the USDA plant hardiness zone map will tell you what zone you are in. If temperatures in the 25 to 28°F (-4 to -2°C) are predicted, expect a hard “freeze” which is widely destructive to most vegetation. Cloudy skies: you may be in luck. check out my article on when it is too late to plant tomatoes. If a period of unseasonable cold is approaching, keep the tomato seedlings indoors for a little longer before transplanting outside. Instead, prolonged exposure to this temperature will cause chilling injury, reducing the vigor of the plant. learn more about catfacing and other common tomato deformities, along with what causes them, in my article here. Let's solve your gardening problems, spend more time growing, and get the best harvest every year! The Farmer’s Almanac has a tool that you can use to find the dates for your region. You can learn more about cloches and how to use them in my article here. If the weather calls for an extended period of temperatures at 40 degrees Fahrenheit, it might be a good idea to harvest your fruit. You can prevent poor pollination by keeping your tomato plants just a bit warmer.  You can do this with row covers (more on this later). Chilling injury occurs in tomato fruit if they experience temperatures of 10 ° C for longer than 14 days or temperatures of 5 ° C for more than 6 to 8 days. For instance, say the last frost date in my areas is May 9, and I would like to start my tomato seeds indoors 6 weeks (6×7 = 42 days) before then. Once summer heat arrives, the plants will recover fully. For that reason, you should plant to track short-range and long-range weather forecasts for your area. Any temperature below 55 degrees Fahrenheit will cause dropped flowers and decreased fruit quality. For more information, check out my article on when it is too late to plant tomatoes. Tomato plants will survive temperatures down to freezing, so a low temperature of 35 degrees will not kill them. A greenhouse is more than capable of generating stifling hot temperatures on sunny days, so keep an eye out. The plant will also be less hardy and more susceptible to disease. It’s worth noting that in a hoophouse plants can tolerate lower temperatures than those listed here: they have the pleasant daytime conditions in which to recover. What Is the Coldest Temperature Tomato Plants Can Handle? The frost dates are usually fairly reliable. You can learn more about hardening off seedlings in my article here. They all prefer temperatures of about 60 degrees and above during the day but really become vibrant in temps of 70–95 degrees. For tomato seeds, the soil temperature needs to be 50 to 95 degrees Fahrenheit to achieve germination (65 to 85 degrees Fahrenheit is ideal). Planting earlier than this would be much better for my harvest. The longer a tomato plant is exposed to cold temperatures, the worse the effects will be. Adding cloches to cover young plants can provide even more cold protection (more on this later). Otherwise, you might lose your tomato plants on a single cold night! Every year, gardeners get excited to start their tomato plants, in the hopes of a great harvest. Insulate the plant with sheets or cloches if frost threatens. You can find the last frost dates using this map from the Farmer’s Almanac. Containers to Plant the Seeds. Tomato temperature tolerance for extreme heat or cold snaps is of extreme importance to the development of blossoms and subsequent fruit set. This will decrease the plant’s hardiness, making it … In the summer when temperatures soar over 90 F. (32 C.) with nights over 76 F. (24 C.); again, the tomato plant will suffer damage to immature fruit or loss of flowers. learn more about Glacier tomatoes on the Reimer Seeds website. Frost damage can occur when temperatures dip to or below the freezing point, 32 degrees Fahrenheit (0 degrees Celsius). So, I will want to harvest all of my tomatoes by October 3rd. A temperature of 32 degrees Fahrenheit or below will result in frost that will kill unprotected tomato plants. According to the University of Illinois Extension, the texture and flavor of the fruit will decline at these temperature. So, if you want larger tomatoes, you might need to build a greenhouse! A freeze or frost is when the nighttime temperature is between 28-32 degrees F. There’s also what’s known as a hard or killing frost which is more severe. Remember: the soil temperature should be kept at 65 to 85 degrees Fahrenheit for ideal tomato seed germination. Whether you use tarps or stakes, you will need to weigh down the edges so that the wind doesn’t blow them out of place. However, they are only an average. Another way is to bend a flexible plastic rod into a half-circle. Maintaining a temperature of 16.7 degrees Celsius (62 degrees Fahrenheit) at night is critical during pollination. A fast-maturing tomato variety will ripen faster and be … However, it will not kill them directly. This means that the plants will be indoors for 8 to 10 weeks total. However, a cloche is a great way to keep plants warm if they are transplanted early in the season, or if unexpected cold comes to your area. Allow the plant to warm and thaw throughout the next day without touching it. Some cold frames open automatically when the temperature gets high enough, and then close again when it gets low enough. Otherwise, you won’t be able to trap heat underneath the covers, and there won’t be much benefit to your plants. Not only is it rewarding to