Will Frost Kill Tomato Plants? Protecting Plants from Cold Damage

For gardeners in cooler climates the threat of frost always looms over tender warm-season crops like tomatoes peppers, and eggplants. A killing frost can swiftly wipe out unprotected plants before the growing season has reached its peak.

So how cold is too cold for tomato plants? And what can you do to help tomato plants survive early autumn frosts when there’s still abundant green fruit on the vine? Read on to learn how tomato plants handle cold temperatures and methods for protecting your crop

How Cold is Too Cold for Tomato Plants?

Tomato plants are very sensitive to cold conditions. Here are the key temperature thresholds to know:

• Below 50°F – Temperatures dipping below 50°F start to negatively impact flavor development and ripening of existing fruit.

• 40°F – Prolonged chill below 40°F causes unripe green tomatoes to decay and rot rather than ripening.

• 33°F – Brief exposure to temperatures as low as 33°F can be tolerated by plants, but prolonged cold causes damage.

• 28°F – A light frost of around 28°F will damage plants down to ground level. Fruit is still salvageable if protected.

• 25°F – Hard freeze below 25°F will kill the entire plant including roots and all fruit.

So in essence, tomato plants stop thriving below 50°F and progressively sustain more cold injury as temperatures drop lower. Any frost or freeze will finish off unprotected plants.

Signs of Frost Damage on Tomatoes

Watch for these visible signs that your tomato plants have been impacted by cold autumn temperatures:

• Wilting, drooping leaves
• Leaves turn yellow, then brown and shrivel
• Stems and branches appear limp or blackened
• Unripe green tomatoes develop blemishes or soft spots

If daytime warming doesn’t revive plants and new growth stops, cold injury has likely occurred. Time to take action to prevent further damage.

Protecting Tomato Plants from Frost

When frost threatens, there are steps you can take to shield your tomato crop:

• Harvest ripe and partly ripe fruit – Pick all mature tomatoes to ripen indoors 1-2 weeks before your average first frost date.

• Cover plants – Drape plants with frost blankets, drop cloths, or tarps at night if frost is expected. Remove coverings daily.

• Provide insulation – Surround stems with dry leaves, straw, or other insulating materials. Avoid direct contact with foliage.

• Add warmth – Position strings of outdoor holiday lights under plant covers to provide radiant heat.

• Water well – Moist soil retains more warmth than dry soil. Water a day or two before a cold night.

• Select varieties wisely – Some tomato cultivars have greater cold tolerance than others. Choose early and late-season types.

With some TLC and protection, your tomato plants can make it through those first few frosty nights of fall. Just be ready to take more drastic measures if extreme cold settles in.

What to Do if Frost Kills Tomato Plants

If frost damage is severe and plants stop producing new growth, it’s time to cut your losses. Here’s how to handle a garden after a hard frost:

• Yank out dead plants – Pull up and discard any obviously dead tomato plants to prevent disease issues.

• Search for survivors – Some root systems may still be alive. Mound soil over roots and mulch to insulate. New shoots may emerge if the soil stays warm.

• Harvest all fruit – Pick any remaining fruit, ripe or green, and move indoors to allow it to slowly ripen. Discard any with soft spots.

• Clean up debris – Remove all dead vines and fallen fruit, disposing of disease plant material. This minimizes overwintering inoculum.

• Plant a cover crop – Sow cereal rye or clover into vacant garden spaces. The roots improve soil structure and prevent erosion.

With emergency measures, you can make the best of a too-short tomato season. And the garden cleanup gives you a head start on preparation for next year’s crop.

How to Keep Tomato Plants Warm in Cold Weather

When chilly autumn nights arrive but you’re not quite ready to say goodbye to those homegrown tomatoes, consider these options for adding warmth and extending the harvest:

• Build mini hoop tunnels over plants using PVC pipe and greenhouse plastic. Remove during daytime.

• Line raised bed walls with black landscape fabric. The heat-absorbing color helps retain warmth around plants.

• Sprinkle mature compost into the garden bed. The microbial activity releases heat.

• Switch to determinate tomato varieties that complete fruiting earlier before cold sets in.

• Plant in large containers that can be moved into a garage or unheated patio on frigid nights.

With creative strategies, you can keep those tomato plants cozy even when temperatures drop. Enjoy garden-ripe tomatoes long into the fall season with a little extra TLC.

Frequently Asked Questions About Frost and Tomato Plants

If you’re wondering how to maximize your tomato harvest into the colder months, here are answers to some common questions:

What temperature can tomato plants tolerate at night?

Ideal nighttime temperatures for tomatoes are above 55°F. Growth declines below 50°F and plants suffer damage below 40°F.

Do tomato plants stop producing in cold weather?

Cooler fall temperatures normally slow production. But protect plants from frost and chilly nights to extend the harvest as long as possible.

Will frost kill tomato plants overnight?

A light frost (around 30°F) can kill above-ground growth but root systems may survive to resprout. Hard freezes below 25°F kill the entire plant.

Can you keep tomato plants warm in winter?

In very mild winter climates, plants can be kept alive through winter with protection like mini-tunnels. But most gardeners treat them as one-season annuals.

Should you cut down tomato plants after frost?

It’s best to remove dead frost-damaged plants to prevent diseases. But if roots survive, mound soil over them to insulate and see if new shoots appear.

Arm yourself with knowledge about how to keep those tomato plants healthy even when cooler weather threatens. With the right techniques, you can enjoy ripe tomatoes right up until final fall frost.