What Temperature Is Too Cold for Seedlings?
Below 50°F, seedlings stop growing. Below 40°F, most are damaged. Below 32°F, they die. Here’s the temperature guide.
Tender seedlings (tomatoes, peppers, basil) are more sensitive than cool-season ones (lettuce, kale).
Temperature Guide
| Temp | Effect on Tender Seedlings | Effect on Cool-Season |
|---|---|---|
| 65-75°F | Ideal | Ideal |
| 55-65°F | Slow growth | Fine |
| 50-55°F | Stressed, purple tinge | Fine |
| 40-50°F | Growth stops | Slow |
| 32-40°F | Damage | Tolerated |
| Below 32°F | Death | Damage |
Tender vs Hardy
Tender (damaged below 50°F): Tomato, pepper, basil, zucchini, cucumber
Hardy (tolerate 40°F): Lettuce, kale, spinach, broccoli, radish
Very hardy (tolerate frost): Peas, carrots, beets
What to Do in Cold
- Move indoors if possible.
- Use a cold frame or cloche.
- Water less. Cold + wet = rot.
- Mulch soil surface.
- Cover at night with a blanket or row cover.
Common Questions
Can seedlings survive a cold night? Above 40°F, usually yes. Below 32°F, no for tender varieties.
What’s the lowest safe temperature? 50°F for tender seedlings. 40°F for hardy.
Will purple leaves recover? Yes, if it warms up within a week.
Should I bring plants inside at night? If temps drop below 50°F and they’re tender, yes.
Does wind make it worse? Yes. Wind chill can damage plants even above freezing.
How do I protect outdoor seedlings from cold? Row covers, cloches, cold frames, or moving pots inside.