When to start seeds indoors
Pick a crop, enter your average last spring frost date and get a start date. The weeks come from NC State Extension's indoor seed starting chart.
How the sources compare
Different sources give different timing, because they count different things. NC State counts weeks before the last frost. Cornell Cooperative Extension (Monroe County) gives weeks from sowing to setting plants out, using a frost-free date of 19 May as its example.
| Crop | NC State (weeks before last frost) | Cornell Monroe (weeks from sowing to setting out) |
|---|---|---|
| Tomato | 6 (8 in its germination table is for pepper and eggplant) | 6 to 8 |
| Pepper | 6 (8 in its germination table) | 6 to 14 |
| Eggplant | 6 to 8 (8 in its germination table) | 8 to 10 |
| Lettuce | 8 | 3 to 5 |
| Broccoli and cabbage | 8 | 4 to 6 |
| Onion | 10 to 12 | 6 to 8 |
| Cucumber | 4 or fewer | 3 to 4 |
What to do with the differences
- The calculator uses NC State's weeks. Where NC State gives a range, you get a window of dates.
- Oklahoma State says not to start seeds too early, to count back from your last frost date and to include about one week for hardening off. See hardening off.
- Cornell says cucumbers and squash are best started in individual plantable pots, and lists beans, beets, carrots, peas and fennel as direct sow crops.
- Seedlings kept under lights longer than needed grow tall. See leggy seedlings and how long seedlings stay under lights.
Sources
- NC State Extension, Ashe County: Indoor seed starting guide (PDF)
- Cornell Cooperative Extension, Monroe County: Starting vegetables from seed
- Oklahoma State University Extension: Tips for starting seeds at home (2025)