Tomato Sunscald: Why Too Much Sun Can Be Hazardous to Your Tomatoes’ Health

Tomato sunscald is a problem caused by growing conditions – specifically intense, direct sunlight for extended periods during very hot weather. The excessive sunlight discolors patches on ripening or green tomatoes.

What does tomato sunscald look like?

Photo: Colorado State University

Sunscald first appears as light patches on green or ripening fruit
Most often, sunscald develops on the side of the fruit that faces the sun
As the patches grow, they may blister and may become grayish-white
Affected sunscald tomatoes can develop black mold

When does sunscald affect plants?

When green or ripening tomatoes get too much direct sun, especially during very hot weather

How can you control sunscald?

Photo: Missouri Botanical Garden

Sunscald is irreversible once it’s impacted a tomato, but its progression can be slowed. You can leave exposed fruit on the vine and cover it with lightweight screen, shade cloth, or straw to protect if from further damage. You can also harvest sunscalded tomatoes and let them finish ripening on a windowsill or kitchen counter.

Can you eat tomatoes affected by sunscald?

Sure – as long as black mold hasn’t set in. To eat, simply slice off affected parts.

How can you prevent tomato sunscald?

Try some of these tips!

Choose heat-tolerant tomato varieties.
Don’t over-prune tomato plants, especially in hot climates. If you leave extra branches on plants, you’ll provide extra shade for fruit.
Cage tomato plants. Caging provides tomato support without requiring pruning, so foliage can provide shade to tomatoes, whereas traditional stakes and trellising expose fruit to maximum sunlight, which promotes sunscald. (Check out different tomato cages to find the right ones for you and your garden: stackable garden cages at Gardener’s Supply; the Ultimate Garden Cage at Garden.com; and Burpee’s popular XL Pro Tomato Cage.)
Keep plants healthy and treat tomato problems as soon as possible. Tomato wilts, blights, and leaf spot cause plants to drop foliage, which expose fruit to excess sunlight.
When the forecast is for extended hot, dry weather, shield plants with a lightweight screen, shade cloth, or straw to protect fruit from over-exposure and hopefully prevent sunscald.
Consider growing tomato plants upside-down to shade fruit.