Got lucky once with a jumbo hardy in the beginning days not so long ago.
Prairie Dawn, germinated one OP or crossed seedling when seed batch taken to the southerners manual suggested temp above zero (~4C).
Still have it in garden as my historical first germination milestone. And still waiting for it to bloom.
Rest tossed based setting ~July as my tolerated practical limit to watch moss grow above zero C.
Decided to spend money and pay for power to stratify just below 0C.
Better rates as an aggregate, but lots of “zeros” for some hardy varieties, and others very high rates, almost poppy rates (eg R xanthina, R beggeriana, R. spino hybrids o/s and c/w rodent catalyst, and R altaica).
A species R. spino from Pickering didn’t survive 4 winters when l thought it should. Probably a variable point weird result - considering crosses and R altaica does.
One thing thats been constant for me is germination rate variability high to 0 between crop seasons for some same hardy variety and same plant.
Average for all varieties combined very low. But faster for me to get a lot more if they want to germinate without going to hundreds of seeds and 1/2 seedling per 100 proof - done it been there got the moss to prove it.
The reaper is creeping close and need my hardy red climber success - once bloomer? Dont care..
PS
Since life of thread reaching newness limit of interest and originator got his ideas to try and a plan. I will expand at risk of hijacking critiques.
Doing so, because l am pretty sure lack of successful germination at levels where people lay their first expectations can be off putting to carrying on. Been there.
The above/below is an amateur (by moi) draft empirical informal dissertation (non peer reviewed) for temperature test influence on my germination by me (lots of temperature papers out there but not found any to-date for below 0C for cold zone or “Arctic” rose).
Is it required - nope, stay where it mimics your “dormant season temps”, nope stay where you are, its safer from criticism.
Did get peer reviewed once in another field … place 2nd in country … been downhill ever since.
Tested crossed and non crossed. Concluded germinations were great for those that wanted to. Best the species, but also hybridized cold zone roses and crosses (tender x cold).
But this only happened for me when dropped slightly below 0C.
Prior to going my route, tested the status quo method and it was a flop over two seasons, based on “1” germination.
The results of my first reconnaissance crossing survey germinations back in 2022 using a lower limit for stratification, were eye opening for me.
In 2022 l went crossing for real.
Have about ~ 150 varieties, down from 500 about 20 years ago when went trying hardy and protected out of zoners from sweaty places.
… now hybridizing cowboy approach test results. My record indicates l did 78 crosses (no strict science crossing criteria eg ploidy ) in 2022.
Though by fluke a lot were tetras. Harvested 1568 seeds and got 15 germinations. Or ~1%.
And germinations done using just below zero C stratification. For a few months followed by about 2-3 weeks at 18C. Seven cold - ambient cycles in all. But cold cut to 2-3 weeks.
Some were Merveille - about 9 variety pollen donator crossings. Chose her because year before got op germinations from her seeds.
A second test last season … same “result character” and happy I am still going. A real challenge setup this year with lykkefund crossings.
… txs to Merveille only. And loving it, even after few vocal blind rages at germination, because had some important to me manageable successes … and l am still way down the hybridizing learning curve.
I just went engineer prudent risk taking based on observations - happy as Larry when l rationalized not going to happen getting common poppy germination rates for all rose seeds from a crossing season as an average … more like meconopsis rates during a blue moon phase. Still waiting to get my first using directions on seed pack.
Forgot to mention key mental trigger soil and air below zero - snow theoretically just below 0 C … if the reason or not, don’t care basis worked for me. Experiment, nothing written in stone.
after trying live plants x 2. They were expensive, but not tissue culture expensive as for itoh peonies back 5–10 years ago.
… know how one pack of seeds is going to be “conditioned as an experiment”…