.
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I agree that there are physical limits in breeding red or dark purple colored roses without any scorching. Just as a small addition:
In the case of red petal colors, the spectral reflection (spectral albedo) of visible solar radiation is very low in all spectral ranges except red. This means that the petals absorb a high amount of yellow, green and blue radiation, i.e. sunlight from spectral ranges in which the radiative energy is high. It can also be said that dark red rose petals are almost black in all solar spectral ranges and only reflect a little in the red spectral range. The absorbed radiative energy ultimately contributes to the heating of the petals. White petals, on the other hand, reflect all colors of the visible solar spectrum and therefore absorb less energy and heat up less. Water stress maybe a further problem too.
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So effectively the aim should be to breed great shade resistant roses that are red and purple coloured so as to get the best out of those colour ranges
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I wonder what the side effects of trying that route may be? Light colored flowers go with the genes for “shade tolerance” because there has to be something which enables pollinators to find the blooms to generate seeds. Dark colored types often tend to be those which bask in hot sun, frequently suffering mildew and begrudging growth in anything less than full, warm sunny conditions.
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I haven’t personally grown roses with a very deep petal color that don’t also more or less fry to a crisp in the sun, but that may be partly due to the limited options for reasonably disease resistant roses in my climate. There are many posts on the Houzz (formerly GardenWeb) website on this topic. They suggest that there are some darker-petaled roses that handle sun better than others, although various climatic and soil factors come into play. Shade can be helpful in preserving darker blooms, but roses must be much more disease resistant and have very fast repeat to perform satisfactorily with much shade here (and that is a different topic).
Stefan
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For example my indigo is now getting badly scorched, however in the hot weather it also has much less petals! So the bonus is I have managed to collect many anthers. While on the other hand I have seen some red roses that are fine and others that are terrible… Maybe it’s the soil or maybe it’s the rose itself
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Most likely the rose itself combined with the specific situation in which it grows. Sometimes the difference can be as invisible as the amount of available soil moisture. We often don’t think of the existing mitigating circumstances but frequently what works sublimely in one place, fails miserably even just a few feet away as the conditions which permitted it to succeed don’t exist in the other position. Discovering what they might be is the real “fun”.
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Sorry for late reply, I thought I had posted this last month but I guess I never actually hit “reply”
I don’t grow Erinnerung an Brod, but there are HMF comments about it that say it is heat resistant and petals don’t scorch even in a 35-40°c heatwave. Perhaps others here who are more familiar with EaB can confirm/deny.
Also , in the HMF comments on Huddersfield Choral Society, Pacificjade replied to me recommending Stormy Weather (Orafantanov) for a dark-petaled rose that fries significantly less than others. Haven’t tried it yet but it does look very nice.
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That is interesting information about EaB! I can’t remember if I’ve observed its flower response in that kind of weather, but it is once-blooming, and the very hottest weather usually arrives here just after it has finished flowering. Its supposed Rosa setigera background could possibly be credited with a certain amount of heat tolerance. Aside from the timing problem, this would have been a pretty good test year here… I can tell you that the few dark-flowered roses that even attempted to bloom in such heat failed the scorch test badly. We’ve had regular heat waves in that range for months on end (with high nighttime temperatures in keeping with the high humidity). Most roses just looked at the thermometer and said, “No, thanks.”
I had gotten a Stormy Weather once because it was (briefly) reputed to have rose rosette disease resistance, but it was so prone to other diseases that it had a very short life in my garden. Maybe it has some other virtues… now I’ll have to consider whether it might just be worth trying again, although the Pacific Northwest is a very different climate from ours.
Stefan
Erinnerung an Brod could be the answer to purple roses in the sun! Interesting if it holds up. Might get one
A genetic analysis from the book ‘Rosarvet i Nationella genbanken’ is stating,
that the rose ‘Erinnerung an Brod’ has a genetic similarity index of 56.0%, 54.5% and 52.2% to the following three Hybrid Perpetuals, ‘Magna Charta’, ‘Captain Hayward’ and ‘Ulrich Brunner Fils’. The other parent is, as already known, Rosa setigera. Perhaps this little information is of additional interest
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They aren’t my favourite looking roses, however maybe if I get round to checking comments on HMF they might show as also sun sorch resistant