"Everyone knows that calcium is essential for healthy bones and teeth. But you might not know that calcium is important for tomatoes, too! Tomatoes that are deficient in calcium develop something called 'blossom end rot', which cause tomatoes to rot at the 'other' end. Blossom end rot can be prevented and reversed by mixing little calcium into the soil around your tomato plants, either either by hand or with a tiller. Calcium helps in two ways. First, it builds up the cell walls and membranes. Also, because calcium is a base, it helps lower acidic soil. Your tomatoes will get the calcium by the water that it takes in through the roots. You should apply it at a rate of 3 - 5 pounds per 100 square feet. We have calcium in the form of Aragonite available in 25# and 50# bags."