Tomatoes Rotting on the Vine? Reasons and How to Fix

It is distressful to notice a 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. So, why are your tomatoes rotting on the vine?

Tomatoes rotting on the vine is commonly caused by blossom end rot. This disorder 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.

Blossom end rot predisposing factors include inconsistent soil moisture content, root damage, excess soil salinity, and deficiency of calcium in the soil. It is a serious condition that results in tomatoes dropping off the vine.

Tomatoes rotting on the vine

Why are my tomatoes rotting on the vine?

Tomatoes rotting on the vine mainly results 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 leathery spots.

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 peppers or eggplants.

Blossom end rot results from an insufficient amount of calcium in the fruit. Inadequate amounts of this mineral in the plant tissues result from poor absorption or 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 from the soil to prevent it from blossom end rot and other conditions. Several factors can limit the ability of tomato plants to absorb enough calcium. They include:

Inconsistent soil moisture content

Blossom end rot is common when there is heavy rainfall that is followed by an extended period of dry weather. It can also happen if you are not watering your plants correctly. As you know, inconsistent watering may also result in tomatoes splitting on the vine.

Calcium is transported within the plant only when there is ample supply of moisture. When the plant is not receiving enough water, the fruits may continue to grow but will suffer from calcium deficiency.

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 lack of aeration.

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 a sufficient amount of calcium quickly enough to satisfy the demand.

Insufficient amount of calcium in the soil

Inadequate calcium in the soil is also characterized by blossom end rot in tomatoes. Plants require calcium and other minerals from the soil to grow rapidly and produce quality fruits. Calcium deficiency can be determined through a simple soil test. Its deficit can be corrected by adding lime to the soil.

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 fruits develop fully. The absorption of calcium also reduces when nitrogen is applied in the ammonium form. The ammonium ions compete with calcium ions for absorption by the roots.

Excessive soil salinity

Increased salinity decreases the amount of calcium absorbed by the plant. It also decreases fruit calcium content by restricting the amount of water absorbed by the plant. The 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 to fix blossom end rot in tomatoes

Blossom end rot is physiological in nature. Therefore, it cannot be controlled by the use of fungicides. It is recommended to use the following tips to control:

1. Choose a resistant tomato Variety

When intending to plant tomatoes, it is always important to choose a variety that is resistant to various problems such as blossom end rot. There are numerous tomato varieties, some are more prone to blossom end rot as compared to others.

Tomato varieties that are more susceptible to blossom end rot include Better Boy, Orange Banana, and San Marzano. On the other hand, Blue Beauty, Black Cherry, Amish Paste, Opalka, Arkansas Traveler, Glacier, Stupice, and Mortgage Lifter are among those that are less affected by blossom end rot.

According to a scientific research conducted by the University of Illinois, they found the following tomato varieties with less incidences of blossom end rot: Celebrity, winter, Sunny, Mountain Pride, Jet Star, Fresh Pack, pink Red, and Manapal.

High chances of this problem were reported in various varieties that include: Big Boy, Independence, Fantastic, Whopper, Supersonic, Wonder Boy, Surprise, and Castle King.

2. Maintain the correct amount of 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 and hence increasing the chances of blossom end rot.

Tomatoes planted in containers are likely to suffer from this problem due to the inability to keep the soil moist enough. However, you can try using self-watering containers to ensure the soil has the correct amount of moisture. Provide drainage holes at the base of the containers to get rid of excess water.

3. Improve calcium levels in the soil

Improving calcium levels in the soil can actually fix the problem of blossom end rot. There are several ways to achieve this; instead of tossing those eggshells into the garbage bin, you can use them to improve the calcium levels of your garden soil. Eggshells are rich in calcium together with little potassium.

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. Alternatively, you can mix the powder with soil in the planting holes prior to transplanting your seedlings.

Other materials that are rich in calcium include bone meal, oyster shell, or gypsum. They help to prevent blossom end rot in tomatoes when added to the soil. 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. Apply a layer of mulch around the plants

Mulching has a lot of benefits for your plants. It helps to conserve soil moisture content during hot and dry periods, reduces weeds, and adds nutrients to 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, straws, shredded leaves, and sawdust. Other materials like eggshells 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 plant.  Excess ammonium ions interfere with calcium availability. It is recommended to fertilize with compost, a balanced organic granular, fish emulsion, or seaweed emulsion.

7. Avoid disturbance around the roots of your tomato plants

Damage to the roots during weeding can cause them to rot. Damaged roots will not be able to absorb the necessary nutrients from the soil and hence the fruits are likely to suffer from blossom end rot.

Avoid using a hoe near the plant roots. 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. Check the pH of the soil before planting

Tomato plants prefer a soil pH that is within a range of 6.2 to 6.8. However, the proper pH for efficient calcium uptake is 6.5. Calcium and other minerals in the soil are 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. Managing tomato plant properly help to prevent future occurrences of blossom end rot.


Blossom End Rot – Iowa State University

Rotten Tomatoes – North Dakota State University

Growing Tomatoes – Washington State University

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