Beginner Stratification Questions

I am seeking some advice for my very first harvests. I am trying a two month room temperature stratification, which I will follow with in the fridge. I am keeping them moist in ziplock bags without any other media or fungicides. Is this common practice these days? Images attached. Do they look too dry/wet?

It got cold earlier on and I ended up cutting off lengths of stem with the hips, then brought them indoors in a bucket of water to ripen. The stems are still alive and I am waiting for more hips to ripen. I hope this works.

Any tips would be greatly appreciated, I would love to know what methods everyone is using these days.

Hi Roselynn,

I follow the same principle, 2 months warm on top of the kitchen cupboards. From your photo, it looks like you are
using lunch baggies. If I could suggest, you swap them out for thicker one litre size bads. The walls of those lunch
bags are too thin and your seeds can dry out over time.
I use #1 Pro-Mix starter mix as a medium for stratification of my rose seeds.
I think it’s way too early to start the stratification process. Some of your seeds can start germinating by the end of
February next year. Carrying these seedling so early in the year in your home can be a problem.

Hi Roselynn,
Congratulations on some nice looking healthy seeds from your first harvest! They are looking good so far, but as Chuckp said, they can dry in those empty bags. I do my stratification, both warm and cold, in the ziploc snack bags using a moist perlite to keep them from drying out. I do check them from time to time to see that they do not. I have picked a few hips, but will get most in mid-November here in zone 8. They will be in warm stratification until early December when they go into the fridge for a minimum of 40 days before sowing in late Jan/early Feb.
Hope you have some good germination.
John Moe


As Chuck says, they will dry in the little sandwich baggies- but rather than swapping them out, you can place the sandwich baggies inside a larger freezer zip-lock and keep it sealed. At least that I’m trying this year.

How moist are they in those little baggies? I don’t think they should be sitting in any water at all- if you’re going to have water in the baggies, add perlite or paper towel. Last year I over-moistened them in their bags- they sat in water in the baggies for a couple of months- and coincidentally or not I had poor germination.

Kim Rupert might weigh in here- he places the fresh, moist seeds in baggies without other medium and without water, I think. That’s how I’m doing it at the moment. Then I will plant them in potting soil, in trays, and place them outdoors in January which should give them a few months just above freezing (I’m in the Gulf Islands.)

You seeds look nice and clean.


Hi Roselynn - I’m south of you, in Spokane, but considerably warmer at Zone 5 and work mostly with species and near-species roses. Normally, I harvest and clean hips in early October, put the seeds in barely-moist paper towels and zip-lock bags in the pantry for a month. In early November, I change the paper towels (there’s often a little mold from bits of pulp I missed but it rubs off of healthy seeds - if the seed itself is moldy, I toss it) and put the bags in the fridge for three months. In early February, I sow the seeds in a light potting soil in flats and put them outside. I don’t worry about frost but if the temperature drops into the mid-20’s more than briefly, I move the flats into an unheated garage for the duration. Most of my roses self-sow, if left to their own devices, so it’s a process for tracking the seeds more than providing unmet needs.

I’ve yet to find any better way than what I described a few years ago with moist vermiculite having 10 mM calcium nitrate present. Perlite or peatmoss would work too, but the vermiculite is easier to weigh and measure and hold a known level of moisture. Perlite dust is very irritating to my lungs and dry peat to my nose.

I’ve not found the warm stratification useful. It usually leads to more mold growth and lower germination. Examples of lots of alternatives are given in the newsletters over the past 5 years. If you are working with stubborn species, sometimes cold, warm, cold is beneficial as I’m finding with R pomifera and R caninae. That is like the old reports that 2 winters are needed. It seems as if that is true once the seeds have reached a true dormancy. If you can catch them early, they seem to not need the 2nd cycle. It is also the case that one can get very good results at ambient temperatures, if those cycle down to below refrigerator temps part of the time, as in a weakly heated greenhouse, or in a mediterranean climate.

My best results are 50-80%, including R canina. A lot of crosses are well below 30 %, especially some refractory types like Sunny Knock Out. Still trying to beat that one.


So 10 mM calcium nitrate is how much powder per gallon (or other unit)? I’d have to start back at the Wikipedia definition of ‘mole’ to figure that out.

Do you eventually sow all of the seeds, or are they germinating right in the baggie and being plucked out and planted?

I’m looking for a way to get better germination and an easy way to do things because I have soooo many seeds this year.

How much vermiculite do you need to put in the bag? If you have three tiny seeds of one cross, can you just put in a few grains? Wouldn’t it be difficult to find the seeds if you put in more?

I usually sow my seeds in early winter into open seed flats and store the whole thing in a cold area for several months. It’s fun not to have to transplant in the spring. Maybe I could store in the baggies with vermiculite and calcium nitrate for a couple of months (or less) and then sow them and perhaps continue cold strat in the trays.

Perhaps I could just water my seed trays with a (stronger?) calcium nitrate solution. I think I might use our greenhouse mix of bog peat and rice hulls with a wetting agent and trace nutrients as a base, and cover with a commercial germination mix. So they’d get some biological action perhaps from the peat.

