the magic 4 degrees

I’m great in asking stupid questions:

the best stratification temperature for rose seeds seems to be about 4

Hi Bernhard,

of course four is a magical number, think of the of the beatles magic mystery tour, and most garden roses have 4 sets of chromosomes (smile)

In earnest, I guess temperature requirements will differ a bit between roses of different genetic make-up; shaped by evolution under different climatic conditions. And we also know examples of roses that don’t need any cold treatment.

My rose seeds did not tolerate freezing. So, this was for me the most important lesson I learned about temperature. But there must be species roses that can withstand hard frost. Mother nature’s thermostat is not set above 0 degree Celsius.

More likely this is due to the solubility of oxygen in water which is inversly proportional to temperature; and to the activity of the enzymes that degrade abscissic acid, which are adapted cold temperatures.

it was just a thought,

thank you for the feedback, the solubility of oxygen is an interesting topic.

@Ulrike: you forgot to mention the four seasons :slight_smile:



If you want a serious answer, there are no published reports I have been able to find on any useful theories of why 4 C is the most effective temperature. But it is the one used as a standard in research labs for the water density reason mentioned (ice-water tends to settle at this temp} so biochemists have used it as a ref point for near a century. In fact some studies have been done at a series like 5, 10, 15 and as mentioned above the optimum may differ between species. I’ve found that a bit above 4 is actually better for me. I have a refrigerator set to stay a few degrees F above the normal for a home. That allows germ. in the frig from which seedlings are transplanted out as they germ.

Don has the right idea. It is about competing processes. Leaching is irrelevant. All you need is near 100 % humidity supplied by some means, and the right temp. Seeds will germ. even when not touching the wetted medium, inside a plastic bag.

We had 100% humidity with temps in the low 50’s with a low pressure system swirling around for 3-4 days this past weekend. I put my seeds outside in sand in a plastic container and I’m looking forwrd to seeing some germinations within the next week or so. This worked well for me a few years ago, I was overwhelmed with so many germinations that year.

“We had 100% humidity with temps in the low 50’s”

I assume you are speaking about 10

Hi Bernhard,

The roses that you ask about were all modern hybrid teas. Gemini, Brigadoon, Neptune and a few others. This is all I grow in my garden. I also use the refrigerator but when I want them to germinate, I’ll put them outside during a low pressure storm that comes from the south packed with lots of humidity, we get them quite often here for the jet stream carries them here up from the south especially in the spring and fall. And when the temps are in the fifty’s both day and night for a week you have a perfect combination for seed germination. I just potted up my first germinated seed today! Yeah!