What causes tomato end rot?
I live in Vaughan. Zone 5 or 6.


Blossom end rot relates to the lack of calcium brought to the plant from the soil. It can affect peppers as well but is most common in tomatoes. It is commonly believed and widely published in horticultural research that the reason is not that the soil lacks calcium, but rather, inconsistent moisture causes it not to be brought into the plant. Usually this is because the soil is allowed to dry out completely. Although we have had a lot of rain this summer in the form of intense storms, we have also experienced very high temperatures so that the soil dries quickly.

However, recently the Ontario Ministry of Food and Agriculture has suggested that there are other causes, including very high temperatures and intense sun, which has certainly also been the case this summer.

The good news is that you can pick off those first tomatoes that have been affected and by keeping the soil consistently moist (not soaked) from now on, it is likely that any new tomatoes that form and ripen should be fine.

For a detailed technical discussion of blossom end rot, you might like to visit the University of Rhode Island website here and the OMAFRA discussion paper here.