My dad said to plant tomatoes after Mother's Day in Denver, and I ignored him for 3 springs | Backyard Living - Freelance Forum - The Community for Independent Professionals
My buddy did the same thing for four years straight up in Fort Collins. Every May he'd get impatient and shove them in the ground, then we'd get one of those freak late snows and he'd be out there at 6am draping sheets over sad little black stems. Last year he finally waited until the middle of May and ended up with more tomatoes than he knew what to do with. His kid was selling them at a card table by the road. So yeah, your dad was right, and that hurts more than the frost.