Blossom end rot (BER) occurs when a plant cannot metabolize the calcium it needs to develop properly. This can occur when there is not enough calcium in the soil or when root damage and water stress reduce the uptake and movement of calcium through a plant. Occasionally, BER is the result of excessive nitrogen fertilization. It only takes a day for a lack of calcium to affect fruit, and that day can occur any time after blossom set.
Here are some tips on how to prevent blossom end rot on your vegetable crops:
1. Properly site and prepare your garden bed before planting. Most crops need full sun and loose, well-drained, organic soil.
2. Make sure soil pH is slightly acidic, between 6.2 to 6.8, for optimum nutrient uptake. Test your soil to see if calcium is recommended. You can use an Electronic Soil Tester to quickly measure fertility and pH or send a soil sample to your Cooperative Extension Service.
3. Avoid planting too early in cool soils as this can inhibit early root development, making the plant more susceptible to BER.
4. Start with a quality transplant: a healthy seedling with strong roots will make a healthy plant.
5. Avoid wide fluctuations in soil moisture by using mulch 2-3" deep. This will moderate the release of water to plant roots, and also keep the soil from drying out when it is directly exposed to the sun.
6. Avoid drought stress by making sure your plants get at least 2" of rain or water per week. Apply enough water to moisten more than the top inch of soil. Container grown crops will need more than 2" of -applied water per week in hot weather- check them daily if possible. Consider using drip irrigation or soaker hoses. One or two soakings are better than many light waterings.
7. Avoid over-fertilizing during the early fruiting stage, especially if the fertilizer contains high percentages of nitrogen. Use fertilizers specially formulated for tomatoes like Espoma Tomato-tone. These fertilizers have just the right amount of nitrogen and other micronutrients best for fruit production.
8. Avoid close cultivation around the base of plants when weeding. A layer of mulch should help prevent the possible disturbance or damage of fragile roots accidentally.
Unfortunately, once a fruit has BER it will not recover it is best just to remove it from the plant. The part of the fruit that it is not rotted is still fine to eat. The plant itself can still produce good fruit. BER most frequently occurs on fruit produced earlier and later in the season as this is when natural fluctuations in precipitation and cold weather occur.