Stop Tomato Blossom End Rot

How To Stop Tomato Blossom End Rot Before It Begins!

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Tomato blossom end rot is a common issue that can affect the quality and yield of your tomato harvest. It occurs when developing tomato fruits exhibit a black/brown sunken area at the blossom end, which can ultimately lead to the fruit becoming inedible. Inconsistent watering practices often cause this condition but it is actually a calcium deficiency.

By managing watering practices, using suitable soil amendments, and monitoring plant health, you can achieve a healthy and abundant tomato harvest. In this article, we’ll discuss some strategies to help you stop tomato blossom end rot and enjoy your homegrown tomatoes to their fullest potential.

Blossom End Rot
Blossom End Rot

Possible Causes

Watering Techniques

I can’t stress this enough – the leading cause of blossom end rot is inconsistent watering.

While the issue is a calcium deficiency, it is usually that the plant cannot access the calcium in the soil rather than there not being enough. If your soil becomes too dry then the roots of your tomato plant cannot access the calcium, even if it is there in the soil.

Maintaining steady levels of moisture is crucial in preventing blossom end rot. Tomato plants require consistent and deep watering to establish strong root systems. Follow these watering techniques:

  • Water your plants in the early morning to reduce water loss through evaporation.
  • Water deeply and heavily rather than a sprinkle on the top
  • Apply a layer of mulch to retain moisture and regulate soil temperature.
  • If using grow bags, use a collar to add a reservoir – if you are not sure what I mean, look at the product below.
Less Watering Needed!
Pack of 6 Tomato and Vegetable Growbag Pots
  • Specially designed pot for growing in growbags
  • Set of 6, measuring 26 centimetres across, so three fit neatly on a growbag
  • The inner and outer watering troughs make feeding and watering easy
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03/01/2024 10:14 pm GMT

You need to be cautious and not overdo this, however. This is because too much water also causes a lot of issues with tomato plants, that is why I said they need consistent watering rather than lots of water.

If tomato roots sit in standing water, then they can suffer from root rot, and if your plant has a poor root structure then this can lead too… you guessed it – blossom end rot.

Adding Calcium

You can also add calcium to your soil if you think this is the root cause of the issue.

Crushed eggshells are a common homemade remedy as they are high in calcium. Calcium nitrate fertiliser can be bought and sea shells, crushed and added to the soil can also work. Fish blood and bone is an organic fertiliser that again has high calcium levels.

Providing the right balance of nutrients is vital for tomato plant health and resilience against blossom end rot.

Crush Eggshells With A Pestle and Mortar and add to your soil
Crush Eggshells With A Pestle and Mortar and add to your soil

Over Feeding With Tomato Food

This one doesn’t get picked up on but can actually cause blossom end rot. Tomato feeds are very high in potassium to promote strong fruit growth, but too much potassium can actually cause blossom end rot.

High potassium levels can block calcium and prevent it from being taken up by your plant’s roots. This problem is further exacerbated by unknowing gardens that see the first signs of blossom end rot and think their plant is getting the nutrients it needs – so give it another feed of tomato food.

You can see how this is a vicious circle that can quickly spiral.

Liquid feed out of a watering can.
Liquid feed out of a watering can.

Over Feeding With Nitrogen Feeds

Nitrogen is a common ingredient in many plant foods and is often the main ingredient. It promotes green leafy growth and is good to apply to tomatoes early in life.

However, you want to stop feeding with nitrogen-heavy feeds when they start to flower and fruit. This is because you want the plant’s energy to be going into developing fruits rather than leaves.

Overfeeding with nitrogen-heavy feeds can also cause blossom end rot. This is because leaves are preferred over fruits when it comes to where a tomato plant sends its calcium.

So if you have lots and lots of large leaves still developing and growing – encouraged by the high nitrogen feed – then your plant might not have enough calcium left to send to the fruit, leading to blossom end rot.


In summary, tomato blossom end rot is a preventable condition that commonly affects tomatoes, but can also impact other garden vegetables such as peppers and aubergines. Proper watering techniques and optimal nutrient balance are crucial in preventing this issue from arising in your garden.

Implement a consistent watering schedule and water deeply rather than surface watering. If growing in growbags, then use growbag pots as due to their shallow nature, growbags can dry out quickly.

If you are sure your soil is low in calcium then get a soil test and add some back in if needed.

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One Comment

  1. I have started to use “collars” or halos, even though my tomatoes and courgettes and cucumbers are all planted in raised beds. I think it makes providing water and liquid fertiliser easier and helps keep water off the leaves. All seems to be working fine so far. I believe that this way the water is distributed more equally to all side of the plants

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