Sacramento Digs Gardening logo
Sacramento Digs Gardening Article
Your resource for Sacramento-area gardening news, tips and events

Articles Recipe Index Keyword Index Calendar Twitter Facebook Instagram About Us Contact Us

Tomatoes won't ripen? Could be too much sun, heat

Triple-digit temperatures can keep tomatoes from turning full red, says Farmer Fred

Jetsetter tomato seems stuck on orange instead of turning full red. Blame the heat.

Jetsetter tomato seems stuck on orange instead of turning full red. Blame the heat.

Debbie Arrington

It seems counterintuitive; instead of ripening faster as days get hotter, tomatoes seem to slow down.

A lot of Sacramento-area gardeners are experiencing that phenomenon firsthand as they watch their tomatoes very very very slowly change from pinkish to full red.

Farmer Fred Hoffman, lifetime master gardener and award-winning radio host/podcaster, made that point in his weekly newsletter and “Garden Basics” podcast.

“Many area gardeners are wondering about the lack of color of their tomatoes now, in late summer,” Hoffman said. “Blame the triple-digit heat spikes that have occurred coast to coast for the slowdown this summer.”

According to university research, a couple of factors are in play. In late summer, tomato vines may have fewer leaves. Less foliage means less photosynthesis, which means less energy and slower growth for the plant. Without that boost of energy, its green tomatoes take longer to grow to size and ripen.

In addition, red pigments can’t form properly in triple-digit heat. Yellow and orange pigments seem to do OK, which leads to ripe tomatoes with splotches. They’re fine to eat, although not classically perfect.

Another factor: Soil temperature. If tomato roots stay over 80 degrees, fruit ripening is affected, too. (This is a problem in container-grown tomatoes.)

If your tomatoes seem to be taking forever to ripen, the solution is easy: Pick them. Then let them ripen in a dark space indoors (such as in a box on the kitchen counter). Their flavor may not be as intense as if vine-ripened, but they’ll be red and juicy – and finally ready to eat.

“Light conditions have very little to do with ripening," report Cornell University researchers. “Tomatoes do not require light to ripen and in fact, fruit exposed to direct sunlight will heat to levels that inhibit pigment synthesis. If temperatures remain high outdoors, these picked fruit will ripen more quickly, perhaps by as much as five days.”

Hoffman also has great advice this week on worms (or to be more specific, caterpillars) that eat tomatoes, and how to tell the culprits apart.

Listen to Farmer Fred’s podcast and newsletter here:

Check out his "Get Growing" website here:


0 comments have been posted.

Taste Summer! E-cookbook


Find our summer recipes here!

Newsletter Subscription

Sacramento Digs Gardening to your inbox.

Local News

Ad for California Local

Thanks to our sponsor!

Summer Strong ad for

Dig In: Garden Checklist

For week of Oct. 1:

Make the most of this cooler weather. Get to work on your fall garden:

* October is the best month to plant trees, shrubs and perennials. Plants become established – sending down deep, strong roots – faster in warm soil.

* Divide and replant perennials. Add a little well-aged compost and bone meal to the planting hole, but hold off on other fertilizers until spring. Keep the transplants well-watered (but not wet) for the first month as they become settled.

* Now is the time to plant seeds for many flowers directly into the garden, including cornflower, nasturtium, nigella, poppy, portulaca, sweet pea and stock.

* Plant seeds for radishes, bok choy, mustard, spinach and peas.

* Plant garlic and onions.

* Set out cool-weather bedding plants, including calendula, pansy, snapdragon, primrose and viola.

* Reseed and feed the lawn. Work on bare spots.

* Dig up corms and tubers of gladioli, dahlias and tuberous begonias after the foliage dies. Clean and store in a cool, dry place.

* Treat azaleas, gardenias and camellias with chelated iron if leaves are yellowing between the veins.

* Clean up the summer vegetable garden and compost disease-free foliage.

* Harvest pumpkins and winter squash.

Taste Spring! E-cookbook


Find our spring recipes here!