How cold can tomato plants tolerate might be one of your questions if you’re a novice to growing tomatoes.
Tomatoes do not like to be cold, yet they actually endure and try to survive chilly temperatures to some degree. However, the plants grow best in warmer areas, particularly at higher temperatures.
Tomatoes have specific growing requirements. These plants need full sun and rich soil. At night, they prefer temperatures ranging between 59 to 68°F while they prefer 70 to 85°F during the day.
However, tomato plants are known to survive temperatures at 33°F. It is when the temperatures drop below 50°F and the plants are not protected, that tomatoes will start to indicate several growth problems.
All About Tomato Plants and Temperature
The tomato is one of the most popular home garden vegetables to grow. This plant comes in several varieties, and some favorites are heirloom and cherry in various sizes and colors.
Tomato seedlings prefer a temperature between 58 to 60°F while inside the greenhouse. And they should not be transplanted until the threat of the last frost has passed.
The plants’ tolerance, both for extreme heat or cold, matters when it comes to the development of blossoms and setting fruits.
However, temperature tolerance varies upon cultivars and some other factors. Even in the spring, when daytime temperatures are too warm and nighttime temperatures fall below 55°F, blossoms drop may likely occur.
Low Temperature and Tomatoes
Low temperatures at night inhibit tomato plants from converting sunlight into sugar through photosynthesis.
When the temperatures drop below 50°F at 10 p.m during the night and do not warm up until 8 a.m the next morning, your tomatoes will behave as if it were still night. The plants will continue those nighttime activities even during daylight hours.
And what makes it worse, the plant will initiate daytime activities competing with this ongoing nighttime process and will start turning the plant’s starch into sugars.
In addition, this contributes to the fruit deformation, scars, and cracks on the fruit blossom end. This usually happens when the temperature at night drops down below 60°F.
Donald Ort, a plant physiologist at Urbana, said, “Plants have an inborn timekeeping mechanism—a circadian rhythm played out over 24 hours—during which specific chemical reactions take place.”
The warm weather, which is the evolutionary origins of plants like tomatoes, make the plants more sensitive to changes in temperature during the growing season.
And according to Ort, the circadian rhythms regulate the timing of processes within the plant. “There are specific reactions that are timed to occur at a given period of day or night,” he adds.
And when it happens at the same time, they will compete and delay the process of photosynthesis, which may likely paralyze a runner.
High Temperature and Tomatoes
In summer, tomato plants lose significant numbers of immature fruits and flowers when the temperature consistently rises to 90°F during the day and 76°F at night.
Like us, tomatoes suffer when the surrounding temperature is too hot. And the energy to set fruit or growth will be used to cope with the hot temperatures.
Heat stress forces tomato plants to increase transpiration to survive. This usually happens when extreme heat continues for extended periods.
And too warm temperatures can make tomato pollen grains to begin to burst, further thwarting pollination and resulting in no fruit set. This usually happens when the air is significantly humid.
While exposure to extreme weather temperatures can cause significant damages to the plants, providing shade covers or the colder weather can subside damages caused by high temperatures.
5 Tips How To Protect Tomato Plants on Cold Nights
Tomatoes have specific growth requirements. And when it comes to climate, this plant does best with full sun, rich soil, and a constant supply of moisture.
But not all tomato growers live in areas with warm climates. And knowing how cold is too cold for tomatoes will help the plant to flourish even in your cold weather conditions.
So, if you’re considering growing tomatoes and getting the best out of the crop, make sure to provide the plant with proper growing needs.
When the soil temperature exceeds 60ºF during the day, tomato roots can retain heat and survive, even when the night is cold.
And the application of mulch around your tomatoes will help retain the heat during the day. It will help tomato plants survive from a cold snap or a series of cold nights.
However, the plant’s survival on cold nights and growth are two separate matters. How tomato plants survive through cold also depends on how the plants acclimate to cold, wind, and the fluctuating weather conditions.
Tomatoes can tolerate 56.3ºF nighttime temperature, but when the temperature falls between 32 and 41°F, plants are susceptible to chilling injury. Chilling injury can cause wilting, necrosis of foliage, and make tomatoes prone to diseases.
