Lincolnshire,
United Kingdom 
why does my tomatoes turn black on the underside when they start to ripen?
2 Aug, 2010
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« Scabious 'Butterfly Blue' purchased 6 weeks ago in 20cm pots (and not cheap!)...
Sounds like blossom end rot. Two things separately or a combination of both. Magnesium deficiency and irregular watering with drying out between being primary.
2 Aug, 2010