Zippers On Tomatoes – Information About Tomato Fruit Zippering

Zippers On Green Tomato Plants
(Image credit: Mila Usmanova)

Arguably one of the most popular vegetables grown in our home gardens, tomatoes have their share of tomato fruit problems. Diseases, insects, nutritional deficiencies, or over abundance and weather woes can all afflict your prized tomato plant. Some problems are dire and some are cosmetic. Amongst this plethora of ills is tomato plant zippering. If you’ve never heard of zippers on tomatoes, I bet you’ve seen them. So what causes zippering on tomatoes?

What is Tomato Fruit Zippering?

Tomato fruit zippering is a physiological disorder that causes a characteristic thin, vertical scar running from the stem of the tomato. This scar may reach the entire length of the fruit to the blossom end. The dead giveaway that this is, indeed, tomato plant zippering, are the short transverse scars crisscrossing the vertical marring. This gives the appearance of having zippers on the tomatoes. The fruit may have several of these scars or just one. Zippering is similar, but not the same, to catfacing in tomatoes. Both are caused by pollination problems and lower temperature fluxes.

What Causes Zippering on Tomatoes?

Zippering on tomatoes is caused by a disorder that transpires during fruit set. The cause of zippering appears to be when the anthers stick to the side of the newly developing fruit, a pollination problem caused by high humidity. This tomato problem seems to be more prevalent when temperatures are cool. There is no option for controlling this tomato fruit zippering, save for growing varieties of tomatoes that are resistant to zippering. Some tomato varieties are more prone than others, with Beefsteak tomatoes being amongst the worse afflicted; presumably because they need higher temperatures to set fruit. Also, avoid excessive pruning, which apparently increases the odds for zippering, as can excessive nitrogen in the soil. Never fear though if your tomatoes are showing signs of zippering. First off, usually not all of the fruit is affected and, second of all, the scar is just a visual issue. The tomato won’t win any blue ribbons, but zippering does not affect the flavor of the fruit and is safe to eat.

Amy Grant

Amy Grant has been gardening for 30 years and writing for 15. A professional chef and caterer, Amy's area of expertise is culinary gardening.