Go to the wintersowing forum here on GW. It is a method that uses the natural process, but with added protection to prevent erosion or animals eating the seeds. The containers also help maintain a more consistent moisture level to maximize germination. I've wintersown for many years and have excellent results every time.

Martha

The info that caterwallin showed on your other thread from Prairie Moon is good, they also list a simple 60 days of cold as an option too. I have also seen 90 days cold stratification listed elsewhere. If I recall since I got my seeds in February during a warmer winter, I tried some in the fridge for 60+ days in a baggie in damp potting mix and then moved them to a wintersowing container outdoors. I also wintersowed some directly outdoors in February, but I think the fridge ones were the ones that germinated.

I imagine that if I have left out the non-germinating seeds to go through the full cold-warm-cold-warm cycle that caterwallin mentioned, more would have germinated the next spring. But I potted up my two seedlings and in the process either buried or discarded those non-germinated seeds. There are good instructions for germinating a lot of native seeds at Prairie Moon.

I got the seeds today and put the Ptelea trioliata in a plastic bag with moist soil. It says for sixty days, Could I take them out a month early, instead or sixty just thirty?

If you have enough seeds, you could try both. Also maybe keep some to try the full cold, warm, cold , warm cycle. That would increase your chance for success overall probably. It don't think 60 days would be too far along in my zone, and you are farther north. We often still have snow well into April. As long as you keep any new seedlings well watered and in light shade, they should make it through the heat of summer well.