It only affects individual fruit, not the whole plant.
It’s caused by a lack of calcium uptake in the plant, and it’s pretty well universally agreed among experienced tomato growers that stressed plants find it hard to take up and metabolise calcium properly, even if it is available to the plant.
Usual advice is that consistency in watering is the most important way to prevent the problem … some folk find using a feed high in calcium can be helpful … others find it makes no difference.
Of course, this year in particular there are other stresses on our plants … the high temperatures in particular. Not much we can do about them (in the short term at least). 🙄
Its worth bearing in mind, particularly with a cooking type tomato such as San Marzano, that if you cut away the affected part of the fruit the rest can be used for sauces etc.
Hope that helps.
Gardening in Central Norfolk on improved gritty moraine over chalk ... free-draining.
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San Marzano does seem particularly prone to it
https://forum.gardenersworld.com/discussion/comment/751559#Comment_751559
Gardening in Central Norfolk on improved gritty moraine over chalk ... free-draining.
Its worth bearing in mind, particularly with a cooking type tomato such as San Marzano, that if you cut away the affected part of the fruit the rest can be used for sauces etc.
Hope that helps.
Gardening in Central Norfolk on improved gritty moraine over chalk ... free-draining.