pick your own fresh produce, but once picked, lettuce will continue to grow, giving you successive harvests of fresh greens. Tomato plants will survive temperatures down to freezing, so a low temperature of 35 degrees will not kill them. If you live in an area with a short growing season, there might not be time for cold treatment. What you use will depend on whether you want to suppress the growth of weeds in a garden or improve the appearance of your yard.So, what are... link to Types of Arbors (Dozens Of Styles and Materials), link to Alternatives To Wood Mulch (12 Options With Pros & Cons), illustration of ideal temperature ranges for tomato plants here. If you put tomato seedlings near a window, make sure they don’t get a cold draft from a leaky window. And both cold-hardy plants and tenderer plants that do best in warmer temperatures can, depending on the circumstances, be affected by frost damage. Every so often, a year with strange weather patterns will bring spring frosts much later than average. There’s the best temperature for germination and then another best temperature for growing. Here are a few cold-tolerant tomato varieties: If you would rather stay ahead of the cold by growing your tomatoes quickly, then you can pursue that option. You can learn more about catfacing and other common tomato deformities, along with what causes them, in my article here. However, it will not kill them directly. Now that we know when to protect tomato plants against cold and frost, it’s time to talk about how you can do it. Selvey studied interior design at the University of Arkansas. Row covers offer 3 to 5 degrees Fahrenheit of cold protection. A temperature below 40 degrees Fahrenheit will cause stunted growth, wilted leaves, and pitting of fruit. We’ll also look at ways to protect young tomato plants from spring frost and mature tomato plants from fall frost. At 32 degrees Fahrenheit or lower, frost occurs. Working backwards 42 days, we find: 9 days in May, 30 days in April, and 3 at the end of March, for 42 days total. You might be doing a great job when it comes to choosing tomato varieties and your planting schedule. In either situation, a cold frame will help. Ideal Range: The plant's preferred temperature range. At night, the temperatures have to be maintained at a lower level, ideally between 12-18 degrees Celsius. Now you know when to protect your tomato plants from cold, and how to do it. The result is below-freezing temperatures that generally kill all but the most cold-tolerant plants. Tomato plants tolerate temperatures that are less than 55 degrees and over 100 degrees Fahrenheit, but after a few days of extreme to low or high temperatures, the plant will experience blossom drop. Always remember to watch for frost in the weather forecast! If the plant is crowding the pot, repot it into a larger container before taking it indoors. You may be able to provide cold protection to help tomato plants survive a frost or freeze on a cold night (more on this later). Once you move your tomato plants to the greenhouse, keep the door and any vents closed at night to trap heat inside. In this case, row covers will help to keep your plants warm. Apr 30, 2019 Re: How cold does it need to be to kill tomato plants « Reply #9 on: May 01, 2019, 12:40 » My neighbour planted seed of various types some 3 weeks ago in an unheated g/h. Another option is to buy a pre-fabricated greenhouse. The answers are again environmental. When tomatoes do appear, you may see catfacing (a scarring injury of the fruit, thought to be caused by cold exposure). Sometimes just shaking the plants will do the trick. A temperature of 45 degrees Fahrenheit (7.2 degrees Celsius) may not cause severe, immediate damage to your tomato plants, especially if you protect them. Of course, my tomato plants would not do very well if the nighttime temperatures get into the 40s towards the end of the season. Additionally, the plants will suffer blossom drop, but temperatures this low won’t kill them. learn more about Siberian tomatoes on the Reimer Seeds website. Then, I work 77 days backwards from there: 3 days in October, 30 days in September, 31 days in August, and 13 days in July. Any colder, and you might want to wait (or use an extra cold protection measure, such as cloches). Farmer’s Almanac has a tool that you can use to find the dates for your region. Frost protection is especially important for tender plants such as tropical houseplants, succulents, begonias, impatiens, peppers, and tomatoes. Spring nighttime temperatures need to be 16.7 to18.3 degrees Celsius (62 to 65 degrees Fahrenheit). Of course, there are some ways to protect your tomato plants from the cold, both at the start and the end of the growing season. learn more about hardening off seedlings in my article here. According to the Colorado State University, frost will kill most warm-weather plants, including tomatoes. When it comes to cold, the temperature and duration of the cold will determine how tomatoes are affected. In this article, we’ll talk about how much cold tomato plants can tolerate, and how they are affected at different temperatures. Row covers are great because they can protect your plants from pests at the same time that they protect from cold. The only drawback of using a cloche in the garden is that your tomato plant will soon outgrow it. Before putting transplants in the greenhouse, monitor the temperature with a thermometer. The