How much cold can tomatoes tolerate? Tomatoes are notoriously cold-sensitive, so it helps to know what to do with the plants when temperatures drop. Your tomato plants may still have unripened or partially ripened fruit on them when the thermometer plummets to the freezing mark. Learn how to protect your tomato plants when the cold weather moves in.
As a tomato gardener I know how exciting it is to see those sunny red globes ripening on the vine. But I’ve also experienced the heartbreak of losing my hard work to an unexpected spring or fall frost. If you want to protect your tomato crop it’s crucial to know when to cover your plants at night.
In this complete guide, we’ll dive into everything you need to know about covering tomatoes after dark. I’ll share tips on optimal temperatures, signs of cold damage, types of covers to use, and when it’s safe to uncover your plants. Let’s grow some happy, healthy tomatoes!
Why Tomato Plants Need Protection from the Cold
Tomatoes thrive in warm conditions The ideal temperature range for growth and fruit production is 70-85°F during the day and 55-70°F at night Once the mercury dips below 50°F, tomato plants suffer damage.
Chilly nights negatively affect pollen production, fertilization, and fruit set. Photosynthesis also dramatically decreases, resulting in stunted growth. Temperatures below 40°F can be fatal, especially for young transplants. Even light frosts in the low 30s will decimate your tomato crop.
Mature plants have a higher cold tolerance than seedlings. But prolonged exposure to temperatures under 50°F will still hinder yields. Bottom line: consistent cold spells spell trouble for your tomatoes.
Recognizing Signs of Cold Injury
It’s easy to diagnose cold damage in tomato plants. Watch for these telltale symptoms:
- Wilted, curled leaves that don’t recover during the day
- Purple, bronze discoloration on foliage
- Increased disease susceptibility
- Flower drop and poor fruit set
- Small, misshapen tomatoes
- Split stems and cracked fruit (catfacing)
At the first sign of any cold stress, it’s go time for emergency covers. Don’t delay or the cold could quickly kill your crop.
When to Deploy Plant Covers
Many gardeners debate the ideal temperature threshold for covering tomatoes. Some say 50°F, others wait for 40°F. Here are my guidelines:
- Cover plants when lows are forecast between 40-45°F
- Definitely cover any night below 40°F
- For best results, add covers before sundown to conserve residual heat
- Remove covers after sunrise once temps climb above 40°F
I also watch long range forecasts. Be ready to cover plants anytime cold looms, even if not imminent. It’s better to be safe than sorry with your tomato babies.
Types of Covers to Use
You have several options when it comes to barrier methods for shielding your tomatoes from the cold. Here are some of the most popular:
Row Covers
These lightweight breathable fabrics drape directly over plants, trapping heat while allowing air and light through. Look for covers rated to at least 25-30°F. Use hoops to prevent the material from touching plants.
Hot Caps
Individual plastic domes fit over plants, increasing temps by 5-10°F. Remember to ventilate on sunny days. Remove caps once lows are reliably above 50°F.
Cloches
Bell-shaped glass or plastic shields that surround plants, boosting temps by up to 20°F! Vent cloches during the day and remove after all frost danger has passed.
Wall O’Waters
These plastic water-filled rings encircle plants, providing insulation against cold. Especially great for giving young transplants an early season boost.
When to Stop Covering Tomato Plants
Once nightly lows consistently remain above 50°F, normally 4-6 weeks after the last expected frost, it’s safe to leave tomato plants uncovered. But keep watching the extended forecasts for any unusual cold fronts. I often have to scramble to cover my tomatoes even in late spring when freak frosts strike.
If your plants do experience some chilly nights in the 40s, don’t panic. Mature tomatoes can handle a little cold shock as long as it’s not prolonged. Just be vigilant and ready to protect your crop anytime cold looms in the outlook.
Tips for Successful Tomato Covering
Follow these tips for the best results when covering your tomato plants:
- Wait to transplant until soil has warmed and nightly lows reach 50°F
- Harden off transplants for 7-10 days before planting out
- Add covers before sundown to retain residual heat
- Use supports to keep fabric off plant leaves
- Monitor forecasts and cover plants anytime lows near 40°F
- Remove covers during the day to prevent overheating
- Stop covering after 4-6 weeks of consistent lows above 50°F
- Mulch around plants to insulate roots and retain heat
- Water well before draping covers to prevent moisture loss
With the right covers and timing, you can protect your tomato crop from cold damage and extend your harvest season. Just be diligent and don’t hesitate to cover your plants whenever chilly weather strikes. The extra effort will reward you with a bountiful tomato crop lasting from early summer through late fall.
Select Early- or Mid-Season Tomatoes
Choose cold-tolerant tomato varieties bred to set fruit in cooler temperatures below 55 degrees Fahrenheit. These varieties typically also mature earlier.
Early-season varieties mature in 52 to 70 days and mid-season tomatoes in around 70 to 80 days. There are many different varieties, both hybrid tomatoes and heirloom tomatoes. Popular varieties include Early Girl (52 days) and Better Boy (75 days).
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The Spruce / Steven Merkel
Start Tomato Seeds at the Right Time
Prevent cold damage by starting your tomato plants from seed indoors at the right time. If you start the seeds too early it will still be too cold to move them outdoors. Its best to start tomatoes from seeds six to eight weeks before your area’s last projected frost date.
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Protecting Tomatoes from Freezing Temperatures
FAQ
How cold is too cold for tomato plants at night?
Another temperature to keep in mind: tomato plants will not survive in temperatures below 35 degrees Fahrenheit, and will not thrive at temperatures below 50 …Sep 7, 2023
At what temperature do tomatoes need to be covered?
Tomatoes are tender. They can handle temperatures in the 40s (Fahrenheit) but they are not best pleased. Once it gets into the high 30s I cover them.May 24, 2023
When can you leave tomato plants out overnight?
You don’t leave them outside at night unless it’s a few weeks past their typical last frost date, and at least 10C at night. Also, since your tomatoes are greenhouse-grown, they need to be gradually hardened off.
Can You cover tomatoes at night?
Once nighttime temperatures consistently stay above 50 degrees Fahrenheit, it is safe to discontinue covering your tomato plants at night. How many cups are in 32 ounces?
Are tomatoes still good to eat after a frost?
Yes. However, if the tomatoes have frozen even a little, it’s advisable not to eat them raw since the texture of the fresh tomato will have changed significantly when thawed. You can either cook them immediately after picking or place them in the freezer, whole, diced, or mashed, to use for cooking at a later period.
When should you cover tomato plants?
You want to cover the plants when temperatures are expected to be between 40 and 50 degrees F during the day and 20 to 30 degrees F at night. If you expect low temperatures much lower than this, it’s best to harvest the fruit. Tomatoes don’t like cold weather, although they can survive during short cold snaps.
What temperature should tomato plants be covered at night?
Tomato plants are particularly susceptible to frost damage, and the ideal temperature range for their growth lies between 55 to 85 degrees Fahrenheit. The best time to cover tomato plants at night is when the temperature is expected to drop below 50 degrees Fahrenheit.
How do you keep tomato plants warm at night?
Using fabric or pest-proof mesh cloth which will allow more air circulation. Alternatively, you may like to grow your tomato plants in a greenhouse. This will keep them warm at night. You can also put a layer of mulch around the bottom of your tomato plants to help keep the roots warmer during the night.
How long should tomato plants be covered in autumn?
Although tomato plants start out pint-sized, by autumn they can be absolutely massive – especially if they are of the indeterminate variety! To keep your tomato plants productive for as long into autumn as possible, they will need to be covered up each evening when temperatures dip below 50°F (10°C).