Why This Overhyped Tomato Blossom Rot Solution Might Be A Waste

Blossom-end rot occurs when a tomato (Solanum lycopersicum) plant cannot deliver enough calcium to the fruit. It shows up on the end of the tomato opposite the stem, where the blossom was, in the form of splotches or bruises, usually on the first fruits of the season. It also affects peppers, vine crops like squash and cucumbers, and eggplant. Blossom rot isn't just unsightly — it reduces the quality and quantity of fruit. While it's true that tomatoes with blossom end rot have a calcium deficiency, spraying the foliage or the fruit with a calcium solution will not solve the problem. Attempting to cure tomato plants this way is a waste of both time and money.

It may seem logical that the problem can be solved by applying relief directly to the plant with a spray, but neither the plant nor the fruit are capable of absorbing the intended remedy. Tomato plants can suffer from blossom end rot even if the soil isn't calcium-deficient. The issue is not with how much calcium is available, it's with the plant's ability to take it from the soil and consistently deliver it to the developing fruit. Moisture is a critical element of this process, and inconsistent watering interferes with it. Calcium in the leaves can't move into the fruit, and sprays can't penetrate the fruit. Sprays simply can't cause the plant to take up the right amount of water from the soil or deliver it to the developing fruit. 

Commercial calcium sprays claim that the product prevents and corrects blossom end rot in tomatoes and other susceptible plants like melons, cucumbers, and peppers. Some cover their bases with the caveat that they are only a supplement to a regular fertilization schedule and may not provide all the nutrients the plant requires. Even with the disclaimer, calcium sprays don't address the real reason blossom end rot occurs in tomatoes, uniform soil moisture in the best type of soil for growing healthy fruits. Use the money you might have spent on a miracle cure like a foliar spray and spend it on an irrigation system for your plants and on mulch to regulate the water content of the soil. Tomatoes require about an inch of water a week. The easiest way to check if your plants need water is to stick your finger into the soil.

The proper soil pH also plays an important role in the amount of calcium available to the tomato plants, and calcium sprays can't fix this, either. Tomatoes require a pH between 6.0 and 7 to thrive. If the pH is too low, add lime at the rate of 3 to 5 pounds per 100 square feet. It's unlikely that the pH is too high, but if it is, you can lower it by adding a sulfur amendment. Other best practices for healthier tomato plants include amending your soil with compost and mulch. Some simple soil additions for tomatoes, like bone meal, can help the plants thrive.