Heat Stress and Heat Stressed Tomatoes (Sanjun Gu) (2024)

FAQs

What are the symptoms of heat stress in tomatoes? ›

Leaf rolling and cupping

Corn and tomatoes are among many plants that commonly roll their leaves or cup in response to heat. Leaf surface area is minimized, and stomata (microscopic openings in leaves, like pores, that allow movement of moisture and gasses) close. Together, these reduce moisture loss in the plant.

When temps consistently hit the 95-degree range, tomatoes tend to stop producing red pigments, which means typically red fruits may instead ripen to orange. When high heat lingers with days above 100°F and nights over 80°F, most tomato ripening stops altogether.

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.

Heat stress includes a series of conditions where the body is under stress from overheating. Heat-related illnesses include heat cramps, heat exhaustion, heat rash, or heat stroke, each with its own symptoms and treatments. Symptoms can range from profuse sweating to dizziness, cessation of sweating, and collapse.

Scotts® TurfBuilder® UltraFeed™is an excellent choice for fertilizing lawns that tend to get stressed in the summer. It holds onto nutrients until your lawn needs them, then releases them. Because of this, a single feeding can last up to 6 months.

It can take anywhere from a couple of days to a couple of months for stressed plants to recover. Recovery time depends on the amount of damage that the heat caused to the plant. If a stressed plant is completely neglected during a heatwave, it can take several months or even be impossible to revive it.

It's not unusual for a tomato plant to appear vigorous and thriving one day and then be a limp collection of stems and leaves the next. Wilt is a sign of stress that needs to be addressed quickly to save the plant. Unfortunately, wilt is often not curable, but it can be prevented.

During the heat of summer, container-grown tomatoes often need to be watered daily. Hot, windy conditions might require twice daily watering.

How do you protect tomatoes in 100 degree heat? ›

Use shade cloth

Shade helps tomatoes during hot weather—of course it does. Go stand in the sun on a 100 degree day then move over into the shade, you don't get sunburned and feels cooler in the shade, doesn't it? Your tomato will think just like you and won't get sunscald/sunburn.

Tomatoes need plenty of sunlight to produce fruit, typically around six to eight hours a day. Too much sun and heat can cause tomatoes to get sunscald. “Sunscald happens when the tomatoes are hit with the direct waves of the sun without any protection, similar to sunburn on us humans,” says Key.

It's common for herbaceous (non-woody) plants that are suffering from heat stress to wilt during the heat of the day and then recover once the sun sets.

Other factors that affect fruit production in tomatoes during the hot, dry days of summer are water and plant nutrients. Avoid excessive nitrogen fertilization during the heat of summer.

Clothes pins or binder clips can be used to secure the row cover material or shade cloth and are easy to take off to allow access to harvest. Use of shade cloth can drop the ambient temperature by as much as 10 degrees and is often sufficient to keep tomatoes in that sweet spot of productivity.

One quick watering tip: Water deeply with a soaker hose if possible, but leave one side dry. Don't soak the plant all around because roots need to breathe. Here's the new growth and buds ready to bloom ten days later. Some of the lower leaves are still discolored, but I'll remove them as the new tops get stronger.

Leaf rolling or cupping

Plants will roll or cup leaves to reduce surface area and maintain the moisture in their leaves. Leaf rolling or cupping is a very common behavior in corn and tomato plants in response to heat stress.

The disease is highly contagious but not fatal. Its symptoms include rashes, high fever, body aches, joint swelling, fatigue, dehydration, discolouration of hands, feet, knees, buttocks, and other flu-like symptoms. If you notice any symptoms of tomato fever, immediately schedule an appointment with your doctor.

Sunscald results in a pale yellow to white spot on the side of the fruit facing the sun. This area may become a flattened, grayish-white spot. The surface may dry out to a paper-like texture. Sunscald spots are frequently invaded by decay-causing fungi and bacteria that further rot the fruit.