I believe that the R.rubiginosa used by Kordes was ‘Magnifica’ - a tetraploid seedling of ‘Lucy Ashton’



Rosa rubiginosa should give 4X ovules and 1X pollen. When selfing or crossing with another rubiginosa this would give back the normal pentaploid (5X) ploidy.

Crossing with diploids… with rubiginosa as the seed parent should give pentaploids; with rubiginosa as pollen parent should give diploids.

Crossing with tetraploids… with rubiginosa as the seed parent should give hexaploids; with rubiginosa as pollen parent should give triploids.

These are the theoretical expected results based on what little is known of the rather unusual meiosis of the Caninae species, but you never know for sure what unexpected results a cross might give.

Best of luck to you, whatever you try with it.



Thankyou very much for this excellent answer… hexaploids sound interesting… I wonder if there is any advantage in having so many extra chromosomes???

I like the sound of the diploid rubiginosa hybrid actually.

Hi Simon,

Hexaploids might be great breeders to use as pollen parents with modern tetraploids.

The Albas are supposed to generally be hexaploids being derived from Rosa canina crossed with old garden tetraploids. They’re supposed to make 4X ovules and 2X pollen, so could be used as pollen parents on tetraploids to make more tetraploids. Rolf Seivers did some intersting work with Albas combining them with kordesii derivatives.

As for a diploid rubiginosa, that could be very interesting, but just for your information [hopefully not to discourage you in any way]… I did a cross many years ago of Rosa rugosa X rubiginosa. At the time, I hadn’t read anything about the odd meiosis of Caninae and was fully expecting a monster of a hybrid. To the contrary, the offspring were all runty, yellowish-green plants. when they finally bloomed, they were equally pathetic at that. The petals were shriveled - looking like crumpled crepe paper. So I’d recommend that you try as many different diploid parents as you can, to try to find the best matches. And steer away from using rugosa as a seed parent with rubiginosa if you might have been considering that one.

Best of luck to you. I look forward to hearing about your progress.


Thanks again Tom,

I was actually thinking of some of the diploid Teas like Mons. Tillier and Safrano…

Sowed a few OP hips of Alchymist, and have had a good many seedlings germinate. Has the ploidy of Alchymist been sorted at this point? How likey is juvenile-bloom?

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At best it could be triploid. Probably it is diploid. Anything higher than triploid would be unlikely if the parentage on HMF is correct. This is my personal opinion.
Chances of juvenile bloom seem unlikely. If she has some recessive repeat bloom, with a good repeater you could have 1/4 repeating seedlings. But that would be a long shot.
I’d love to hear if you managed to get repeating bloom. Anything is possible with roses.

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