Hi Tom.
I just stumbled upon this conversation in the archives, where David mentions a Rugosa X Polyantha cross (see link below). I hope this is what you are referring to. It is indeed a very interesting idea!
BTW, I think your hybrid multiflora / hybrid rugosa is magnificent.
Link: www.rosehybridizers.org/forum/message.php?topid=23392#23394
Yes! Thanks George!
That post was exactly what I was trying to remember.
And thanks for the kind words too!
Simon, I’m not certain that it makes the difference, but I never got any seeds using the rugosa as the seed parent. But, I got the cross to work in the opposite direction at least this one time. And don’t overlook what David Zlesak was saying in that post George found - that it would be best to try as many different rugosas and as many different polyanthas/multifloras as you can find.