goal here is to briefly expose them to cooler temperatures than they would like (not freezing or damaging temperatures!). If you want to read some of my most popular posts, check out the “Best of GreenUpSide” page here. learn more about Tiny Tim tomatoes on the Victory Seeds website. If you are experiencing a particularly cool or scorching hot summer the natural ripening process can be severely impacted or even halted if the temperatures stray from ideal for extended periods of time. The fruit of warm season crops like tomato and pepper can be injured by low temperatures. Also, you may see catfacing (a scarring deformity) of fruit that forms later in the season. As the plant tries to recover, you will see whether all the leaves are frost-damaged or whether some have been left unharmed. learn more about Polar Baby tomatoes on the Reimer Seeds website. ~Jonathon. That being said, if the temperature gets lower than 40 degrees Fahrenheit, there will be trouble for your plant. In the short term, cold temperatures will slow the growth of a tomato plant. For example, let’s say I want to grow Fourth of July tomatoes, which mature in 49 days. At 40 degrees Fahrenheit or lower, tomato plants will sustain chilling injury after prolonged exposure. Watch the weather forecast often. learn more about Polar Star tomatoes on the Reimer Seeds website. You have two choices to bypass this limitation: For the second option, the question is: when should you start the seeds? However, if the weather does not cooperate, a frost in late spring or early fall can damage your plants or fruit. Researchers found that chilling tomatoes at temperatures below 12 degrees Celsius, or 53.6 degrees Fahrenheit, hampers the enzymes in the fruit. If it calls for a hot, sunny day, then leave the greenhouse door open before you leave the house. This hole will let your plants breathe on a hot day by allowing extra heat to escape. Cool soil stunts plant growth and prevents root development. Then, cut out the bottom of each container, and put one container over each plant. Sometimes, your tomato plants are too tall for cloches, but they will still need cold protection. Technically tomatoes will survive with temperatures as low as 33° F (0.5° Celsius). A little research will reveal some cold-tolerant tomato varieties that can thrive in your region – even when cold threatens. Growing Temperatures for Tomatoes Tomatoes can tolerate a night time temperature falling to 13.5ºC but if the daytime temperature falls below 15ºC for a week … You can also use cold treatment to toughen up your tomato plants before transplant. At that temperature, you could expect nearly every seed to germinate. © Copyright 2020 Hearst Communications, Inc. In fact, you can transplant tomato plants outdoors in May where I live. At What Temperature Should You Cover Tomato Plants? Just be sure to take them off if it gets too warm – this will help to keep your tomato plants from overheating. The table below summarizes the temperatures that will negatively impact tomato plants and the effects you might see. According to the University of Illinois Extension, the texture and flavor of the fruit will decline at these temperatures. According to Penn State University, flowers may also drop off of the tomato plant. The major condition is where you live. It also makes the plant stronger and more resistant to cold at the other end of the season, when fall frost threatens. Protect strawberry plants when freezing weather hits in spring by beginning to sprinkle them just before their temperature drops to 32 F. Ice will form on the plants; if you keep the ice wet, the plants' temperature will stay at 32 F. The task requires applying 1/10 to 1/15 inch of water per hour with the sprinklers rotating once each minute. Otherwise, tomato growing season might end before it really begins! You can also see my illustration of ideal temperature ranges for tomato plants here. Three nights that week with temperatures below 40 degrees F can set back newly planted plants. First, look at the time to maturity for your plants (you can find it on the seed packet or on the website where you bought the seeds from). Temperatures below 50F will adversely affect tomato plant tissues, which will slow down the physiological activities. In other cases, your spouse yells at you for keeping too many plants indoors. I hope you found this article helpful. Night Temperature For Tomatoes If temperatures threaten to get much colder than 27 degrees Fahrenheit, it might be time to harvest your tomatoes and let them ripen indoors. A lower zone number means that it will be more difficult to grow tomatoes that need a long season. Houseplants need to be taken indoors before overnight temperatures dip below 45 degrees Fahrenheit. According to the University of Idaho Extension, they are good for protecting against short burst of frost, but not a prolonged freeze. If these same broccoli plants had experienced cool weather, they would probably survive the sudden cold. But when spring comes, we are eager to get our gardens planted, and we don't want to wait around until midsummer to plant beans. Does your lettuce need to be protected from frost? Lower temperatures will prevent the tomato plant … First things first – that means choosing the best tomato varieties for your particular climate. At 50 degrees Fahrenheit or lower, flowering tomato plants will produce less pollen, decreasing fruit set and yield.