EasyBloom Forum

the first tomato to come of a heirloom tomato plant I bought to try out had a large rotten spot right on the bollom and my wife called it "blossom end rot". What is this and what do I do about it?

Hey Willie...you can tell your wife that she is correct. Blossom end rot is a disorder that is found often in solanaceous plants (in other words tomatoes, eggplants, peppers, etc.). Luckily, it is not caused from a bacterial or fungal infection. It's not because a worm decided to nest inside your tomato fruit. It is caused by a calcium deficiency in the plant when the fruit is developing. When I was in grad school, we had a visiting professor come into the lab who did some research that showed that a manganese deficiency exacerbates the problem and causes the calcium deficiency threshold to be higher than normal. Lucky for tomato growers, manganese is needed in such low quantities this is rarely a problem. In the following post I will tell you how to treat it.

Calcium deficiency in the plant can occur because of a number of things. First off, plain and simple, your soil may be deficient of calcium. Maybe a previous crop removed the calcium from the soil. There is a difference between calcium deficiency in the soil and in the plant. You can have a soil that is chock full of calcium, but the plant is still deficient in calcium. One reason why this could be is because of the soil pH. The soil should have a pH of around 6.5.

Another problem could be that the soil was inconsistently watered. In order for the plant to absorb and move that calcium from the soil, into the roots, up the stem and then into the fruit, a consistent supply of water is necessary. The calcium is dissolved in the water and moves up the stem in the water. If the soil gets very dry, the plant will stop moving water through the plant in an effort to keep from drying out and dying. As a result, the calcium also stops moving up the stem. Since tomatoes need LOTS of sun and a bit of warmth to make great tasting fruits, the soil that they are growing in can easily dry out. I would recommend using a mulch over the soil to decrease the rate of evaporation of water from the soil.

I would also fertilize using a balanced liquid fertilizer applied to the soil right as the fruit sets. (Fruit set can be defined by when the petals drop from the flower). This will provide calcium to the plant when it needs it most...when the fruit is developing. When using a fertilizer, I strongly suggest following the directions on the fertilizer's label. It is definitely possible to fertilize too much. I would also look for the source of nitrogen as primarily being nitrate and not ammonium.

Plants use calcium in a similar manner as animals do. The calcium in our bones make them strong. Plants use calcium in their cell walls, which provides them with added strength. You can see why a lack of calcium will cause the bottom of the tomato to be soft and gooey. It is also an easy way for pathogens to enter the plant. I would argue that the tomato that already has the blossom end rot is not salvageable, but if you follow what I recommended you may be able to prevent this disorder for the future fruits on your plant. I hope this is helpful. Please let me know if you have any further questions. Happy Gardening!!! Robby