To stratify or not to stratify

Fairly new at germinating op seedlings, and had some success planting seeds that had started germination in the fridge wrapped in moist towels. Would they start on their own if not planted and not in the fridge?

The question is best self-answered depending on how you work, where you live, what your options are, and what the negative may be. My negative is slug damage potential. Otherwise, outdoor sewing without strat is fine. I just have to be vigilant about using non-lethal to dogs/cats slug bait. Otherwise, an entire years worth of work can be eaten in one night flat.

Agreed. I experience better germination when the temps don’t exceed seventy degrees (on average). This is the beginning of fall. Today is to be about 85, with a twenty degree spike in temps within the next week. I stratify to hold them until around Thanksgiving, when I can traditionally expect the temperature range most beneficial for me.

Fortunately, I don’t have the slug problems mentioned above, but I do have to cover them with hardware cloth to keep the bloody squirrels out. Kim

FWIW, coffee grounds apparently have enough caffeine to kill slugs. The additional benefit of applying coffee grounds is that the rose seedlings will get excited and stay up late, working to produce really good flowers. I’ve not seen any information that the flowers will all have the cupped shape.

Kim; All my germination is done in our southern hemisphere winter, I find the greatest germination rate is around 59F and once over 70F the rate starts to drop dramatically. It is now the end of the first month of Spring and all my germination is complete.

All my germination is done outside with no covers, they are only bought in undercover when seedlings have sprouted and there is a frost warning, then back outside in the winter sunshine.


As I am new at this, what has the temp got to do with germination, what happens after 70F.

Warren as you have mentioned, your best rate is between 59F and 70F, can this be explained to the novice please, David.

Dave; Here Deniliquin I found after 20c germination stops, alot of the seed is still ok, but will not sprout.Why this temperature range is optimal, it is something the rose seedling showed me themselves.

As you know most of my seedlings are in the ground by August (our late winter), this gives me a two month buffer to get their roots deep enough to cope with Deniliquin Summer temperatures 38C (100F) to 45C (113F). Any seedling put in after October will suffer greatly.

Peter, you’re a hoot!

I do my seeds in my basement during the winter. It’s never above 70 degrees down there. I’ve tried sowing them outdoors in the spring but had no luck with that at all. Anything that did come up did not survive either the heat of July and August or didn’t make it through it’s first winter.

Jadae, so are you saying stratification is not necessary?

Judith, for many types no major stratification is necessary. My 2010 planted seed received nothing more than being held in approximately fifties to sixties degrees in the work room and they germinated like grass. The 2011 planted seed received weeks to months in the refrigerator and came up at about a 20% rate. Of course, there were many other factors involved, but it is interesting.

To my logic, seeds which contain the genetic programming for extreme cold hardiness should require longer periods of deeper cold to trigger them that winter has passed and germination should be safe. But, what about those which follow the more semi tropical area programming where frosts are seldom encountered? Ever green, less severe cold tolerant types such as Banksiae, China, many Teas, etc., are from areas which don’t experience the depth nor duration of “cold” species such as Rugosa, Virginiana, Arkansana, Nutkana and many European OGR types are subjected to. These, and the modern roses which more closely follow their programming and requirements, often fall from the plant and germinate in place under favorable conditions with no more chill than is offered by climate.

We seldom receive winter temps lower than the high thirties, with those in the forties being much more common. Yet, seed germinate here by themselves frequently. They are from modern hybrids which should, I’d think, contain more of the less cold hardy programming. Sometimes, my germination seems higher when I don’t stratify. Last year, it didn’t and was tremendously slower than my “norm”. In 2010, they came up fast and furious without any refrigeration. The types planted weren’t that different from one year to the next as I hadn’t grown anything new nor received nor collected seed from things other than I normally plant.

Here, I mainly use refrigeration to hold the seed until the more beneficial temperatures are the expected conditions. It affords no benefit to put them under soil when I have to water them nearly daily to mitigate extreme evaporation due to lower humidity and high heat. Waiting until temps remain below the mid seventies prevents the need to constantly water and prevents the newly emerging seedlings from being scalded or cooked by extreme sun and heat. That’s what I feel the answer to the temperature question asked above is. Seeds of many types have been “naturally selected” for those which germinate under weather conditions which promote their success. Those which might have germinated in higher heat have likely been killed off due to lack of rain and/or being cooked or fried by extremes they wouldn’t experience earlier in the year. They do seem to need some period of cooler temps to make them “think” winter has occurred and germination is safer, but not necessarily weeks of near freezing.

