Blossom end rot in capsicums

Ber capsicum

Growing capsicums is relatively easy and that's why it has picked amongst many farmers especially in urban areas. They don't burn too much of your resources like having to weed them day in day out. You can grow them anywhere even on your backyard as long as there is a good breeze and a bit of direct sunshine, or plant them in pots and place them on your veranda.

Despite being relatively easy to grow them, there are few problems you are likely to face with your capsicums. One of those problems is blossom end rot, a disease caused by insufficient calcium in your crops. Calcium is necessary to help in developing cell walls for the capsicum fruits hence a deficiency in it can be quite catastrophic.


If you notice some dark and rotten spots at the bottom of your capsicums, then know your plants have been infected with this blossom end rot. Those dark and rotten spots you are witnessing are cell walls of the capsicum fruits collapsing due to insufficient calcium supply.

Causes of calcium deficiency on your capsicum fruits

A number of factors lead to this problem. The soil could be lacking calcium in the first place or it has enough calcium which is tied up in the soil due to competition from other minerals. As described by Tony, one of the experienced MFarmers doing green house farming in Kikuyu, Machakos and Kwale, calcium is less soluble compared to some other minerals. Therefore, during water uptake by the plant, those other minerals are likely to take the front seat leaving calcium untouched in the soil.

Another factor is irregular or insufficient water supply in the plant which reduces calcium uptake. For calcium to be absorbed by plant it has to be dissolved in water. Hence if no water available for absorption, then no calcium uptake.

Too much fertilizer application which supports robust vegetative growth making calcium supply unable to catch up. Calcium is less mobile. It takes a while to trans-locate from the roots to the leaves. If you have a plant that is growing really fast, then you have problems as it will take a while before the calcium reaches the leaves where fruit development usually occurs.

Also wrong timing of nitrogen fertilizers applications. If you apply nitrogen fertilizers during fruiting, vegetative growth will be induced and that means calcium will trans locate from the fruits to support this vegetative growth. It will take a while before it goes back to continue supporting fruit development.

How to fix this

Soil tests. You will need PH levels above 6 to beat calcium deficiency and the best way to determine that is by carrying out soil tests. This will give you a clear picture of how much lime to add. If everything is okay with the soil, then based on your soil test results, your soil test service provider will recommended you better alternative sources of calcium to apply.

As suggested by MFarm farmers, you can pay a visit or send your soil samples to a soil testing lab of your choice. KARLO or Soilcares ltd are one of those organizations offering soil testing services.

Check your fertilizer application schedule. Avoid nitrogen fertilizers as soon as fruiting stage sets in as this will trigger vegetative growth.

Keep an even moisture supply in your production environment. Water your plants regularly and apply mulching where necessary. This will keep an active process of absorbing calcium solution to the plant.

Also, applying crushed egg shells to your soils is likely to improve calcium levels in the long run hence limiting your blossom end rot occurrences.

As per suggestion by Tony, applying Calcium fortified fertilizers such as “ARM Mavuno” or Compound fertilizers such as CAN can help fix calcium deficiency. However, the best approach would be spraying your farm with foliar feeds. A good example is the “Grocal” one from Amiran. What happens with CANs and the likes is that they just increase the concentration of Calcium in the soils to wrestle up with the other minerals. This might work well, which is fine. But with foliar feeds, what happens is the calcium is directly injected into the plant via the small holes on the leaves(if you remember stomata). And with calcium being less mobile, you will have enough supply of calcium where it is required for a long time.


It is quite important to do soil tests before you begin planting your crops. Always know your environment well to avoid some surprises. Blossom end rot should not give you sleepless nights as it easy to fix. Applying necessary fertilizers and foliar feeds should do the trick. However, once a capsicum fruit is infected with blossom end rot, just get rid of it as it will not recover. It will be unmarketable and if left in the field, it will just consume more resources for nothing.

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