Blossom end rot is a common issue that affects tomatoes, as well as other fruits such as peppers and eggplants. It’s characterized by a dark, sunken area on the blossom end (bottom) of the fruit. This condition occurs due to a calcium deficiency in the fruit, which can be caused by various factors:

1. Calcium Deficiency in the Soil: Even if there’s sufficient calcium in the soil, factors such as fluctuations in soil moisture, pH levels, and the presence of other nutrients can affect the plant’s ability to absorb calcium.
2. Inconsistent Watering: Irregular watering, especially in container-grown tomatoes, can lead to blossom end rot. This is because calcium is taken up by the roots with water, so inconsistent watering can hinder calcium uptake.
3. Excessive Salts in Soil: High levels of salts in the soil can interfere with calcium absorption by the roots.
4. Rapid Growth: Fast growth of the plant, often due to sudden availability of nutrients, can outpace the plant’s ability to absorb calcium, leading to deficiencies.
5. Environmental Stress: Extreme temperatures, particularly high temperatures, can increase the rate of transpiration, which in turn affects calcium uptake.

To prevent blossom end rot, you can take several measures:

• Maintain Consistent Moisture: Water your tomato plants regularly and consistently. Mulching can help maintain soil moisture levels.
• Soil pH and Nutrient Levels: Test your soil pH and ensure it’s within the optimal range for tomatoes (around 6.0 to 6.8). Also, make sure your soil has adequate levels of other essential nutrients besides calcium.
• Calcium Supplementation: Some gardeners apply calcium supplements to the soil or spray calcium solutions directly onto the plant to prevent blossom end rot. However, this approach may not always be effective if other factors are causing the deficiency.
• Avoid Excessive Fertilization: While tomatoes require nutrients to grow, excessive fertilization can lead to imbalances that interfere with calcium uptake. Use fertilizers according to the plant’s needs and follow recommended application rates.
• Choose Resistant Varieties: Some tomato varieties are more resistant to blossom end rot than others. Choosing these varieties may help reduce the risk.

By addressing these factors and providing optimal growing conditions for your tomatoes, you can minimize the risk of blossom end rot and enjoy a healthier harvest.