Warm moist stratification is asking for trouble. It gives disease a head start and starves the seeds for oxygen.

Drying seeds preserves their vitality better than chilling alone if long storage times are desired. I dry mine first and then store them in the fridge because I never know which ones I’m going to germinate any given season. This is not the same thing as stratification. For stratification the seeds need to be fully imbibed. I think adding calcium nitrate to the imbibing soak is good advice too.

Rather than be redundant again some other comments on stratification are here:

OK, so check my math here.

10 mM = .01 M

molecular weight of Calcium nitrate = 164.09 g/mol

our desired dilution = (.01)(164.09) / 1 Liter Water = 1.64g/L

Therefore add 1.64 grams of calcium nitrate powder to 1 liter of water.

My current plan:

Soak seeds overnight, refrigerated, in 10 mM solution of calcium nitrate with a little Zerotol. Strain them out and place wet into a baggie. Put baggies in the fridge until I find time to sow them…december or january…then put the seedling flats back in cold storage until April or mass germination proceedings.

I did a long warm stratification in the seedling flats last year and was generally disappointed with germination results, therefore I am giving credence to Don’s claim that warm moist stratification could cause problems. I also don’t have many species seeds going on this year.

PS, sorry to hijack your thread, Roselynn! But hopefully you are learning from their responses to my questions.

If I were you I would apply the same rigor to calculating the peroxide dilution as you do to the nitrate. Also I would start with household peroxide at 2 to 3%, just on account of how nasty the 30% is - someone I know uses it to bleach animal bones in a taxidermy shop. Those white speckles you get on your hands even with the 3% are microscopic embolisms.

Actually I would dispense with dispensing peroxide, its not beneficial at this stage.

As for baggies, I use #48790 wml 2x3 w/wht block baggies from United States Plastic. Neat labeling makes for easy management.

Just lost my message so starting again. 1 tsp/ half gal is close enough, when using the hexahydrate of calcium nitrate, which is what I have to work with. Recall that one calcium combines with two nitrates. I use 1 part by wt of vermiculite and 2 parts of solution to get moist vermiculite. Probably a similar dose would be OK with fairly dry peat, or sterile potting soil. Perlite might not hold that much liquid.

I believe it is the concentration in the liquid phase that matters. Very likely the nitrate is converted slowly to NO which is a signaling molecule stimulating germination and other things. Peroxide would interact with this in some way but I can’t predict just how. Peroxide is also know as reactive oxygen species which you can google and bring up a ton of papers.

I think you can find earlier more detailed discussions in older forum threads if you do a search back a couple years. Also it is in the RHA newsletters several times over the past 5 years.

Quite possibly nitrate watering of soils will have similar effect. For what it’s worth, the 10 mM calcium nitrate is giving a total nitrate about 1/3 higher than Hoagland’s standard plant nutrient solution designed for hydroponics back in the 1940s. Hoagland’s soln contains 5 mM potassium nitrate for the potash + N and 7.5 mM calcium nitrate for both calcium which is essential for plants, and the nitrate for N. I have used potassium nitrate successfully, but it is not quite as good as the calcium salt because it raises the salt concentration rather high to get the total 20 mM of nitrate.

Stratification almost always requires low temperatures, if not it is simply “planting” in a tiny container.

I always let my seeds sprout in the bag with about 1 oz of moist vermiculite per zip sandwich bag of 1-100 seeds. I try to combine divergent crosses together if I have very few seeds of each. I divide a batch of seeds if it is over about 100.

The newsletter has lots of examples of results. Also on the RHA website is a complete review of all documented germination studies prior to about 2010.

It is interesting to observe how similar modern methods are to those of 18th and 19th century experimenters. In the olden days, calcium was applied in the form of slaked lime. The nitrogen was introduced as “chamber lye” (urine) or ammonia. Oxygen could be in the form of “oxygenated muriatic acid gas, mixed with water” or hydrogen peroxide.

Acids also were tested, including the muriatic acid (HCl) mentioned above, and oxalic acid.

In general, the more successful methods seem (to me) to mimic what happens to seeds when they pass through the digestive tracts of animals: acid in the stomach, ammonia though the intestines, and finally atmospheric oxygen as the dung dries.

Similar conditions are met by seeds wrapped in fermenting fruit.


How are you getting ammonia in the intestines? Mammalian digestion is acidic throughout.

I should have written “colon” rather than “intestines”.

According to Wikipedia:
“A fecal pH test is one where a specimen of feces is tested for acidity in order to diagnose a medical condition. Human feces is normally alkaline. An acidic stool can indicate a digestive problem such as lactose intolerance[1] or a contagion such as E. coli or rotavirus.”

Dietary Proteins: How They Alleviate Disease and Promote Better Health
George U. Liepa - 1992
“Ammonia is produced during the catabolism of amino acids and other nitrogenous substrates. It is ultimately synthesized into urea by the liver, enters the circulatory system, and a significant fraction is excreted in the urine. However, approximately 25% of the urea enters the gastrointestinal contents by secretion or diffusion where it is hydrolyzed in the colon by bacterial ureases to ammonia and CO2. The intracolonic ammonia may be utilized by the bacterial flora for protein synthesis, absorbed and reincorporated into urea by the liver or excreted in the feces.

