Why Are Bottom of Tomatoes Turning Black: Blossom End Rot

Homegrown tomatoes are a delicious treat, tasting several times better than the ones you’ll find on the shelves of a grocery store or a supermarket. If you’ve never tasted a juicy, ripe, freshly harvested fragrant tomato from your garden, you’re missing out on the most authentic taste of one of the most delicious fruits.

Cultivating tomatoes at home is really convenient and super easy. However, it comes with its own set of difficulties. People often report issues with the growth of their tomato plants such as pest infestations, fungal diseases, and cracking of the skin.

One such problem that has been a serious concern for tomato gardeners is the issue of end blossom rot or a water-soaked spot at the blossom end of the fruits, which is quite a common problem with these plants. So what should I do when my tomatoes are rotting on the bottom? This article will provide the answer. But first, let’s go over some basics of tomato farming.

Also Read: My Tomato Seedlings Stopped Growing?


Rich in minerals like folate, magnesium, iron, potassium, zinc, choline, and phosphorus and vitamins A, C and k, tomatoes are good for skin and bones. They are useful in the prevention of diabetes, asthma, heart diseases, and are also thought to aid in cancer prevention. Cultivating such a useful fruit in your own garden is a double benefit as that ensures the consumption of only healthy and fresh fruits.

This delicious, packed with benefits, the fruit is very versatile in the kitchen. You can use it to add a flare of flavors to your curries, make salads, or even enjoy it raw. Cooking without tomatoes is beyond imagination. Once you have tasted the flavors of your own homegrown tomatoes, you are never going to be satisfied with the bland tomatoes from supermarkets that are bred for firmness and longer shelf life.

It is always best to grow tomatoes from seeds at home as that gives you a larger variety of plant breeds to choose from. Tomato plants need well-drained loamy soils and good nourishment to grow properly. They are sun-loving plants that need six to eight hours of direct sunlight. These plants are susceptible to a large variety of pests and diseases and need constant, vigilant care.

Also Read: Will Spinach Grow Back After Cutting

Blossom End Rotting in Tomatoes: WHY? Know your Problem

One problem of being a home gardener, especially a new one is a constant fear and confusion regarding plant diseases that one might not be aware of. Noticing pests or black spots or retarded growth of your plants one fine day can be a cause of confusion and panic, especially with tomatoes, as these plants are infamous for their susceptibility to diseases.

Ever noticed a tomato that looks rotten on the bottom or has a black spot at the blossom end of the fruits? This is known as the blossom end rot. They look like water-soaked spots and appear in half-grown fruits early on in the season. So what should I do when my tomatoes have a black bottom? Keep reading to find out.

End blossom rots are not a disease but a physiological problem arising from calcium deficiency in the tomato plants, leading to the formation of dark, brownish spots at the bottom of the fruit, where the blossom once was. This spot keeps growing larger, darker, and leathery as the plant grows, at times even covering half of the full-grown tomatoes. This is a common garden problem seen in other plants like squash, pepper, eggplants, melons, and cucumber.

In this condition, the tissues on the bottom end of the fruits break down and start rotting. It happens when the fruits are still green or ripening and therefore generally affect the first fruits of the plants. The initial symptoms include a small, water-soaked, soft spot at the opposite end from the stem. This then grows into a black leathery area reducing the overall productivity of the plant.

Some bottom end rot is common especially during the initial days of the season. If the rot is in a small region, it can be trimmed and the tomatoes can still be consumed. However, if the problem persists and takes a greater size, it can become a serious problem for your garden.

What Causes of Blossom End Rot?

Now that you’ve already read enough about the nature of blossom end rot and gained enough insight regarding what they are, it is time to talk about the causes of blossom end rots in tomatoes. Blossom end rots are caused due to calcium deficiency in the plants. Since calcium acts as the binder for the tissues for the fruits, a lack of calcium causes tissues to rot.

This lack of calcium is mostly blamed on the soil’s calcium deficiency either due to depletion, displacement by transpiration, or due to poor drainage. But in reality, it is highly unlikely for the soil to lack calcium and even if that was the case, plants could take up the required amount of calcium from the water.

 A more logical explanation can be the inability of the plant to take up calcium. At times, due to a number of reasons, plants lose their ability to take up calcium from the soil at a sufficient rate according to their changing needs.

Must Read: How and When to Harvest Potatoes in Containers?

Other common causes for this can be:

Over or under watering:

Uneven watering or reduction in the moisture content of the soil can cause a lack of calcium in the plants during fruit formation. Water in the soil forms a chief source of the required calcium. Lack of water also hinders the process of carrying calcium found in the soil to the plants.

Excessive water is also harmful to tomato plants. Of course, the plants need water to thrive, but excessive water can even kill the plant. Overwatering hinders the process of absorption of the necessary minerals, including calcium through the roots of the plant.

