How long do seedlings stay under lights?
From 3 to 4 weeks for cucumbers and squash to 6 to 14 weeks for peppers, according to Cornell Cooperative Extension.
Weeks from sowing to setting out (Cornell Monroe)
| Crop | Weeks |
|---|---|
| Parsley | 9 to 10 |
| Leeks and onions | 6 to 8 |
| Collards, kale, spinach | 4 to 6 |
| Peppers | 6 to 14 |
| Arugula, lettuce | 3 to 5 |
| Broccoli, cabbage, chard | 4 to 6 |
| Tomatoes | 6 to 8 |
| Eggplant | 8 to 10 |
| Basil | 6 |
| Cucumbers | 3 to 4 |
| Pumpkin, squash | 3 to 4 |
What it means for the shelf
- A shelf with tomatoes, peppers and eggplant stays busy for 6 to 14 weeks. A shelf of lettuce turns over in 3 to 5.
- Running cost scales with weeks. 80 W for 14 hours a day over 10 weeks is 78.4 kWh, the same as the default in the calculator. See running cost.
- Seedlings kept under lights past the right size need more space and more height. See hanging height.
- Counting back from your last frost date for sowing dates: frost-date calculator.