Why Do My Tomatoes Go Black And Rotten On Their Tops?

Question

This years crop

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Answer 1

It doesn't look like rot to me. To me, it looks like a characteristic of that particular cultivar! Some tomatoes have striation such as this.

This guide will help you to grow tomatoes to their potential:

https://www.gardeningknowhow.com/edible/vegetables/tomato/growing-tomatoes-guide.htm