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.
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.
How Cold Can Tomatoes Tolerate? Tomato seeds won't germinate when the soil temperature is below 50 degrees Fahrenheit. 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.
People have asked, can peppers survive 40˚ F temperatures? Most peppers are not happy when temperatures drop below 50-60˚ F.
So when temperatures start dipping below 50º F, leave the tomatoes on the vine if warmer days and nights are forecast. But if temperatures have started on a steady downward slide, go ahead and pick the mature green tomatoes and bring them indoors.
However, warm-season vegetables such as peppers, tomatoes, cucumbers, melons and squash can be damaged if the temperature drops to 33 F. Consider these tips to help protect your plants as temperatures drop. * Cover plants at night.
Frost Hardy
Root crops develop more sugars when the soil temperature is below 40 degrees Fahrenheit; and Brussels sprouts are often best after a light freeze. Among the hardiest vegetables are cole crops, which can tolerate moderate freezes (24 to 28 degrees Fahrenheit) : Broccoli, cauliflower (26 degrees Fahrenheit)
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.
Daytime temperatures below 65°F can lead to fruit set failure—the pepper equivalent of stage fright. At night, anything under 50°F is an invitation to leaf curl and overall plant stress. It's like the plants are pulling their leaves up to their chins, trying to keep warm.
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.
Below 63°F, cucumbers do not grow. In such conditions, plants sit in the soil and become susceptible to damages caused by pests in the soil. With that said, check soil temperatures and be sure they are above 63°F before planting cucumbers.
Cover Plants
Once temperatures drop below about 28°F, covering is typically no longer effective at preventing cold damage. Occasionally even with covering you may still see damage at temperatures above 28°F, especially when the below freezing temperatures are prolonged (5 hours or more).
If you're looking for tips for protecting your plants from frost, avoid using garbage bags as plant covers. Trash bags are not the best protection against frost damage, primarily due to their material. Most garbage bags are made out of low-density polyethylene plastic.
Frost Advisory - This is when the temperature is expected to fall to 36 degrees to 32 degrees Fahrenheit. Freeze Warning - This is issued when there is at least an 80% chance that the temperature will hit 32 degrees Fahrenheit or lower. Light freeze - 29° to 32° Fahrenheit will kill tender plants.
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.
Tomatoes need to be kept well above freezing to survive. There's no point trying to put them outside – or even into a greenhouse – until your last expected frost date has safely passed. Temperatures below 10ºC (50ºF) can result in slow growth and problems with flowering and fruiting.
The hardiest ones aren't always the tastiest, but the varieties I have found to be very hardy are Cole and Mongolian Dwarf. (Both are great in cooler climates/short growing seasons and both are open-pollinated.)
Even if a chill doesn't kill them, it can dramatically slow down their growth. The best time to bring plants inside is when nighttime temperatures start to dip below 55 to 60 degrees F. (12-15 C.). Before bringing container plants indoors, check for pests that may be living in the soil.
At temperatures below 40°F, tomato plants will begin to wilt and brown from chilling injury. At best, the plant will experience stunting, wilting, and pitting of fruit.
Seedlings, with their tender new leaves, often give up the ghost when temperatures dip to 32-33°F. Tropical plants have differing low-temperature thresholds. Some keel over when temps fall to 40°F; others crumble at 35°F. Other plants are just hardy by nature and can withstand temperatures as low as 18-20°F.
Dry soil, temperatures above 90°F, or night temperatures below 60°F or above 70°F, can weaken plant growth. Transplant in late afternoon or on a cloudy, calm day. Pepper flavor is best when the season has been warm and sunny.
Harvest Guard® (also called row cover) is a lightweight fabric that can help warm the air and soil. If placed over a plant, leave enough fabric so the plant can continue to grow (it will push the fabric up as it grows), or use some sort of support to keep the fabric off the plant.
First, it's good to know which plants are sensitive to temps around 35 or 40 degrees F. These are common tender plants that will need some protection. Hanging baskets: begonias, calibrachoa, gerbera, impatiens, vinca, euphorbia, and scoparia.