It appears that some varieties of roses germinate at higher temperatures than others. Last year I had one variety that I had given up up on and left the seed flats in the greenhouse. The seeds started germinating in large numbers in May when the temperatures were reaching 80-100 degrees during the day and about 50-60 degrees at night. Has anyone else seen this?
It is possible that this had nothing to do with the temperature, but that the seeds had finally overcome dormancy.
I haven’t seen that, but I live in a pretty cold region and don’t have rose seeds at that temp generally.
What do people think of this? From the seminar on seed germination Carol and Jerry Baskins led this past fall that I had the priveldge to go to it was interesting to be encouraged to think of the factors that influence germination as more quantitative. For instance, as seeds aquire more stratification, the wider the temperature range they are able to germinate at. For instance, roses seem to generally germinate better at relatively cooler temps than other plants. So, as they aquire strat. hours there comes a point when they can germinate within a relatively narrow temp range at cooler temps (? maybe 50-60F being about optimum for many roses?). As more strat hours accumulate, they can germinate over a wider temp range (fridge temps to maybe push the upper limit into the 70’sF).
Shane, perhaps something like this may have happened. Your seeds had low dormancy and the widest temp range possible for germ to occur and they germinated at higher temperatures. It seems like secondary dormancy comes at some point in roses where after reaching warm temps they aquire dormancy factors again and need stratification to once again release them. Perhaps your seeds escaped that. What background do these roses have? Are they hardy species or crosses of relatively tender parents that prefer warmer climates?
You would probably be interested to know that the rose I am referring to is Bayse Blueberry. If the records are correct, Bayse Blueberry has R. Virginiana and R. Carolina in its ancestry which are both native to the colder areas of the country. That makes the germination in higher temps even more odd.
After 2 months stratification last year, the Bayse Blueberry seeds had no germination for about 4 months, 2 months in the basement and 2 months in the greenhouse. Just when all my other roses stopped germinating because of the heat, Bayse Blueberry started germinating. I was baffled.
This year, I am going to give Bayse Blueberry seeds a much longer stratification time (possibly 4 months) and see if it speeds up germination time.
Thanks for the information on longer stratification times!
Wow Shane, that’s interesting. I have a BB and it’s been completely cane hardy here in MN/WI (Z4) the past couple years. I’ve had poor germination with it as a female, but you inspired me not to give up so soon on it.
Or could this somehow be a rose’s homage to the seed parent’s origin at Texas A&M where those hot temperatures arrive early in spring (compared to the rest of the USA)?
I will let you know how the longer stratification turns out. I am still reluctant to use it as a seed parent in large numbers because I am not quite sure if I can replicate last year’s conditions, but hopefully the longer stratification works out.
That is interesting about the Texas conditions. Rosa Carolina is native to warmer climates like Texas and Florida so maybe that has something to do with it.