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Stratification period?

Posted: Wed May 15, 2019 4:19 pm
by macabreroses
Hi! Wanted to ask how long some of you generally stratify your seeds! I’m fairly small scale so I generally use a fridge but wanted to know how many weeks you left them before pulling.

Re: Stratification period?

Posted: Wed May 15, 2019 11:53 pm
by roseseek
I'm in Zone 9b, Central California Coast. I don't stratify any of them, period.

Re: Stratification period?

Posted: Thu May 16, 2019 12:22 am
by philip_la
Those folks in California will make you crazy if you listen to them. Everything is effortless in CA. ;-) (Kim, do you sow your seeds green? Or how do you avoid the dormancy issue?)

I admittedly have not done any experiments to compare approaches, but the technique I used years ago, and which I resumed when I started breeding again, is to leave small planted baggies a good 2 months in the fridge (making sure it's not set cold enough to risk freezing germinating seedlings) then pull 'em out for a couple weeks, prick the germinating roses, then return remainder to fridge for a few weeks in, followed by a few days out, over and over again until, like popping popcorn, it seems to no longer merit the effort. I have had seeds from one cross vary in germinations from 2 months to nearly a year, but that is highly atypical. Usually by the third sortee from the fridge, the bulk of those that will do so appear to have germinated, at which point I typically dump the remaining contents of baggie into a pot.)

I do a very small number compared to most here, however, so pay the advice of others more heed than anything I say.

Re: Stratification period?

Posted: Thu May 16, 2019 1:06 am
by roseseek
We don't "DO" dormancy, Philip! But, I don't mess with Arctic hardy types, either, or those which I DO mess with, also have seeds which don't require an "ice age" to occur to yield germination. I don't touch Rugosas. Not that I don't like them, they HATE it here. When I was stupid enough to touch them, they germinated like winter rye grass. Then, they rusted and black spotted like everything else unsuited for our endless summer.

Re: Stratification period?

Posted: Thu May 16, 2019 10:06 am
by Larry Davis
Philip, I do sort of like you, but with the calcium nitrate added to vermiculite. I check regularly every month for a year while holding the seeds at 4C (40F) in a standard refrigerator from the 1950s. I have also done deliberate cycling like von Abrams and Hand did back in the 1950s. They did 4 cycles of 3 months in, one month out or something like that, for all of their crosses.

As Kim noted, rugosas sprout like weeds and do not benefit much if at all from cycling. I've never seen blackspot on them here. Must be a different fungal strain out west. Caninas definitely benefit from the cycles if they have gone dormant by fully ripening in the hips. They are a stubborn lot and vary from year to year in how they respond. I've got some running on 4 years now with occasional sprouts still popping up.

I've not documented but based on lit review, it seems that in a mediterranean climate the cycling happens naturally if you plant more or less outside. That approach was very successful in southern France and Italy, and California too.

For complex hybrids, its all over the place. Generally what's worth getting is gotten by 1 yr. For an odd cross with a species or near-species, I may continue longer with warm cycles after the 1 yr in cold. Some types like the KO series take 6-10 months. Others may peak at 3 months and never give another sprout no matter what I try.

I do from 200-500 packets a year (some are replicates or variants). Some day I'll publish the rest and maybe be able to draw some conclusions.

Re: Stratification period?

Posted: Thu May 16, 2019 4:14 pm
by jbergeson
I change my method every year but it usually involves 1 month or more of room temperature moist stratification in baggies, followed by a month in the fridge, then I sow the seeds in seedling flats and return them to refrigerator temps for another two or three months.

Re: Stratification period?

Posted: Thu May 16, 2019 6:29 pm
by Plazbo
Sydney australia here, similar to Kim but rugosa's dont seem to have issue here. No stratification required. Just straight into seedling trays at the end of summer. Things germinate during autumn, some flowering before winter. Summer heat will kill seedlings but winter temps don't, freezing temps for a total of 3 hours over the whole of winter and even then its only just freezing.