The Magic Stratification Question

Ok so I’m beginning to harvest the last of my nearly hundred or so different crosses from this year’s breeding season. As you can all probably identify with, after all that time and investment of planinng out crosses, executing them, waiting, waiting and more waiting, harvesting hips, cleaning and preparing seeds for stratification, I really don’t want to screw up on the last step. Obviously I’ve done this before but my successes so far in germination may have been mainly due to luck. So the magic question, I’ve heard just about everything under the sun as far as time goes, such as 2 months, 3 months, 4 months, and even a few I’ve read about online who had germination at 1 month, but in a nutshell, which one is it? I’ve heard mostly the two months but so far I’ve never gotten germination personally until four months! I’m not asking about technique or methods per se, just time, but after the time is up is it better to keep them in the fridge until they sprout or plant them? Also, earlier this month I had a batch of assorted Knock Out seeds, after 3 months, begin to sprout but I fear I may have broken the 80degF barrier as germination was suddenly and abruptly halted after moving them to my sunroom. Do I have to wait a whole nother 3 months in the fridge to re-activate germination? Thanks guys!

You ask really hard questions. There is no one right answer. Best evidence is that keeping in constant cold extends germ about 2 mo compared to intervals tested every month or 2 with same species (Semeniuk and co-workers at USDA, 1960s). VonAbrams and Hand did repeated cycles of cold, warm, cold, warm, cold, warm to maximize germ. For some CVs and spp, warm before cold is beneficial. For others, no difference. For me the KO types take many months at best. Dry storage hurts some CV (Zlesak) while long dry improves others (several refs).

I am not sure I’m answering your question, most of my seeds are from near species crossed with flourabunda,teas and some shrubs. I follow the 3 months damp warm in peat,followed by 3 months in the fridge.
I had taken a break from hybridizing and stored 2008 seeds in the freezer.Last fall I took some out and put them through the treatment. After 5 years in storage, I’m pleasantly surprise at the percentage germination I got.

Has anyone ever done this? How Long are rose seeds viable for?

With plants in general there is the idea that stratification duration requirements for seeds tend to parallel the dormancy period of the parents that is also released by cold. I tend to stratify longer than I need to because we have long winters here and my plant stand can get crowded by spring. I tend to use warm before cold to help delay germination too and then when they start germinating in the fridge pull them out. What hasn’t started germinating in the fridge by mid January I just pull out to try to jumpstart.

So, what if you don’t get “cold”? Most years, this coming winter in particular, the roses don’t actually stop flowering. This winter is expected to be warmer and wetter than “normal”, especially compared to the past several. My “stratification” period is generally from the last harvest until about the week of Thanksgiving, when it is traditionally “cold” enough for them to germinate and the rains used to begin. I counted on the colder temps and rain to stimulate germination and keep them watered for me.

Question for ChuckP- I’m curious about the freezing. Were these cold-hardy crosses? Did you freeze them in their damp mix, IE moist soil or paper towels? What temperature is your freezer?

The reason I ask is I have a good number of seeds this fall, and it turns out I may be overseas next spring. Putting them into hibernation for a year might be a solution.


I germinated rose embryos that had been stored by the USDA for 25 years and now have two fine R. omeiensis specimens taller than me from them. I do not how they were stored but iirc it was by deep freeze.

You don’t have to freeze your seeds to keep them for only a couple of years, though. Just dry them well and keep them in the fridge after they are dry.

Here’s a blurb that spells out the steps and specs for drying and storing seeds, for which you can consider rose seeds to be ‘orthodox’.

hi Donald, My comments go beyond casual intererest. I have 40,000 seeds in my home deep freezer. They in no way I’m able to germinate that many seed in the near future. I was hoping that someone had experience this before,that would tell me how much time I have. Next spring I plan to start hybridizing again,naturally I’m anxious to see what the new crop of seeds generate.

To answer your question, the seeds are stored dry without a grow medium in 1l. ziplock bags, as a side note. A month into the warm treatment on top of the kitchen cupboards, I got a burst of germination.
most of my crosses are explorer x tender roses.
The temperature of the freezer,just what you would have so your Thanks Giving turkey does not spoil.

I have a somewhat related question. I have more seed than what is normal for me this year. I do not have the room to take care of too many early germinating ones. How can I time my stratification that so most of my germination is occurring as the weather is getting warm outside?

