Why does this tomato look so weird? Can I save seeds from it?
Thank you for contacting the Toronto Master Gardeners regarding your tomato oroblem.
From the photo it appears that your tomato is showing signs of what is known as zippering. This usually happens in high-humidity conditions when the anthers in the blossom stick to the sides of the newly developing fruit, and improper pollination occurs.This produces a scar as the fruit grows, extending from the blossom end to the stem. Sometimes an open hole develops in addition to the scar. See the Missouri Botanical Guide visual guide to Problems of Tomato Fruit. Large beefsteak tomatoes are among the worst affected.
The only option to controlling this disorder is to grow varieties not prone to zippering. For more information see the article by the Fairfax Master Gardeners titled 5 Tomato Problems
July 30, 2021