FIMBY: To pick or not to pick those tomatoes?

This is another in our Food in My Back Yard series, devoted to edible gardening.

August heat can disrupt Sacramento’s favorite crop: tomatoes. Too much heat and plants not only refuse to set more fruit, the tomatoes hanging on the vines refuse to turn red.

You may be better off picking those not-quite-ripe toms and letting them reach full color indoors. That’s especially true if temperatures are forecast in the upper 90s or higher (as in later this week).

Leaving tomatoes on the vine until they reach maximum ripeness is a source of home-grown pride. (Tomatoes won’t get any sweeter or flavorful once picked.) But that comes with risks:

* Bugs or other pests love ripening tomatoes, too. Pick those big toms before pests start nibbling.

* Exposure to too much heat can cause the fruit to turn mushy before it turns red.

According to university research, a couple of factors impede ripening.

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 impacted, too. (This is a problem in container-grown tomatoes.) It’s also a reason not to use black mulch or rocks around tomatoes; the mulch or rocks absorb too much heat.

Also impeding ripe tomato production: Too much shade or too much fertilizer.

Tomatoes need at least six hours of sun daily to produce consistent fruit. (Is that under-performing tomato plant now getting a lot of shade from nearby trees, sunflowers or other tomato cages?) However, some shade in the late afternoon when our sun is at its hottest is a good thing – it prevents sunburning the fruit.

Too much nitrogen fertilizer leads to vines with lots of lush leaves – but no tomatoes. From here on out, feed tomatoes a little bone meal or other phosphate-rich fertilizer to prompt fruit production – but no more nitrogen.

Lack of fruit or ripeness could also be up to tomato variety. Heirloom varieties tend to be extra fussy. Brandywine is notorious for its lack of production in Sacramento. They need just-right conditions in order to produce a good (or any) crop.

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,” said 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.”