Stratification Temperature

I have some rose seeds I’ve just potted up. Last year, about this same time, I put the pots outdoors to stratify. The pots pretty much froze solid immediately and stayed that way for a substantial amount of time – missing out on any warm-moist period or even the fairly cold (but not freezing) period of fall. I got some germinations but I’m wondering if I could do better.

So, right now I’ve got the pots sitting in my parents’ sunroom which is only partially heated. The temperature out there right now is 45 degrees F (6-7 degrees Celsius); outside the ground has been frozen all day. What I’m wondering is, is this cold enough?

Great questions Tom. When things are frozen the accumulation of stratification hours tend to cease because cellular metabolism supposedly “stops”. George Mander has talked about the benefit of fluxuating cooler temps for germination. I have found better germination among polyanthas when I have the seeds in a fridge that is 40-45F rather than 34F where they tend to rot, but 34F is great for all my other crosses and seems to give me better germination for those seeds.