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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: https://gardenbasics.substack.com/.

Check out his "Get Growing" website here: http://www.farmerfred.com/

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Garden Checklist for week of Nov. 3

November still offers good weather for fall planting:

* If you haven't already, it's time to clean up the remains of summer. Pull faded annuals and vegetables. Prune dead or broken branches from trees.

* Now is the best time to plant most trees and shrubs. This gives them plenty of time for root development before spring growth. They also benefit from fall and winter rains.

* Set out cool-weather annuals such as pansies and snapdragons.

* Lettuce, cabbage and broccoli also can be planted now.

* Plant garlic and onions.

* Keep planting bulbs to spread out your spring bloom. Some possible suggestions: daffodils, crocuses, hyacinths, tulips, anemones and scillas.

* This is also a good time to seed wildflowers and plant such spring bloomers as sweet pea, sweet alyssum and bachelor buttons.

* Rake and compost leaves, but dispose of any diseased plant material. For example, if peach and nectarine trees showed signs of leaf curl this year, clean up under trees and dispose of those leaves instead of composting.

* Save dry stalks and seedpods from poppies and coneflowers for fall bouquets and holiday decorating.

* For holiday blooms indoors, plant paperwhite narcissus bulbs now. Fill a shallow bowl or dish with 2 inches of rocks or pebbles. Place bulbs in the dish with the root end nestled in the rocks. Add water until it just touches the bottom of the bulbs. Place the dish in a sunny window. Add water as needed.

* Give your azaleas, gardenias and camellias a boost with chelated iron.

* For larger blooms, pinch off some camellia buds.

* Prune non-flowering trees and shrubs while dormant.

* To help prevent leaf curl, apply a copper fungicide spray to peach and nectarine trees after they lose their leaves this month. Leaf curl, which shows up in the spring, is caused by a fungus that winters as spores on the limbs and around the tree in fallen leaves. Sprays are most effective now.

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