What Temperature Kills Tomato and Pepper Plants
Tomatoes and peppers are damaged at 32F and hurt by long cold spells below 50F. Peppers are more sensitive than tomatoes. Thresholds from Ontario, Purdue,...
Published by ThriveThyme
tomatoes peppers frost first frost
What Temperature Kills Tomato and Pepper Plants
Tomatoes and peppers are tender crops. Frost at 32F damages leaves and fruit, and a hard freeze at 28F or below kills the plants. Cold above freezing also hurts them.
The Numbers
| Temperature | Tomatoes | Peppers |
|---|---|---|
| Below 50F for days | Slows ripening and growth | Puckered leaves, stunting (chilling injury) |
| 32 to 41F | Chilling injury to leaves | Chilling injury, slowed growth |
| 32F (light frost) | Leaves and exposed fruit damaged | Often killed. Peppers are more sensitive than tomatoes |
| 28F and below (hard freeze) | Plants killed | Plants killed |
Fruit freezes at about 31 to 32F. Thawed fruit turns water-soaked and soft, so it will not ripen or store.
Sources: Ontario Ministry of Agriculture (OMAFRA), extreme temperature effects on tomato and pepper crops; Purdue Extension HO-203-W, effects of cold weather on horticultural plants; Purdue Extension frost tolerance chart.
Why the Forecast Low Is Not the Whole Story
- Frost forms on clear, still nights even when the official low is 34 to 36F, because plant leaves lose heat to the sky.
- Low spots and open beds frost first. Plants against a south wall frost last.
- Wind and clouds keep frost off. A clear, calm night after a cold front is the risky one.
What to Do Before a 32F Night
- Pick ripe and mature green tomatoes. Mature greens have a glossy, pale skin and gel around the seeds. See how to ripen green tomatoes indoors.
- Pick every pepper you want. Green peppers are edible now and will not gain much more on cold nights.
- If you want a few more weeks, cover plants before dusk with row cover or an old sheet. Lightweight row cover adds about 2F and medium weight about 4 to 6F (University of Maryland Extension). That rides out a light frost, not a hard freeze. See how to use row cover and low tunnels.
- Do not refrigerate green tomatoes. Below about 50F they ripen unevenly.
After a Frost
Check plants the next afternoon. Blackened, water-soaked leaves mean the tissue froze. If only the top leaves are hit, pick the fruit underneath right away. If stems are soft, pull the plants so disease does not overwinter in the bed.
Use the Frost Harvest Desk for your zone's frost countdown and the full list of crops to pick before 32F, and what to harvest before the first frost for the rest of the garden.