Maintaining temperature in the ideal range is very important for tomato fruit set. The optimum temperatures are 60-75°F (night) and 60-90°F (day). Studies showed that exposing plants to 3-h periods of temperatures above 104°F on two successive days may caused fruit set failure. Not only is the maximaltemperature critical for fruit set, maintaining night temperature in the ideal range is also essential. Effects of high temperature on fruit set are primarily on the stage of pollen development, which occurs about nine days before flowers open. High temperatures also affects flower structure by causing stigma exertion that prevents pollen from successfully landing on the stigma (Figure 1). After pollination, pollen germination can be severely reduced at temperatures above 100°F.
Preventing temperatures from reaching the extremely high level is important in high tunnel tomato production. Since biomass production and flower numbers are less likely to be affected by high temperatures compared to fruit set, maintaining ideal temperature could be overlooked until it is too late. As the temperatures continue rising in the season, it is critical for high tunnel growers to timely vent their high tunnels to prevent temperatures reaching extremely high levels.
Figure 1. Note stigma of tomato flower on the left was more extended compared to flower on the right. In addition to temperatures, genetic factors, nutritional status and light might cause stigma exertion.
FAQs
Tomato plants can tolerate extreme temperatures for short periods, but several days or nights with temperatures above 90oF (daytime) or 72oF (nighttime) will cause the plant to abort flowers and fruit (Fig.
What temperature is too hot for tomatoes to set fruit? ›
When high heat lingers with days above 100°F and nights over 80°F, most tomato ripening stops altogether. Fruit left on plants may have some color on the outside, but may still be green inside.
What is the effect of high temperature on tomatoes? ›
Tomato plants drop flowers when exposed to several days of daytime temperature above 29 °C and nighttime temperature above 21 °C, while reproduction is severely affected at day temperatures above 35 °C [10]. Flower drop can occur within just four hours of tomato exposure to daytime temperature above 40 °C [8].
What temperature damages tomatoes? ›
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.
What does heat stress look like in tomatoes? ›
For a tomato plant, when sufficient water is available in soil, visual symptoms of heat stress include reduced plant size, low number of leaves, small and curling leaves, and dry flowers.
Is 100 degrees too hot for tomato plants? ›
Adequate water will help reduce the severity of heat stress, but tomato plants, like many of us, will be happiest with temperatures below 90 degrees. If your tomato plants aren't developing fruit, blame the heat. Night temperatures above 75 degrees and day temperatures above 95 degrees can cause poor fruit onset.
How to increase fruit set in tomatoes? ›
The use of growth regulators such as auxins at anthesis can stimulate fruit set, and increase fruit size especially under low light and low temperature conditions.
What happens to tomatoes below 50 degrees? ›
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.
What temperature causes blossom drop in tomatoes? ›
Temperatures over 104̊o F/40o C for only four hours can cause the flowers to abort. If the night temps fall below 55 o F or rise above 75 o F or if the day temps are above 85o F, the pollen becomes tacky and nonviable. Pollination cannot occur. If the bloom isn't pollinated, the bloom dies and falls off.
Does heat destroy nutrients in tomatoes? ›
So what's a tomato-lover to do? In one study, researchers at Cornell University heated tomatoes and found their vitamin C content decreased as cooking time increased. Tomatoes cooked for 2 minutes had 10% less vitamin C than an uncooked tomato, and those cooked for 30 minutes had 29% less vitamin C.
Young plants are all about that vegetative life, so a cooler 66°F (19°C) average nudges them towards fruit production. As they mature, a slight uptick to 68 to 72°F (20 to 22°C) during the day and 62 to 66°F (17 to 19°C) at night helps maintain a balance of leafy and fruity growth.
What causes tomatoes to cat face? ›
The disorder occurs when weather conditions interfere with proper pollination and fruit development. Cold weather (below 50°F) and hot weather (above 85°F) can both cause catfacing. Dramatic fluctuations in soil moisture can also cause tomatoes to develop cracks in the stem end of the fruit.
Do I need to cover my tomatoes at 40 degrees? ›
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.
How often should I water tomatoes in 100 degree weather? ›
Tomatoes growing in pots have high water needs. The relatively small soil volume in the container limits the amount of water available to plants. During the heat of summer, container-grown tomatoes often need to be watered daily. Hot, windy conditions might require twice daily watering.
What are the first signs of heat stress? ›
Symptoms
- Cool, moist skin with goose bumps when in the heat.
- Heavy sweating.
- Faintness.
- Dizziness.
- Fatigue.
- Weak, rapid pulse.
- Low blood pressure upon standing.
- Muscle cramps.
What Sunscald Looks Like. Sunscald can affect the leaves as well as the fruit. “Leaves with white or brown spots, and tomatoes with cracks or patches of blotchy white, yellow, or gray spots are all indications of sunscald,” says McDonald.
Is 90 degrees too hot for tomatoes? ›
In temperatures of 85 to 90 degrees or so and nights above 75 degrees or so, your tomato plant may go into survival mode until temperatures come back down. Plants may fail to produce pollen or fail to pollinate and the blossoms will simply drop off until the temperatures come back down.
Can it be too hot for tomatoes to ripen? ›
At the same time, tomatoes do not produce lycopene and carotene, the pigments responsible for ripe tomato color, when temperatures are above 85 deg. F. So, extended periods of extreme heat cause tomatoes to stop ripening.
What nighttime temperatures can tomatoes tolerate? ›
Don't Expose Young Plants to Cold
The damage won't be noticeable right away but the plants will experience stunted growth, poor flowering and fruit set, and catfacing. Wait to plant the tomatoes until nighttime temperatures remain consistently above 60 degrees Fahrenheit.
What temperature do you harden tomatoes? ›
Let's use tomatoes as an example: The guide states they can be planted April 5–July 30, so two weeks before April 5 if the temperatures are at least 45-50 degrees during the day, move plants outdoors to a shady, protected spot, for no more than 2-3 hours.
