Dealing with Blossom End Rot

You’ve carefully planted your tomato seeds, nurtured them throughout the spring, and now you’re finally starting to see some tomatoes forming! But what’s this? There's a disgusting black scab growing on the bottom of your beautiful tomatoes.

That awful scab that’s ruining your tomatoes is called blossom end rot or BER for short. 

What is BER and how can I identify it?

BER rot is a physiological condition that may occur in vegetables such as tomatoes, peppers, melons, eggplants, squash and cucumbers. 

BER symptoms can occur on both green and ripe fruits and is identified by a brown or yellow water-soaked spot which gradually appears on the end of the fruit where the blossom once was. In many cases, secondary pathogens, which appear as a black, fuzzy-like growth, attack the affected area and will eventually cause complete rotting of the fruit. 

What causes BER?

BER is most often caused by uneven watering or by a calcium deficiency.

Don't be too alarmed, we've found this to be somewhat common with the first batches of tomatoes and other crops. Please note that there are other reasons why your crops may have BER, but we've chosen to focus on the most common.

Does BER Spread?

BER does not spread from plant to plant, however plants growing near each other may all be affected, since they all share similar growing conditions.

Are tomatoes with signs of BER safe to consume?

If the rot spot isn't too large, you can trim off the damage and eat the rest of the tomato. It is however important to make sure to trim far away from the spot, because the rotten taste can spread beyond the visible damage. In some cases the tomato is too far gone to salvage. 

Can I heal the tomatoes with BER?

No, you cannot heal a tomato with BER. Best to focus your attention towards prevention and control measures to salvage the plant and any remaining tomatoes it produces.  

How do I prevent or treat BER? 

1. Add calcium

While egg shells are great, their calcium will not be absorbed by the plant until they start decomposing. Instead, we suggest mixing non-fat powdered milk into your watering can for a quick hit of calcium. Alternatively, you can add bone meal to your soil as it supplies calcium as well. 

2. Be consistent with your watering

Try to water your crops at the same time of day and only water when the soil is dry. Watering in the early morning is best, because the crops have all day to soak up the water. If watered in the late afternoon or evening, the soil may remain wet overnight which can result in fungi developing.

With the hot and humid summer we've been experiencing in our region we've noticed that inconsistent watering has also been a major cause of BER. Either too much water or not enough water (or rapid swings between the two conditions) can trigger BER. In fact, we've found that the rain we've been experiencing late in the day seems to aggravate BER.

3. Use fertilizers that are low in nitrogen

Avoid using high nitrogen fertilizers which accelerate vegetative growth and reduce the uptake of calcium by plants. We recommend you use fertilizers that are low in nitrogen and high in phosphorous, such as Botanix's Tomato and Vegetable Fertilizer (6-10-14).

4. Choose tomato varieties that are less susceptible to BER

It is said that some varieties are more prone to BER including San Marzano and Better Boy, however Celebrity had a low incidence of BER.

5. Cut your losses

We recommend you pluck all tomatoes with any signs BER and throw them in your compost. Why allow your plant to waste its energy on growing an unhealthy tomato, when it can redirect its energy towards healthy new growth.

If you have any follow up questions, don't hesitate to ask!


What proportion of non-fat powdered milk do I add to water when trying to combat BER?

Coleen July 28, 2020

Thanks for this, I just noticed it on one of mine and was wondering what was going on. I wish we could just have the odd day of gentle rain rather than the drought/downpour cycle we’ve been having.

Sarah July 28, 2020

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