Mastodawn

Forgotten Hero Jul 29, 2025

@buarth
It's called 'Blossom End Rot' (which sounds vaguely rude to me). I usually get a few on most plants.
Read all about it here:-
https://www.rhs.org.uk/problems/blossom-end-rot

Blossom end rot / RHS

Dark blotches on the ends of aubergine, tomato and pepper are alarming, but do not mean the end of the crop. This is called blossom end rot and is caused by lack of calcium in the fruits. By making minor adjustments in watering you will usually be able to protect subsequent fruits from blossom end rot.