I’m a home gardener in Central Texas and I’d like to try breeding roses. I understand that ploidy is important. Is it generally difficult to cross diploids with tetraploids?
Any idea what the ploidy of Shadow Dancer could be? It’s the offspring of Dortmund and a seedling of Dortmund, if that helps.
I’d also like to know the ploidy of Cinco de Mayo and Valentine (floribunda, 1950).
Those three and a Mutabilis are my only roses right now, but I may be able to get some more. At least Shadow Dancer and Mutabilis set a lot of hips, so that’s good for me….
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Shadow Dancer is most likely a tetraploid, as is Cinco de Mayo. Valentine is a cross of a diploid and a tetraploid and most likely a triploid. Mutabilis is a diploid. If you haven’t already found helpmefind.com, the description page of each variety there can frequently tell you the ploidy of the variety.
Mark
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Thanks, mwesson. I had found helpmefind.com, but it doesn’t list the ploidy of any of my roses but Mutabilis. It’s a shame Valentine is triploid, since I guess those are hard to breed from and Valentine is very floriferous, which is a nice quality to breed for.
Still, I have the other three, which should be plenty to start with.
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I’m not familiar with Valentine, but there are a great many fertile triploids. That’s a topic that’s discussed frequently here. I wouldn’t assume anything without trying it for yourself.
Mark
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Being upfront, I am a beginner too. I did a lot of research on this subject. What I’ve learned is to not worry about ploidy too much and just let roses figure it out.
If you’re interested in the biology behind ploidy, I highly recommend reading Ueckert’s thesis here.
The basic gist for 2n x 4n from the study is that it has 81% hip setting success with 24% germination success.
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Agreed. I had an old nurseryman tell me once, when was pestering him about this subject, that “roses can’t read.” My experience has panned out that nugget of truth a few times over the years. I say try everything, both directions if possible. Take note of what you observe; and, above all, have fun my friend.
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Thanks for the tips, all. I’m hoping to eventually develop some good large climbers. People don’t seem to be breeding many of those, but I’d like to grow roses up my house. Seems like most of the really big climbers are pink or white and once-blooming. I’d like to try for more colors and more rebloom.
Of course, I can’t really work on that yet, because I don’t have any large climbers, but it should be fun experimenting/practicing with the ones I have. They’re some good roses, and hopefully have a lot of good genes.
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Thank you for that paper. I am shocked at the overall high success with triploids. I had always thought those to be the most problematic.
And I too no longer sweat ploidys. It’s easier to just experiment. I think of how many failures Pernet-Ducher had with Foetida, and that gives me some hope and solace that I’m not just wasting my time 
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The study that Ueckert did was rather limited. He used only ‘Homerun’ as the triploid pollen. He also only used ‘Jacquie Williams’ as triploid seed parent. I want to clarify that this study is not exhaustive nor conclusive.
I thought that the most interesting insight about triploid roses is that they have highly varied pollen sizes. Ueckert wrote that ‘Homerun’ produced majority of pollen as 1n and 2n.
I don’t have any evidence of this claim, however it seems like triploid breeding is dependent on the gamete health of the specific rose varieties. I am also curious about how ploidy influence the egg cells in roses specifically, since Ueckert covered the ploidy’s influence over pollen.
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Don’t assume anything when it comes to ploidy. Some of the most fertile cultivars I have worked with are triploids, and some of the most INFERTILE are tetraploids. Triploids can be very useful parents.
Golden Angel is a triploid, and yet it readily produces viable seed (and pollen). Out of Yesteryear is a cross of two tetraploid parents and yet it is a triploid with extremely fertile pollen. I crossed Sheri Anne (tetraploid) with Out of Yesteryear (triploid) and the resulting seedlings were a mix of tetraploids and triploids. Ploidy in roses tends to be very fluid and you shouldn’t assume that you’re going to get any specific result when mixing ploidies. Just try some crosses and see what you get. Take notes.
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