And when the daytime temperature falls below 50ºF for a few days, the low soil temperature will prevent root development. It will interfere with pollination when the plant starts to bloom, which may likely result in an inferior fruit.
However, there are a few techniques you can practice to protect your tomatoes from cold weather and continue to harvest fresh tomatoes even until autumn.
Use Thermometer to Monitor Actual Air Temperature
Depending on the area where you live, your tomato garden has a microclimate, and your local forecast might differ from the actual temperature that is taking place in your garden.
The use of a thermometer to monitor the actual level of the air temperature will help avoid the possibility of damages due to the cold impact on your tomato plants.
Protect Tomato Plants with Frost Cloths
When the frost is in the forecast overnight, protect your tomato plants with lightweight frost cloths. And when you’re expecting an extended cold pattern, considering quality frost protection will help ensure a fresh harvest.
Use hoops or drive several stakes into the ground around your tomato plants as a frame for your frost blanket. But make sure to add 2 feet more to the height of your tallest plant when determining the length of the stakes or hoops.
The additional length will provide clearance above the tall plants and allow you to drive the stakes or hoops sturdily into the ground.
As you lay the frost cloth in the garden, ensure the top and all sides are covered. And secure it with bricks, large stones, ground staples, or tent pegs.
However, don’t forget to remove the frost cover the next morning. This way, tomato plants can bask in the sun.
Use Christmas Lights to Add Warmth at Night
Clipping Christmas lights to the support of your tomato plant or installing them under the hoops is another way to supplement heat and help the plant survive on cold nights.
The use of an old incandescent variety of bulbs to generate subtle yet adequate heat will help warm your plant on cold nights.
Unlike LEDs, these types of bulbs can raise the temperature by 2 to 10°F when placed under the frost blanket.
However, make sure bulbs are not in contact with the plant foliage or the frost cover fabrics to avoid accidents and future problems.
Toss a generous layer of mulch around the plants to help insulate the soil and retain accumulated heat during the day.
But make sure to add the mulch around the plants before a cold snap. Add about 6 inches deep in your tomato patch and leave an inch from the central stalk of your tomato.
An inch space provided in the base of your plant will allow the heat from the soil to radiate upwards through the plant.
But when the weather starts to warm up in spring, make sure to pull out a few layers of the mulch so that the ground receives sunlight and warmth.
Water Plants Before a Night of Frost
Giving your tomato plant a good drink before the frost at night allows the soil to radiate a warming effect on a cold night.
Usually, as the water freezes at night, it releases heat that warms the plant cells and helps reduce the chance of plants freezing, making the tomatoes frost-free, though the surrounding becomes frosty.
But make sure not to water the plant foliage to avoid the possibility of foliar diseases in your tomatoes.
You can also fill up several one-gallon jugs with water and screw on the cap. Draw these jugs into the soil next to your tomato plants, in a spot where they receive and will warm up in the sunshine.
The water in the jugs absorbs heat during the day and will slowly emit at night, warming the air around your plants.
This technique is especially helpful within a greenhouse, tunnel, or under a cold frame. It lifts the temperature inside to some degree and helps young plants survive on cold nights.
How To Grow Tomato Plants In Cold Climates
Tomatoes are summer crops that can die when exposed to extreme cold, which is why growing and getting them ripened requires an adequate amount of heat.
When the temperatures at night drop below 50°F, tomato plants will start to feel cold and shivers. So growing tomatoes in the greenhouse may likely be easier to achieve ripe tomatoes than growing the plant outdoors.
However, there are a few tips you can follow to harvest lush and juicy tomatoes, even if you’re a Northern grower with no greenhouse structure to grow tomatoes.
1) Choose a Hardy Variety
There are several varieties of tomatoes in the market today. However, even the most cold-hardy varieties are heat-lovers at heart.
But some tomatoes such as Glacier and Sub Arctic Plenty set well with cold weather and shorter days. These varieties can tolerate cold weather better than others.
Generally, determinate or dwarf tomatoes do well for outdoor growing and are best suited for novice gardeners.
