FIMBY: How to prolong fall tomato harvest

This is another installment in our Food in My Back Yard series, focused on edible gardening.

Happy fall! We’re officially in a new season and surveying the remains of our summer garden.

Several tomato vines still have green fruit; a few even have flowers. Does that mean fresh tomatoes for Halloween – or even Thanksgiving or Christmas?

Like all gardening, it depends on the weather. Tomatoes need warm days and warm nights to ripen on the vine.

Right now, we have both, with the first week of fall feeling like an extension of summer. And some heat is likely to stick around; the National Weather Service predicts Sacramento to stay at least in the 80s well into October with overnight lows in the upper 50s.

According to the Old Farmer’s Almanac, Sacramento’s long-range forecast is 5 degrees above normal through October and November. That means tomato vines and other summer crops will likely try to hang on longer than usual.

As it gets colder, tomatoes tend to go into slow motion. Ripening takes longer. Varieties that normally take six to eight weeks to fully mature may still be green three months from now (which would be pushing Christmas).

In theory, tomato vines could last until next year – just not outdoors in Sacramento. Tomatoes are a tender perennial; we just treat them like annuals. A native of the tropics, tomatoes are extremely sensitive to cold. They basically shut down fruit production in temperatures under 55 degrees. Frost will finish them off.

When it comes time to finally pull the vines, nighttime temperatures are often the deciding factor (along with lack of space for planting fall crops). When nighttime temperatures steadily drop to 50 degrees or lower, it’s time to say goodbye to those summer vines.

What’s the ideal temperature for tomato ripening? According to research at San Diego State University, the sweet spot for tomatoes are temperatures between 68 and 77 degrees. That’s not the afternoon high but the actual air temperature during day or night. Above 85 degrees or below 55, tomato ripening may be negatively impacted.

Research also shows that tomatoes – once they reach their full size and firmness – don’t need sunlight to turn red. They develop more sugar (and sweeter flavor) if allowed to ripen on the vine. But as for color, they’ll turn red on the kitchen counter or tucked inside a paper bag.

Midwesterners recommend pulling the whole vine, roots and all, with tomatoes still attached, then hanging the vine upside down indoors (in a barn, shed or garage) and allowing the tomatoes to ripen on the drying plant. They’ll continue to mature for weeks and can be picked as needed.

That method takes room; the kitchen counter works, too.

When nighttime temperatures start turning chilly, pick the full-sized but still green tomatoes and let them ripen indoors. Line a baking sheet or large pan with newsprint and let the tomatoes sit at room temperature, out of direct sunlight or heat.

Be patient. Tomatoes ripen more slowly on the counter than on the vine. But they do ripen (and still taste better than store bought).

And yes, you can have fresh tomatoes for the holidays!

Want them to ripen faster? Put tomatoes in a brown paper bag with an apple or banana. The fruit releases ethylene to speed ripening. The tomatoes will be red in just a few days.