It is nearly the end of August and we should be awash in tomatoes from the garden or the farmers market right now.
This time of year, we should have eaten every type of tomato dish we could think of by now. Every backyard picnic table should be unsuitable for picnicking right now because they should be covered edge to edge with red, yellow and purple tomatoes.
But this is not the case this growing season as tomatoes have been very slow to set fruit and ripen. And it’s not just backyard gardeners who are suffering from a shortage of tomatoes, as farmers who sell at area farmers markets are also reporting slow ripening of tomatoes and reduced yields.
There could be several reasons for slow ripening of tomatoes, but the primary culprit is likely the variable weather that we have experienced this growing season, specifically air temperatures.
Know your varieties
Every tomato variety has a specific number of days to maturity — when tomatoes are ripe and ready for picking. Larger-sized tomatoes tend be longer season varieties, while varieties with smaller fruit, such as cherry tomatoes, tend to ripen more quickly.
Most varieties ripen six to eight weeks after flowering and pollination. It is normal for most varieties that producer larger fruit to take longer to ripen. If you have forgotten the maturity dates for the varieties that you planted, check the seed packet, seed catalog or plant tag to determine when you can expect the majority of your tomatoes to ripen under typical circumstances.
Heat-loving to a point
Tomatoes are heat-loving plants, which is why we never want to get too excited about getting them transplanted out in the garden too early in the season. Especially in their young vegetative stage, tomatoes thrive on warm air temperatures and soil temperatures. When these plants begin to flower and set fruit, excessively hot air temperatures can cause flowers to drop before fruit begins to set, reducing the number of tomatoes produced and delaying harvest.
Mild temperatures required for ripening
Once tomatoes have grown to their mature fruit size and start to turn from dark green to a lighter green and cream color, the ideal air temperature range for ripening is 68 degrees to 77 degrees. When air temperatures rise above 85 degrees to 90 degrees, the ripening process slows significantly and can even stop. At these temperatures, lycopene and carotene, pigments responsible for giving tomatoes their typical orange- to red color cannot be produced. As a result, the fruit can stay in a mature green phase for a long period.
The days in June and July when the mercury in Columbus hit a high of 90 degrees or above may have delayed ripening of tomatoes this season. The cool evenings in July were not helpful to the ripening process either.
What’s a tomato grower to do?
While there isn’t much a gardener or farmer can do about the weather, there are some cultural practices which tomato growers can adjust to hasten ripening of tomatoes. If you have been providing regular fertilization since fruit began to set, reduce the rate of fertilization, particularly nitrogen fertilizer, as this causes the plant to produce additional foliage and slow the ripening process. Once tomatoes flower and set fruit, a fertilizer high in potassium should be applied.
If you haven’t pruned your tomatoes, consider removing some of the lower leaves and lateral branches so that the plant puts more energy into fruit production and ripening.
If your tomatoes have blight on the lower portion of the plants, remove yellowed, spotted, and moldy leaves so that the plant puts more energy into fruit development and ripening instead of fighting disease.
If all else fails, tomatoes can be brought indoors to complete the ripening process, but do not store them in the refrigerator, as cold temperatures will cause sugars to begin to turn to starch, making them tough.
Mike Hogan is an associate professor at Ohio State University and an educator at the OSU Extension.