Hi David
Good to know cold and ambient (indoor) cycling appears to have benefits for those with germination challenges for hardy crossed roses/ species ( eg R. xanthina x Tove J. germinated).
l was very surprised in 2023 there were no germinations after 1st ambient test at 4 weeks after slightly below 0C conditioning of seeds for ~4 months (po-d more like it). Thought l had it beat with conditioning seeds at just below 0C when germinated two OPs varieties to the tune of 7 and 9 count.
And was also afflicted with borderline rose rage because the 2023 conditioned cross seeds were from a survey of 65-70 tender x hardy and hardy x hardy crosses (pretty much random crossing selection of partners).
Aka done that way (random crossing survey) as concluded had too many varieties to study breeding odds when only managed to germinate two OP in years before of the purple gallica and R xanthina. No point to it.
Tackling getting germination basics was the first step for me, (aka) no point in worrying about crossing. Thought statistical odds were in my favour for compatibility to go random to test germination method on a large scale. Didn’t work on two counts, no germinations after 1st ambient and no idea if compatibility issue or germination technique.
But giving up on 1,500 stratified 2022 cross seeds when they failed to germinate after using the same 0C conditioning was “Not” an option for the 2023 venture.
No idea where l got the idea to cycle. l tried it in February 2023 with cycle 2, with the first ambient cycle 1500 duds (0% germination). The gallica crosses exploded out of the beds with cycle 2.
But not at below zero 0C, but using for cycle 2 the 2-4C UK tests lower range stratification results indicator from RHS Wisely in the previous century (1920’s - think Lee or some other posted paper link l read).
The rest is history as cycling worked for kick starting some of my crosses.
But numbers reality check time for 2022 random crossing survey results, … in-terms of successful germinations of 65-70 crosses, l got <4%.
As l seem to have learned a germination tool bag trick, maybe in future using semi-empirical science and judgement together can now be used to pick partners with some degree of confidence it might up the score.
In terms of applying a pre-testing science approach in 2023, it was only used in selecting and deciding on purple seed parent and cross pollen partners (success only when using tetras) result was 66%. The seed yellow and purple parents were selected from the successful OP germination testing in 2021 (a gallica and R xanthina).
Only triploid and diploid pollen parents did not work on the purple seed parent (eg RDxS).