Generally speaking, if you keep seeds in the hips they don’t advance much toward germination. So if you start stratification later you’ll get your desired effect. Also simply keeping seeds in the cold and never moving them to warm situation give a 2 month delay compared to cool then warm approaches. This may not be true for some of the teas and chinas or other tropical types which don’t always recognize what winter is about. I have used a lot of seeds kept in hips until the new year and they do OK. I think Paul Barden has observed the same.

Thanks. I will try keeping them in the hip a bit longer. Last year I had many magnolia seeds begin germination in stratification long before Christmas. I was not equipped to deal with that and lost most of them. I generally have a few roses germinate while in the fridge, but don’t want a replay of last year.

Thanks everyone for the informative answers! Turns out i just had my first successful embryo extraction. The thought of bypassing stratification is alluring but has proven to be tedious. I would still stick with the old fashioned way with most seeds, but if you’ve got some you’re willing to expirament on then it’s worth a try. Like I said I’ve never gotten a purebred knockout family seed to germinate, but that all changed in the past week! Hypothesis for other breeders: knock out or any other BS/Mildew resistant DNA in an embryo seems to better equip it for surgical removal from the seed.

To bypass stratification there is an easy and proven way some like Robert Neil do take that is immediately sowing the freshly extracted seeds.

Immediately sewing the seeds in a suitable climate can work perfectly. I’ve done it with good success here when hips were harvested late. I’m only refrigerating them currently to hold them from harvest to planting, about two months.

Do you refrigerate them dry or damp?

Initially, I refrigerated them damp, on damp toweling with Captan. What a snotty mess, plus, it exposed me to Captan. My method has morphed into storing them shelled and dry, with no fungicides. It works the majority of the time with no goopy junk growing on the seeds. What I had noticed was, those which fostered gray, goopy stuff growing on them were low germinators anyway. I can’t compare germination rates between initial fungicide treated batchs of 30 years ago and those dry, untreated today. What I can tell you is, I continue germinating far more seedlings than I can handle, using a very inexpensive, very easy, non toxic method. I notice greater variations in germination due to what I consider winter weather conditions than I can detect from storage methods. The years I sewed the seed straight from the hips with no refrigeration (later harvest) was a wet, cold winter and they came up by the droves. The next year, I refrigerated them due to earlier harvest and later “cold” weather. “Winter” was milder than the previous spring with significantly less rainfall and the rate was substantially lower. How that might translate to anywhere else, I have no idea. Perhaps if you’re using more reluctant seed setters and/or reluctant germinators, stratification methods may be more important. I usually don’t use those known for reluctant seed set or germination as I feel that is too likely to breed that trait into the line I wish to create.

I may have ‘accidentally’ happened on to something that seems to have cleaned up the fungusy, goopy, gunky stuff growing on the seeds when they are refrigerated damp (not sopping, just damp) and that is by rinsing them well with extremely hot water (from the tap) by spraying with the spray attachment. I did this accidentally and noticed that the residual hairs, fruit goop, etc., were both removed much better, and if not completely cleaned, made for easier removal. I always seem to have a few here and there that get by with some fruit attached, and this really shows up big time when they are being stratified. Since most of mine are picked by the end of Aug, Sept., and I do not want to get much in the way of seedlings until after the holidays, they are subjected to a bit longer in the fridge. For those who worry about very hot water (this is not boiling) most plant parts, including the flowers, withstand dips into hot water with no ill effects. Floral arrangers use this to revive floppy stems all the time. I did believe at one time that boiling water would kill a plant instantly until I tried to kill a young Eucalyptus sapling with 5 gals of boiling water to the root region. It responded by growing faster than it ever had before, possibly just because it got some water at all.

Interesting idea, Jackie, thanks. I think I remember reading a fast, hot bath has also been used on fragile berries to improve their longevity in the fridge.

Question If I had some seeds now and placed them in some hot water for a period of time ? then planted them straight up would that work with this idea

I don’t think you want to soak them in hot water, David, more like rinse them thoroughly with the hot water to sort of sterilize their exteriors. Soaking them might actually damage or “cook” the embryos. Since you’re not storing them, but planting them immediately, I can’t see any benefit of the hot water treatment. I’ve not observed rose seeds molding in the seed tables. I have observed them molding on damp toweling in closed plastic bags, or even without the toweling, when stored damp in sealed bags.