You should only cover your tomatoes when temperatures get below 40 or 50 degrees Fahrenheit. Keeping the plants covered beyond those temperatures accumulates heat and can suffocate them and harm the mature tomatoes.
Temperatures between 38ºF and 55ºF won't kill tomato plants, but keeping them covered for an extended amount of time can. Remove coverings in the morning or once temperatures rise over 50ºF to give them extra light and warmth.
Tomato plants, in general, can survive temperatures down to 32°F for short periods of time. But sustained temperatures below 50°F can cause slowed growth, severe damage to foliage and fruit, and ultimately, death.
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 degrees.
So even though the weather forecaster isn't predicting a freeze, once temperatures start to drop below 40°F you need to be aware. Once temperatures drop below 40°F, you may want to start covering your plants with a frost blanket depending on what you're growing, which we'll get into in just a bit.
In general, a frost (31-33 degrees F.) will kill beans, cantaloupe, corn, cucumbers, eggplant, okra, peas, pepper, potatoes, sweet potatoes, squash, tomatoes, and watermelon. Colder temperatures (26-31 degrees F.)
To know when to cover your plants, you need to know when the plants you have are susceptible to frost damage. Some frost-tender plants need to be covered as soon as the temperature hits 32°F, while others can handle lower temperatures and/or longer freezing periods.
Nights with temperatures in the 40s won\'t kill your plants as impressively as frost, but those temperatures will stunt the growth of your tomato plants.
I like to take buckets and put them upside down over a plant. This works great for individual plants, like tomatoes and peppers. Push the top of the bucket down into the soil. That will make a nice seal, and keep more cold air out.
Second, know that a light frost—32°F and colder—kills all tender plants such as tomatoes. Hardier plants such as spinach and kale will survive until there's a hard freeze—28°F and colder. (We explain the frost tolerance level of different crops below.)
-The key is to have your plants covered during the hours when frost develops. This critical period is from late night to early morning, when moisture on the plants can freeze. A good rule of thumb is to cover plants by 8 p.m. the night before a forecasted frost and uncover them by 8 a.m. the next morning.
High daytime temperatures (above 85 degrees Fahrenheit) and low nighttime temperatures (below 55 degrees Fahrenheit) interfere with pollination, causing blossom drop. Optimal growing conditions for tomatoes are daytime temperatures of 70 to 85 degrees Fahrenheit.
When daytime temperatures are consistently below 60ºF. When cool temps below 60ºF are the norm, tomatoes stop ripening. Bring them indoors and allow them to finish ripening there. When a heavy frost is in the forecast.
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). Before laying down a frost cover, first create a tent-like structure by driving several stakes into the ground around your tomato plants.
Watering in the morning is ideal from a water efficiency standpoint (less evaporation/water loss), and it also gives the foliage plenty of time to dry out (not a problem if you're using drip irrigation). Overhead irrigation of tomato plants late in the evening or at night is a no-no.
Too much standing water and moisture on the plants themselves is going to create a host of problems. By watering early in the morning, you will create an efficient routine that works in tandem with the plant's natural biological functions. Avoid watering in the evening at all costs.
Cover them during the cold hours of night. During the day, the soil absorbs the heat from the sun. By covering plants in the evening, the covering captures the heat the the soil re-radiates out into the night.
The general advice is to give tomato plants as much sun as possible to produce the best fruits. However, in extreme heat, too much can turn out to be a bad thing. In hot climates where temperatures frequently hit above 85F, a full day of sunlight will be too intense for tomato plants.
If it stays cold for more than one night, can I keep my plants covered, or should I remove the coverings at some point? A. Our recommendation would be to remove the cold protection covering once temperatures are above 32 degrees.
Avoid watering when temperatures are below 40°F or when sustained freezing temperatures are expected within 24 hours as this water will freeze and not be available to the plants.
The cold can mix badly with water, so just make sure the night time watering happens when temperatures are warmer. Late Spring, Summer and early Fall / Autumn generally have warmer months and this tends to mean overnight temperatures are warmer too.
Tomatoes don't thrive well in low temperatures, and the fruit is vulnerable to diseases in cold seasons. You should cover your plants when temperatures get to 40 to 50 degrees to protect them. Tomatoes don't do well in the cold, so covering them when there is frost keeps them warm and ensures continued growth.