Stress on the plants:

Sudden rapid growth of the plants either because of fertilizers or any other reason causes the plant to go under stress as they cannot absorb as much water and minerals as they need from the soil. This makes them unable to cope with the requirements inside their body. In a stressed state, the plant loses its ability to absorb enough calcium and process the calcium that has been absorbed from the soil. This is the reason the first few fruits of a tomato plant are commonly rotten at the bottom end.

Damage to the plant roots:

Another common cause of this physiological defect in plants can be damage to the roots during planting which makes the plants unable to take up the right amount of minerals from the soil. This can happen either during transplanting them from the nursery or initial pot, during weeding, or at any other point of time during the initial days.

Too much fertilizer:

Overuse of fertilizers can damage the nitrogen balance in the soil, making too much nitrogen available to the roots. This hampers the plants’ absorption capacity from the soil.

Other factors such as improper soil pH levels, high salt levels, cold soil, and fast climbing temperatures can also contribute to this problem. An over caring gardener who practices overwatering and overuses nitrogen is really harmful to tomato plants. Your plants only need you to provide as much care as they need, over caring can lead to damage.

How to Prevent Blossom End Rot?

Now we shall come to the next important segment of this article- preventing blossom end rot in tomatoes. Once your plants have borne fruits with blossom end rot there is nothing much you can do as the rot will not go away once the fruit is already affected. But you can prevent it from spreading to other fruits by taking proper care.

The only thing you can do to improve the situation is to take good care of your tomato plants. All you can do is nurture and nourish them well to make sure they have healthy growth. Follow the pieces of advice given below to take better care of your plants.

  • Has your soil tested regularly to make sure it is not deficient in calcium? If you are using a soil bought from the store it is likely to have more than enough calcium in it already. However, if you are using an older soil, chances of calcium depletion become higher.
  • If your soil is deficient in calcium you can add an organic source of calcium, such as lime, bonemeal, and eggshells.
  • You might be tempted to fertilize your soil more since this condition is caused by calcium deficiency. However, in most cases, the soil already has enough calcium. Therefore, over-fertilization just adds to the problem. Instead of trying to fertilize the soils try tending to the plants, as in most cases, the problem arises because they have lost their absorption capacity.
  • Avoid digging or cultivating other plants near the roots of your tomato plants as this can damage the roots. Damaged roots affect the plants’ ability to absorb water and nutrients.
  • Avoid watering your plants too much or too little. Instead, try to maintain a consistent and even practice of watering.
  • Plant tomatoes in a timely manner and make sure the soil is well-drained. Add organic matter to the soil that will lead to the healthy growth of the plants.
  • Avoid over-fertilization. If you do have to fertilize, use a fertilizer that is lower in nitrogen content. Apply only the recommended quantity.
  • Check the pH level of the soil on a regular basis and make sure it is about 6.5. Improper pH levels can be a major cause of blossom end rot.
  • Use mulch to prevent evaporation and maintain the consistency of moisture in the soil.

Blossom End Rot in Tomatoes Cultivated in Containers

If you are cultivating tomatoes in a container you probably have more to worry about than the others. Blossom end rot on tomatoes grown in containers is more common and can be a major cause of concern. However, the solution to this complicated problem is as simple as regularly watering your container.

Tomatoes grown in containers are more susceptible to this condition because they dry out more quickly. Calcium from the soil is delivered to the fruits through the water taken up from the soil. Water is also a rich source of calcium for the plants. Therefore if your plants are not watered well enough, they become more prone to this problem.

If your soil dries out, the plants won’t get enough calcium resulting in blossom end rot. The only solution to this is to make sure that your soil is well moisturized. Prevent the wilting of the plants at all costs.

Water your tomato plants at least once a day. If the weather is hot, you might have to water them more than once. The goal is keeping the potting soil moisturized enough. However, do not overwater since overwatering has its own side-effects.

The choice of the container also plays a major role. Small containers dry out more quickly because of their limited capacity. Dark color containers absorb and retain heat which causes them to dry out, too. Also, be sure to shield the plants from excessive heat to prevent wilting.

The pots you use to plant tomatoes should be as big as possible, preferably holding more than 5 gallons of soil. Light color plastic pots are preferable so that you can easily move them into the shade when the sun is too strong. It is also advisable to place a screen between the plant and the direction of sunlight. 

Even though calcium deficiency is considered the major cause of blossom and rot, magnesium deficiency can also be a secondary cause. Epsom salts can help you in this as they provide magnesium. However, do not use more than one tablespoon of Epsom salts in one-gallon water. Spray this mixture on the plants’ foliage to prevent magnesium deficiency.

In conclusion, it can easily be said that blossom end rot is one of the major problems of cultivating tomatoes, at home, or otherwise. To prevent this, all your plants need is proper care. It is always advisable to oversee their growth every day, keeping track of their development. With the right care and nourishment, you can easily prevent this problem just like you can prevent any other.