Flower Seed Packet
I purchased New York Ironwood seeds from the gift shop at Mount Vernon. On the back panel it talks about seeds requiring cold treatment. What does that mean?
Some seeds need a period of chill/cold, called stratification, to improve germination.
This would mimic our winter period.
You can do this artificially by putting the seed packet in a zip lock bag and storing it in your refrigerator for a minimum of 2-3 months.
We find this page from the Ladybird Johnson Wildflower Center helpful: