Are you planning to grow tomatoes in your vegetable garden? Excellent move. There is nothing more beautiful than watching how these small fruits grow larger by the day and slowly ripen. But to warn you, this culture is quite sensitive: unfortunately, tomatoes are sometimes victims of tip rot. Without warning, black spots can appear on the underside of some of them. Yes, it hurts your heart to see them rot prematurely. Certainly, it will be necessary to remove the weak spots, but it will not jeopardize the harvest. Follow our advice to prevent blossom end rot and harvest beautiful, healthy red tomatoes.

What causes blossom end rot in tomatoes?

You should already know that the cause of tip rot of tomatoes is not due to infection with insects or any other disease. In fact, this problem, better known as “black soil”, is mainly due to a lack of calcium caused by drought. However, tomato plants absolutely need calcium at all stages of their active growth, from roots to fruit. And this mineral is transported from place to place on the water.

Unfortunately, in a drought, when water is scarce, calcium cannot circulate freely, leading to this blossom end rot. If you’ve ever read up on this phenomenon, you’ve probably heard of home remedies that supposedly boost calcium levels, such as planting tomatoes with antacid tablets or sprinkling eggshells in holes. Granted, they’re not useless and won’t harm your plants, but they’re not miracles either and probably won’t make any real difference. In fact, it is mainly the lack of water that is the problem and prevents the calcium from reaching the fruit. Therefore, it is best to analyze the soil to determine if there is a deficiency of calcium or other vital nutrients.

Good to know: The first tomatoes of the season are the most sensitive and need more calcium for their growth. As the plant transports calcium from its roots, it is first consumed by the stems and leaves. So, there is not enough left for the ripening fruit. This can result in a black, mushy rot of the flower tip.

How to prevent and avoid the “black bottom” of tomatoes?

It must be understood that the “black soil” is the result of water stress, which greatly affects tomatoes. Either due to excess water or, conversely, due to drought. Fortunately, the good news is that this blossom end rot is not a real disease that will inevitably ruin your entire crop. Basically, it is not contagious: therefore, a tomato with symptoms will not infect its neighbors. It is not necessary to use chemical fungicides, as this will not solve anything. The only solution would be to achieve constant soil moisture. Are you looking for effective ways to prevent this nasty rot?  Here are 4 tips that you should follow carefully:

  1. Water tomato plants well

To make your tomatoes bloom and grow better, experienced gardeners recommend applying an average of 1 quart of water per day per tomato plant. Soaking hose or watering can is enough. This water supply is needed more when growing tomatoes in containers, where they dry out faster.


Tip: To prevent leaf diseases, avoid wetting the leaves when watering. Of course, you cannot prevent the rain from soaking the entire plant, but it can spread diseases. Ideally, the longer you keep the leaves dry, the better.

  1. Apply mulch around the tomato plants

An effective prevention solution? Spread a 5-inch layer of organic mulch around the base of your plants. It helps the soil retain more moisture to prevent rapid drying between waterings or rains. In addition, mulch also helps to smother weeds. Alternatively, straw, grass clippings, chopped leaves or shredded bark are also suitable.

  1. Do not overfertilize!

Beware: too much fertilizer can cause plants to grow faster without giving them time to properly circulate calcium for healthy growth. And remember that rapid growth can lead to blossom end rot. Finally, the best way to increase nutrients in the soil is to apply a layer of well-rotted compost (5 inches thick) to the soil before spring planting. Compost slowly releases nutrients while improving soil structure.

Note: Apply fertilizer only when recommended by a soil test and follow label instructions carefully.

  1. Take care of the roots

Learn that the roots are essential for calcium uptake, which prevents blossom end rot. Avoid disturbing the root zone of a tomato plant so it can absorb the maximum amount of calcium. For example, don’t dig into a plant’s root zone and keep weeds out with a layer of mulch.

Why are my tomatoes rotting from the bottom?

The causes of those dark spots on the bottom of tomatoes are usually due to a lack of calcium in the soil or poor root development. The latter is often due to improper watering (either too much water or, on the contrary, lack of water).

How to add calcium to tomatoes?

Calcium deficiency is a common problem in our orchards. To compensate for this deficit, you must first know how plants absorb calcium from the soil. The latter contains numerous minerals (insoluble for plants) such as silicates, carbonates or phosphates. To correct the calcium deficiency of your plants, there are several simple and inexpensive methods.

  • Eggshell

This technique is probably the most common: it consists in crushing an eggshell and burying it in the soil where you want to sow the plant. In this way, calcium is added to the soil, but in a minimal way, since it is added in a form that is difficult for the plants to dissolve. Ideally, if your soil has a slightly acidic pH, the peel will decompose better. Otherwise, it is also possible to macerate it in a mild acid, such as vinegar, to release more calcium.

  • Calcium oxide

If your soil is somewhat alkaline, it is already rich in mineral salts that contain calcium. However, if you are experiencing absorption problems, the calcium in the soil is probably not in a form that is soluble for your plants. In this case, it is better to add calcium oxide to the soil.

  • Milk

Another effective technique: since milk is full of calcium, you can take the opportunity to dilute a glass in 1 quart of water and spray it on the plant. It is also possible to spread powdered milk directly on the soil or on the leaves. A few grams every two weeks will be enough to provide the plants with sufficient calcium.