Talking with Ralph Moore about this, he offered that his thought was those which require long, hard periods of deeper cold should tend more to be those which would be more severe cold tolerant, but which well might also be spring to early summer flowering. Repeat flowering and extreme cold hardiness are often contradictory characteristics as the repeat flowering would postpone sufficient hardening of the canes to endure extreme cold and/or dry conditions. The same goes for seeds which require longer than one spring to germinate. Many don’t come up the first year, but sprout the second. His thoughts were those would more likely be the ones more suited for extreme cold climates, not something he concerned himself with in his climate and targeted markets.

Banksiae traditionally requires two years to germinate, though I collected seeds from Lutescens and planted them immediately. One of the eight germinated in only four months from planting and is now 18 months old. None of the others ever came up. I kept the pot they were in until last month. The winter it experienced as a seed in a hip was rather mild and it was sheltered by the overhanging limps of a tree, so it received little real “stratification”.

Is stratification “necessary”? For some, probably, but not for all and probably not for only the reasons of permitting germination. Often, to prevent it from happening before it is convenient and possibly best. Kim

Hi Judith,

My answer would be like Kim’s answer – it is dependent on the locale and the person’s preferred methods. It is also dependant on certain species. Where I live, I let the rain do its work for me.

What’s “rain”? LOL! Kim

Something desert rats dont get, lol.

Kim you mention ‘modern’ roses in your post, forgetting locality for the present, do you think they would reguire less or no stratification than ‘OGR,s’.

Would statification times(length & cold) if they are used be relevant to ‘class’ of rose, lets say the 'Pernetians" against ‘China,s’. This question goes to you as well Jadae.

I would think those which more closely follow Teas, Chinas, Noisettes, minis, etc. would require less to no chill compared to those which relate more to the Damask, Gallica, Alba, cold hardy, Northern European types. Definitely not written in stone as I would imagine Nature has programmed some of them to germinate with less stratification in case of climate change or milder patterns of winter weather. “She” has a wonderful ability to keep such things in mind and make allowances for them to handle just about any eventuality.

Gallicas are more cold hardy than Hybrid Chinas which more closely resemble China than “pure” Gallica. I would suspect the more once flowering and cold hardy the rose, the potentially greater the need for colder, longer stratification. Not based upon any hard, scientific research, but more on where the roses occurred, were selected and where they succeed best. “Feelings” for what they potentially require based upon how they perform in different climates.

Perhaps a self of Soliel d’Or might require longer, colder stratification than say a Ville de Paris self seed. The former is closer to the “species” and a hardier OGR, while the latter has less of those influences and more of the evergreen Tea traits. But, that could be totally off base, FWIW. Kim

Thanks Kim

You’re welcome David, as I said, it may have merit or it may be mulch. I dunno, but that’s what is logical to me. Kim

I think there’s good evidence that in a Mediterranean climate, natural stratification happens if seeds are planted in late fall. I reviewed work from Italy (Calvino?) done right next to border of France in 1930s. And I believe Meilland talked of direct planting. Seems to me so does Pierre Ruttan.

I was absolutely amazed this past winter when I planted into peat a bunch of seeds from hips that had been stored cold 3 months. I tried warm stratification and got some germination within a few weeks. The CV was I think Chuckles, or something looking very like it that grows in a large apartment complex near where I live.

It also seems that for some species (multiflora, souliana at least) dry storage for weeks to years is fine but David Z. has shown for some CV that even a short while dry is bad. And I got absolutley nothing from seeds stored dry in the hip 3 months while those kept moist in frig give tolerable germination if put into moist peat. So it is all very complicated.

Thanks for your answers. So I guess the bottom line is, rose genetics for modern roses is complex, and perhaps it is just safer to stratify then not to stratify, especially when the timing suits your planting plans?

Makes it a whole lot easier, Judith. I don’t think you can HURT anything, but it can make timing better, giving you some breathing room. Kim