How it works
We find your average last spring frost from NOAA climate normals, then apply Purdue Extension's timing for four groups of vegetables:
- Hardy (asparagus, broccoli, cabbage, kale, onion, peas, potato, radish, spinach and more): 4 to 6 weeks before the last frost.
- Semi-hardy (beet, carrot, cauliflower, chard, lettuce, parsnip and more): 2 to 4 weeks before.
- Tender (bean, sweet corn, tomato): after the last frost, once nights stay above 50°F.
- Very tender (cucumber, eggplant, melons, okra, pepper, pumpkin, squash, sweet potato): at least 2 weeks after the last frost, once nights stay above 60 to 65°F.
Purdue wrote these rules for Indiana, but because they count from your own frost date they work as a starting point anywhere with a frost season. Check seed packets for each variety.
Sources: Purdue Extension, "Indiana Vegetable Planting Calendar" (HO-186-W, December 2020); NOAA National Centers for Environmental Information, U.S. Climate Normals 1991-2020 (annual/seasonal freeze probabilities).