butternuts locally sourced in zone 3

butternuts locally sourced in zone 3. first time growing, I find they take their time or just wait for warm weather to germinate. these are 4-8 weeks out of stratification in the greenhouse, just now steadily germinating. slower than the buartnut and japanese walnut, at least from these seed sources this year. my black walnut are also still coming up. anyone else find the same?