Blossom End Rot: Why are My Tomatoes Rotting on the Vine?

Have you noticed a dry black or brown sunken spot of decay appearing on the blossom end of your tomatoes. This problem is common, especially on the first tomatoes of the season that you may have struggled to nurture after an extremely dry period. 

Tomatoes rotting on the vine is commonly caused by blossom end rot. It is a condition that results from low levels of calcium in the fruit. Blossom end rot is most common when the soil conditions are unfavorable for the absorption of calcium by the plant. 

Triggers include inconsistent soil moisture, root damage, excess soil salinity, and deficiency of calcium in the soil.

Why Are My  Tomatoes Rotting on the Vine?

Tomatoes rotting on the vine mainly result from blossom end rot. This disorder appears initially as a water-soaked spot at the blossom end of the tomato fruit. The affected tissues break down rapidly within a short period of time to become dry, sunken, black or dark brown and a leathery spot. 

This condition can affect tomato fruits at any stage as they mature. The first tomatoes of the season are likely to be affected. Other than tomatoes, blossom end rot can also affect other plants in the nightshade family including peppers or eggplants.

Blossom end rot results from insufficient amounts of calcium in the fruit. Inadequate amounts of this mineral in the plant tissues result from poor absorption or a deficiency in the soil. In some cases, it can be absorbed through the roots but settles in one part of the plant. 

Tomato plants grow rapidly, and it requires a steady supply of calcium and other minerals. However, several factors can limit the ability of tomato plants to absorb enough calcium. They include:

1. Inconsistent Soil Moisture Content

Blossom end rot is common when there is heavy rainfall that is followed by an extended period of dry weather, or it can happen if you are not watering your plants correctly. Calcium is transported within the plant only when there isan ample supply of moisture. 

When the plant is not receiving enough water, the fruits may continue to grow but will suffer from blossom end rot.

2. Damage to the Plant Roots

Any condition that reduces the ability of roots to absorb calcium predisposes tomato plants to blossom end rot. Some of the conditions that may damage the roots include nematodes, root-rotting fungal infections, under-watering, over-fertilizing, pests, root pruning or poor aeration.

3. Rapid Early Growth of the Plant

Rapid early growth also predisposes the plant to blossom end rot. The new growth draws heavily on the available calcium in the soil to the point of depletion. The plant may also not be able to absorb sufficient amounts of calcium quickly enough to satisfy the demand. 

4. Insufficient amount of Calcium in the Soil

Blossom end rot in tomatoes is a major sign of calcium deficiency. Plants require calcium and other minerals from the soil to grow rapidly and produce quality fruits. Always conduct soil tests to determine Calcium deficiency and take appropriate measures to correct it.

5. Excess Nitrogen in the Soil

Too much nitrogen in the soil may also cause blossom end rot in tomatoes. It promotes vigorous growth of foliage that depletes the available calcium in the soil before the fruit develops fully. The absorption of calcium also reduces when nitrogen is applied in ammonium form. The ammonium ions compete with calcium ions for absorption by the roots. 

6. Increased Soil Salinity

Increased salinity decreases the amount of calcium absorbed by the plant. Xylem, which is a transportation system of the plant, is also restricted by increased salinity. It prevents the fruits from transporting calcium to the blossom end. 

How do I Fix Blossom End Rot in My Tomatoes?

Blossom end rot can be controlled as follows:

1. Choose a Resistant Tomato Variety

When intending to plant tomatoes, choose a variety that is resistant to various problems, such as blossom end rot. Some tomato varieties are more prone to blossom end rot. Examples include Better Boy, Orange Banana and San Marzano. 

On the other hand, Blue Beauty, Black Cherry, Amish Paste, Opalka, Arkansas Traveler, Glacier, Stupic,e and Mortgage Lifter are among those that are less affected by blossom end rot.

2. Balance your Soil Moisture

Water your tomato plants deeply and evenly to prevent blossom end rot. Tomato plants require 1 to 2 inches of water per week depending on weather conditions. Watering deeply once or twice a week is better than daily light and frequent watering.

Be sure not to overwater your tomatoes. Overwatering can be detrimental just like inconsistent watering. Tomatoes in a water-logged area are likely to suffer from root rot, hence increasing the chances of blossom end rot. Drainage holes are non-negotiable when growing tomatoes in containers.

3. Improve Calcium Levels in the Soil

So, how do you improve calcium levels in the soil? Eggshells are actually the answer. Instead of tossing those eggshells into the garbage bin, you can use them to improve the calcium levels of your garden. Eggshells are rich in calcium, making them beneficial to tomatoes.

Crush the eggshells using a mortar and a pestle to form a smooth powder. Mix the powder with water and apply it at the base of your plants. 

Other materials that are rich in calcium include bone meal, oyster shell or gypsum. They release small and steady amounts of calcium into the soil as they decompose. 

4. Apply Foliar Liquid Calcium 5%.

Adding 1 to 2 tablespoons of liquid calcium 5% into a gallon of water and spraying your plants can help to prevent its deficiency. The mixture can be combined with other natural surfactants to increase adhesion. This treatment is supposed to stay on the leaves for longer in order to be absorbed fully by the plant

5. Mulch around the Plants

Mulching has a lot of benefits for your plants. It helps to conserve soil moisture during hot and dry periods, reduces weeds and adds nutrients into the soil after decomposing. It is recommended to apply 2 to 3 inches of organic matter on the soil around your plants.

The best mulching materials for tomato plants include grass clippings, straw, shredded leaves and saw dust. Other materials, like eggshell,s can also be used to mulch around the plants. They release little calcium into the soil as they decompose.

6. Use a Balanced Fertilizer

Tomato plants are heavy feeders, and they require a balanced fertilizer to grow healthy and produce high yields. However, you should avoid over-fertilization, especially with synthetic chemical fertilizers.

Excess nitrogen in the soil can prevent the absorption of calcium by the plants.  Excess ammonium ions interfere with calcium availability. It is recommended to fertilize with compost, a balanced organic granular, fish emulsion, or seaweed emulsion.

7. Keep off the Roots of your Tomato Plants

Damage on the roots during weeding can cause them to rot. This typically interferes with the absorption of  nutrients from the soil. Uproot the weeds that are near the plant gently to avoid root disturbance. Employ other methods of weed control, like mulching, to prevent root damage.

8. Fix the pH of the Soil before Planting

Tomato plants prefer a soil pH that is within a range of 6.2 to 6.8. Proper pH for efficient calcium uptake is 6.5. Calcium. Other minerals in the soil are also readily available for the plant when the pH is at this level. If the pH is above 6.5, you can lower it by using organic mulches and compost fertilizers.

Final Thoughts

Now that you know what causes tomatoes to rot on the vine, make sure to manage and maintain the plant properly by watering deeply and evenly, mulching, avoiding any disturbance on the roots, checking the pH and improving calcium content in the soil.