Posted: 17/04/2014 at 07:38
Years ago Blossom End Rot was thought to be the result of soil deficient in calcium. Add calcium to the soil was the commonly suggested solution. These days, science has determined that BER is the result of the plant's inability to distribute calcium to the fruit via its internal mechanisms. The soil can be loaded with calcium, the plant just can't get it to the fruit in sufficient quantities.
Plant stress is thought to be the cause. Irregular watering is the most common explanation but strong winds, fluctuating temperatures, etc, can also be factors.
Then there's the fact that some varieties are more prone to BER than others. The plum varieties - San Marzano, etc - can be hit by it while other varieties, in the same bed, with identical growing conditions, escape it. It's happened to me. Very puzzling. There's obviously something in the plum variety genes that makes them susceptible.