Tomato seedlings suffer cold damage in temperatures below 60 degrees Fahrenheit. Some tomato varieties are bred to be more cold-tolerant and can set fruit when it's below 55 degrees Fahrenheit.
Scientists in the ARS Photosynthesis Research Unit at Urbana, Illinois, have discovered a drop in the overnight temperature below 50°F can create a biochemical version of mission impossible for some crops like tomatoes, soybeans, and corn.
Plants need to be transitioned indoors before the outside temperature starts dropping below 45 degrees Fahrenheit (7 degrees Celsius) at night.
It's sunny again… wait… ), but some vegetables won't be happy (and grow into incredibly prolific tomato producers - yes, I'm talking to you, tomato fanatics) if you don't protect them until night temperatures warm up consistently to 50 degrees and above.
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.
Fabric is a better choice because it will let moisture out while holding onto some heat from the earth. You could also cover the plants with buckets or storage totes and place hot water bottles near them. Also, my sympathies for the late frost.
When the tomato plants are about 10 to 12 inches tall and the last chance of frost has passed in your growing zone, it's time to plant the tomato seedlings in the garden or patio container.
Most houseplants are native to tropical areas and will not tolerate freezing temperatures. Many indoor plants will see damage when temperatures drop to the mid to lower 40s°F and nearly all will die if exposed to below freezing temperatures.
Depending on where you live, you might want to expose your tomatoes to morning sunlight, to afternoon sunlight, or to a combination of the two. Morning sunlight provides high-intensity light without excessive heat, therefore you should consider morning exposure if you live in a region with a hot climate.
Tomato Plants and Temperature
Tomato temperature tolerance for extreme heat or cold snaps is of extreme importance to the development of blossoms and subsequent fruit set. Blossom drop will occur in the spring if daytime temperatures are warm but night temps drop below 55 F. (13 C.).
Plan to bring in your houseplants when temperatures are forecast below 45 degrees F to protect them from stress and cold damage. Tender perennial herbs like Rosemary or Lemon Verbena can be brought indoors as well for winter cooking.
So will peppers survive 40 degrees? To sum it up, most peppers won't necessarily DIE from 40˚ F temperatures, but their growth can be stunted, and they may be slow to recover so it's best to keep them warm if possible.
Each plant has a different threshold when it comes to dealing with the cold. Some plants can survive outside even when temperatures hit freezing. Others need to be brought indoors when temperatures reach the mid-40s.
When to Bring Tomatoes Back Inside. Potted tomatoes that have been moved outdoors should be moved back inside before nighttime temperatures fall below 50 degrees Fahrenheit. Tomato plants crave warmth and do not react well to cold temperatures.
Even prolonged exposure to temperatures below 55 degrees F. (13 C.) can cause decay, pitting, and water-soaked areas on fruit. Sudden cold snaps can cause cucumber plant damage on leaves, stems, and fruit or even kill the plants.
So it may well be that you have to water your tomato plants several times a day or just once or twice a week. The only thing that really helps here is to observe carefully. Basically, however, only water when your tomatoes really need it. The roots also need air, so drowning them in water won't help.
Tomatoes thrive in loamy soils with good drainage and high organic matter content. Adding composted coffee grounds to planting beds is a great way to build healthy soil for tomato planting but won't provide all the required nutrients.
Tomatoes need eight hours of daylight to flower. Sunlight gives your tomato plants the energy to produce fruit, so if your plant doesn't have enough sunlight, you're less likely to see tomatoes fruiting.
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. Freeze – A freeze is when the air temperature is 32°F or below.
Marigolds can handle a bit of a chill, but they draw the line at frost. They can survive down to about 40°F, but it's not a party they enjoy. To prepare for cooler nights, especially in the unpredictable shoulder seasons of spring and fall, think like a marigold.
WHEN TO BRING PLANTS INSIDE. As a general rule, tender plants should be brought in when nighttime temperatures are below 50 to 55 degrees F, even if they are hardy for your zone. A plant's roots are more exposed when planted in a container versus in the ground.
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. Gardeners can use a frost date calendar to note their region's average dates of last frost in spring and first frost in fall.
In general, determinate tomatoes tend to do better in pots, so look for those. It's also possible to grow indeterminate tomatoes in containers, of course, as long as you provide enough support and soil volume.
Soil in containers warms up and dries out more quickly than in the ground. During hot weather, plants may need watering once or twice a day. The goal is to keep containers consistently moist but not soggy. Too little water will stress plants, leading to stunted growth and a reduced harvest.