Most of the ammonia ends up as the carbonate:

The American Farmer, 13(10): 316 (Apr 1858)
"Estimating the nitrogen as ammonia, the yearly product of one cow is 156 lbs. of nitrogen, equal to 189 lbs. of pure ammonia, or equal to 677 lbs. of bi-carbonate of ammonia of the shops. A single cow will therefore give annually, fed on hay and potatoes, 31,035 lbs. of dung, containing
4800 lbs. of geine,
677 " of carbonate of ammonia,
71 " of bone-dust,
37 " of plaster,
37 " of chalk,
24 " of common salt,
15 " of sulphate of potash.
“It is perfectly evident from this view, that the main agricultural value depends on the ammonia, or nitrogen, and the geine. The lime, in its form of salts, goes but little way towards this value, yet valuable, so far as they exist. It is evident that the lime in the above salts of lime, the annual product of one cow, is sufficient to supply the grain and straw of a crop of 140 bushels of Rye.”

“Geine” may or may not mean humus or humic acid, depending on the author.

Rather than split hairs over this I will just contest your premise that digestion aids germination. I think that digestion, at best, is benign to germination of rose seeds and mostly I think it is detrimental. Seeds that I’ve split open that have passed through guts of birds and mammals are usually dead.

At any rate no heroics are needed to get rose seeds to germinate if they contain a healthy embryo. All you need to do is keep them moist and cold for some time and raise their temperature to a critical threshold usually around 45 - 48 degrees F. As Larry has proved, nitrate helps too.

I’d agreed that mimic nature is a good idea if its limited to the seasons.

Of course, much depends on the seed parent. I once read a story about a tomato breeder who received seeds of a tomato species from the Galapagos. He sowed the seeds in the usual way, but nothing came up. It turned out that these tomatoes are commonly eaten by tortoises. As the plants “evolved” seeds that could resist the digestive processes of the tortoise, the seeds also came to require the harsh treatment in order to germinate.

Why do roses produce edible hips if their seeds are harmed by the digestive tracts of animals that eat the hips? This applies mostly to species that are still relying on animals to spread their seeds. Cultivated roses that have been selected for easier seed germination are another matter.

Also, we should consider that the ancestors of our garden roses differ in the sorts of animals that would be involved. I don’t suppose that the tiny hips of Rosa multiflora would be adapted to passage through the gut of an elk. Nor do I suppose that a small bird could swallow a hip from R. rugosa. Some of our modern, large-flowered varieties are descended from Synstylae species with small hips, as well as from R. gigantea, some forms of which have hips the size of small apples. It is not unlikely that a given cultivar could bear large hips, but give seeds that have as little need for prolonged digestive pre-treatment as those of a multiflora.

I have read about Rosa species bearing hips that are eaten by an assortment of animals … birds as well as mammals. But so far I have not been able to find any studies regarding the effectiveness of the various animals in distributing viable seeds.

Some years back I wrote an RHA article on cowpeat and compared the processing of R bracteata seeds passing through the digestion of bovines. Turns out the cows and cowpats were major promoters of the spread of this invasive in Texas pastures. Ammonia turns to nitrate really fast in soils with nitrifying organisms which is why I chose to use nitrate. Urea goes almost as fast once some urease cleaves it. Nitrification inhibitors like N-Serve, courtesy of one of our big chemcos (Dow originally) aim to keep the ammonia bound to clay so it doesn’t turn to high nitrate that leaches away in winter rains. Whether natural soil has more ammonium or nitrate depends on a lot of things. Forests tend to be high ammonium, fields nitrate.

Roses produce far too many seeds for more than a fraction of a percent to survive even 1 year without overcrowding the environment. They are making a gamble that the losses in digestion are far outweighed by the benefits of wide distribution by traveling animals or birds. See cowpat story above to get the real dirt on this one.

Thanks for the info. I wonder which sort of animal spreads R. bracteata in its native habitat.

In San Jose, I saw hips on the Pimpinellifolias and Spinosissimas hanging on all winter. I wonder how the seeds of these species are distributed in their own homelands. Are European birds or mammals more attracted to those hips than California species?

Rosa roxburghii is the only species I’ve encountered that bears hips with a fragrance that appeals to me. I can only guess that some rodent or primate would seek them.

I don’t know what bird eats what seed, but we get flocks of robins and grosbeaks that go crazy for Tatarian honeysuckle, flowering crabapple or whatever might be hanging on in late autumn or winter as they migrate into or through our area. Red is definitely an attractant. And migration takes the seed some distance before it falls to earth. Many plants evolved for distribution by species that are long gone. For instance Osage Orange and honeylocust may have been dispersed by mammoths or other big creatures that would eat the seedlings unless they were exceedingly thorny/spiny. Notice it is only the lower branches and trunk that carries the spins on these trees. (Note, not my idea, from some magazine like Natural history a few decades ago.) Many rose hips are good eating when ripe. Canina is quite nice when soft ripe but I prefer Sunrise sunset over the others. Knock Outs are not much.