How long to cold stratify?

All my seeds have been in cold stratification for 3 months.

Some seem to be finishing up germinating. Some are just starting and others still show no signs of life.

What is the prevaling wisdom here? Do I keep the seeds that haven’t germinated yet in the fridge longer? Because they need more time. Or do I take them out and hope that the warmer temperture will spur germination?



I’v shut down the power of my fridge and it’s 6 to 10 Degrees Celsius. My brother told me 10 is a realy good tempature for germination…it works. Last night 1 Treasure Trove x Golf, 1 unknows OP and 2 Golden Celeb x Pink Cloud seeds sprouted. I had them for 3 months in the fridge. I’ve 28 in total now.

Thanks Timo,

I had to convert the temps to 42 to 48 degrees Fahrenheit because I’m one of those silly Americans that can’t be like the rest of the world. That is colder than I would have thought. I was thinking more like 60 Deg. F (18 Deg. C). But if that is what works then I’ll try it. I have a back room in the basement that stays about 50 Deg F (11 Deg. C) if I keep the door closed.


"Do I keep the seeds that haven’t germinated yet in the fridge longer?’

Paul, you can but it’s also good to take them out for a few days. This sometimes triggers germination. If the seeds don’t germinate, then put them back in the fridge for a few more weeks until they do. If you have to, repeat the above process.

I find the best temperature to germinate rose seed is just above freezing to 4 C (39 F). I rarely work with Floribunda or Hybrid Tea seed, which likely can germinate under higher tempera- tures.

Note: Spinosissima seeds usually take two years or more to germinate.

That’s a great question Paul,

I was surprised to learn the influence on final percentage and rate over time there was between 5, 10 and 12 weeks cold stratification on Carefree Beauty and Rosa eglanteria seeds. It’s a sideline in an article I wrote in the current RHA newsletter on the influence of Ethephon and a low oxygen environment on rose seed germination. The longer the cold stratification, the sooner and more uniform germination occurred, especially for the 10 and 12 week durations. There’s nice tables as I followed germination for 12 more weeks after coming out of the fridge and there are replications and standard error bars on the graph.

I really enjoyed the opportunity to be at a germination seminar with Drs. Carl and Jerry Baskin a few years back and that really helped to change my perspective of looking at germination more quantitatively and considering more factors associated with it. I think there is a lot more we can be trying with warm stratification before cold, especially with some of the more difficult to germinate rose species and hybrids. Also, as Paul Olsen mentioned and I know George Mander attests to, alternations in temperature too.

Timo, I’ve found that polyantha roses and some others seem to germinate better with cold strat at warmer temps like you are using and rot just above freezing.

I think there is a lot more we can learn about rose germination and much of what works best will be very germplasm specific. Roses are native so so many different climates and our modern rose cultivars have a lot in their background. It seems like many of our more developed germplasm (Bucks, minis…) tend to have pretty good germination and are easier than species and others. Perhaps there has just been indirect selection for those that germinate better with less dormancy over time. What breeders are able to raise and obtain over time have genetic makeups that tend to be more conducive to our germination environments with less of a need to have higher rates of dormancy like would more likely be of benefit in harsh temperate climates.



Thanks for the information guys.


That was a very nice article. I didn

I’ve collected a huge amouth of OP seeds from a rose (UNK30) and I took them out of the fridge (4 degrees celsius) and put them in my livingroom. The tempature in the room was 16 till 21 celcius. After a little periode they came up all at the same time.

Some weeks later OP seeds from UNK103, UNK11, UNK28, UNK100 and UNK106 germinated. Each all on the same time.

Before I knew it I was +300 seedlings richer.

All these OP seeds are from Canina and Multiflora species and descendant from them. These are native in Europe and I think copying the most productive environment (winter, spring, summer and fall) is very easy to do.

But my own crosses with New Dawn, Golden celebration, Pink Cloud are coming sporadic or not with the same threatment. As you all know, these have china genes. Could it be that these hybrides have an other habit and need another way to stratification and germination?

Also Rosa Rugosa and it’s descendant Frau Dagmar Hastrup are different. I collected +1000 seeds from really nice fully red hips. At tempature of 16-20 they come up but not at once, also sporadic. Now I have them at the 6-10 celsius area and since no one came up so far.

My goal allready was single flowered roses and these findings on how easy native seeds germinate, gives me a more stronger feeling to use them. Maybe I can increase germination and have a better chance on success.

Some seed will germinate straight way without any stratification.


That’s great that you have so many seedlings. I don’t know if european species are easier to germinate. I was able to germinate R.glauca seeds easily four years ago, but last year I didn’t have any germinate. As Paul says Spinosissima seeds usually take two years or more to germinate also. I think it depends on a lot of factors.

Now that you mention your seeds germinating so well at room temp. Here is what happened several years ago when I germinated some R.rugosa seeds. I had forgotten about this. I stratified the rugosa seeds at 4 C (40 F) for three months and got sporatic germination from them. I took them out and kept them at room temp. Within a week they started germinating like crazy. I had more seedlings than I knew what to do with.

But this was after some seeds germinated already. I didn’t know if I should take seeds out before they had started germinating.


Funny thing.

3 weeks ago I put Rugosa OP and Dagmar Hastrup OP seeds in the 6-10 C. zone but nothing happened.

So friday I took them back inside (18 C zone) to see what happens. Today I looked in the box and 9 seeds where cracked.

After stratification rugosa seeds love to germinate at high tempature. Paul, I think your foundings and my foundings are 100% simular. Can we scientific conclude (if it allready was concluded) that rugosa seeds must be stored inside after 3 months at high temperture to get very fast success? I’m a rookie, maybe this was allready known by millions of rosebreeders :smiley:.

Hi Timo,

I remember reading on the forum that some breeders didn


I’ve got to be more of a rookie than you and the other millions!

(1) What medium are y’all using for stratification? Do you use a separate refrigerator just for roses or do you just use the family refrigerator?

(2)I read in another article or forum (can’t remeber which) that some species seeds make take a year to germinate. If so, how do you store them that long?

Many thanks – Bob (Zone 9 New Orleans)

When I used a sunroom, I rotated in and out of refrigerators in a more or less systematic way which I felt compensated for variable germination requirements. See:

Now, after keeping the hips in my attached (but unheated garage) until I clean them in March or April, I keep the seeds in refrigerators all of the time (normal temperatures in the middle upper 50s-lower 60s (Fahrenheit); but every once in a while (normally when germination slows down) I turn the refrigerators off but still leave the red LEDs on. This takes the internal temperature into the 70s. After a day or two at this higher temperature, I turn the refrigerators back on (normal temperatures in the middle upper 50s-lower 60s (Fahrenheit)).


Henry: WOW! Your link shows a great generosity of time. Thanks. Bob