They grow up to 4 feet tall only and do not require staking when grown in pots, while indeterminate tomatoes grow until frost and can get up to 8 feet tall.
So, make sure to get a variety that adapts quickly to the weather where you live to grow and produce better yields.
2) Grow Them In Pots
Of course, you can grow your tomatoes either directly into the soil in your garden or in some container pots. However, growing winter tomatoes in container pots perform better than in the garden bed.
And if you’re growing tomatoes when most of the nights are cold, the ones in container pots will give you the option to move the plants around to anywhere else that will provide heat to the bottom.
You can move them inside the garage to protect from the frost and bring back outdoors the next morning to bask in the sun.
3) Water The Plant Regularly
Frequently watering your tomato plant is essential, particularly with tender young plants. If you neglect to provide water and suddenly try to catch up on the watering, this can cause skin cracks.
The crack or skin splitting can cause moisture loss in the fruits, and you’ll end up with tomatoes that are not lush and juicy.
Besides, when the cracks occur in green tomatoes, the fruits will likely rot before they fully ripen while hanging on the vine.
4) Feed Tomatoes Accordingly
Tomatoes do well when fed with organic and enriched fertilizer, like compost, particularly when the plants start to bloom. You’ll want to replenish lost nutrients after the plants fruit.
5) Support Your Tomato Plants with Stakes
Tomato plants are naturally floppy and require support when they start to grow tall and begin to bloom.
And when your plants start to set fruit, providing them with stakes to support the stalks secured with ties is essential. Tomatoes left to droop and lie on the ground are prone to diseases, producing inferior fruits.
You can either use canes, wires, or cages to keep them upright and save branches from splitting due to the weight of the fruits.
6) Remove Suckers
A sucker in the tomato plant is a secondary stem that forms in the axils of side branches, and when left to grow, will also produce both flowers and fruits.
The plant with suckers unpruned produces more fruits with smaller sizes. But if you’re aiming to harvest with larger fruits, remove all the suckers that grow below the first flower cluster. This will help keep the main stem sturdy and will eventually produce fruit in bigger sizes.
Also, removing suckers will allow the plant to better attach to the stake. This will prevent branches from sprawling down to the ground.
And if you’re using a single stake, you would like to keep only the main stem and remove the others to ensure the plant stays upright.
Removal of tomato suckers will also allow air and light to penetrate the plant and prevent diseases. The plant becomes more manageable and robust. But when the plant is too dense and bushy, it makes the plant prone to pest infestation.
So the reason behind pruning tomato suckers depends on what goal you have in mind. It’s up to you to decide whether you want to remove the plant’s secondary stems or not.
Prune the suckers if you want bigger but fewer tomato fruits or leave them to grow if you wish for more numerous fruits but the harvest comes in slightly smaller sizes.
Tomatoes are versatile fruits that grows best in warm weather with a steady supply of moisture, but are also one of the most sensitive to the cold of all summer vegetables.
Although mature plants can survive light frosts, temperatures below 40°F can damage the plant’s flower and fruit production.
However, providing your tomatoes with frost covers with warm air can save the plants from aborting flowers and fruits.
The air will circulate inside to help them survive during the cold nights when the temperature is too cold for the plants to handle.
Aside from providing shelter through frost blankets, adding supplemental heat through light sources, whether in a greenhouse, low tunnels, and frost blankets will keep the soil warm the whole night.
Water jugs around the plants can also help accumulate heat during the day and gradually radiate at night, helping extend tomato production even during minor frost or cold fall nights.
And adding a generous layer of mulch to the base of your tomato plant is also helpful to retain heat from the soil. This helps make tomatoes frost-free by releasing the heat that warms the plant cells, although the surrounding environment is frosty.
Gardeners who have a greenhouse are fortunate enough to bring in their tomato plants before the first frost and will have ripened tomatoes late in the autumn.
But not having a greenhouse won’t hinder you from having ripe tomatoes in the fall.
When you know how cold your tomatoes can tolerate and how to provide them warmth when the temperature drops, your tomatoes will surely survive even during prolonged cold nights.