Cutting back on watering tomatoes is just one trick to get the plants to ripen their fruit. There is no set amount to cut back, since everyone uses different quantities. Simply reduce the amount and/or frequency of your watering routine. Watch the plants carefully and don't let them wilt too much. The idea is to slightly stress the plants. Also, don't fertilize this time of year. Since it takes six weeks for tomato flowers to form fruits, pull off any flowers that have not already set fruit, and keep doing it the rest of the season (this should have been done mid- to late July, so you might want to pull off any tiny fruits at this point in time). You may also trim excess foliage, but be sure to leave enough on the plant to shade developing fruits to avoid sunscald. And if the weather starts to get really dicey, you can also root prune the plants by slicing the soil with a spade, about 10 inches to a foot away from the stem, in an incomplete circle around the plant i.e. maybe three slices. Do not remove the soil, just slice it. This will often result in ripening fruit within days.

The above is Technical Editor—Horticulture Cheryl Moore-Gough's response to a question from subscriber Lynn Bacon of Belgrade, Montana.