Thanks for posting that. I'm always curious about whether planting too early reduces yield even if they germinate.
Jonnys Seed has soil temperature info in it. Maybe I'll try to measure that in the future.
My experience is that in the Philly area, May 15th is the target date to plant. Odds are that even cooler than normal temps won’t last long and inhibit growth.
Of course, I usually germinate in pots indoors around the first week in April so they are ready to plant outside by mid-May.
