A respected person on this forum said that, at least where I live, San Francisco Bay Area, stratification is unnecessary. So, I did a trial. Last October, I planted about 100 seeds from a known productive cross (Oso Easy Italian Ice x Rainbow’s End.). I put another 100 of the cross in the fridge for stratification. Now–March 23–I have ZERO germination from those I planted without stratification, while I got my usual 20+% germination from those I did stratify.
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I believe it may depend on the class of rose you are working with as well as micro-climate variations, but where I am, I always stratify. (Still getting abysmal… err… none… germination this year, and wonder if it was poor handling or the medium. Very frustrating…)
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Among other factors, quite probably. I am who suggested cold stratification isn’t always required as it hasn’t been for me for years. What roses you’re working with as well as year to year variations can easily cause differences in germination rates. Experiment and figure out what works best for you, where you are, with what you wish to work and the level of effort you wish to provide. I’ve not cold stratified for many years and what I want to play with germinates for me in the rates acceptable to me. YMMV.
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I am hopelessly biased, quick to quit a method in the early days and stick with what first worked at better than one time for one seed. Changed after 2 years of failure.
Now I stratify but at slightly < 0 C for 90 days +/- . Only once have l seen germination at < 0 C in tray. This approach trys to imitate winter seed temperature surroundings.
Then to ambient and after 14-21days duds back in for 2-3 weeks re- chill. Done a max of 7 once before l tossed them - usually healthy straggler’s show up after 3 cycles.
My rates improved, but highly variable from majority of trays = 0, to 1-3% per tray, to 40 % select trays and species.
This year 0% after 1 recycle.
March 24
Put into frig at < 0C today for 2nd recycle after 3 weeks at ambient with no germinations.. Multiflora x hardy, Spinos and Polstjarnan crosses
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Thanks for being the pioneer, and taking the arrows in the name of science! Do you intend now to do a late stratification on the ones that didn’t germinate?
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I hadn’t thought of it, but now that you mention it…. Thanks. Will do–75 to the fridge, 25 left out as a control group.
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Ihadn’t thought of it, but now that you mention it….Thanks: 75 to the fridge, 25 left outside as a control group.
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I historically would return seeds to cooler in a couple weeks, and out a few days after my initial stratification, repeating until, like popping popcorn, the germinations slowed to a near halt.
I think syratifying after a warm moist period is regardless the methodology of many.
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I’ve discovered that rose stratification works best for me in only a slightly damp mix, kept at 37 degrees F for about 90 days. I take the seeds out of the refrigerator about once every 7 days to room temperature for about 2 hours, and then return them to the refrig. This simulates the normal winter temperature fluctuations. After 90 days of this, I remove to room temps (70-80) and get very good germination rates. Using this method also produces a good number of seeds germinating in the refrigerator.
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