Growing Tomatoes - Preventing Blossom End Rot

Blossom end rot is one of the most common problems that tomato growers encounter. Our Gardening Angels take a closer look at the causes and solution.

How To Prevent Blossom End Rot Tomatoes


If you spot the symptoms early then there are actions you can take to save the rest of your crop.

The first sign is a circular spot on the bottom of a developing fruit, which gets larger and darker ultimately turning up to half the fruit a dark leathery brown.

Affected fruits will not recover and need to be discarded, but if steps are taken to remove the stresses on the plant then the next tomatoes to set should be unaffected.

Did You Know?
Blossom end rot can also affect peppers, aubergines, cucumbers and melons.



Blossom end rot is not caused by a disease so can’t be cured with pesticides. It is caused by lack of calcium getting to the fruit.

This can be as simple as lack of calcium in the soil or compost but more often it is caused by the roots’ inability to take up the calcium and move it around the plant. This is often down to drought stress but can also be triggered by other environmental stresses, such as soil acidity or over feeding.


Prevention is the best cure so regular and even watering (especially during fruit set) is the best way to avoid getting blossom end rot in the first place and a good way to restore the health in plants that have suffered from drought.

Self-watering planters like our Quadgrow or Duogrow Planters can provide your thirsty tomatoes with up to 14 days watering, and will take up water as and when they need it thanks to the SmartReservoir and FeederMat system. The soil is never too dry or waterlogged and roots also have better access to oxygen, which fuels faster growth.

quadgrow self-watering planter 

An automated watering system, such as our Click & Drip, is perfect for giving regular and even watering to tomatoes in grow bags, raised beds, borders and veg plots. The slow drip irrigation rate of the Click & Drip gives the soil chance to absorb the water rather than it forming puddles and evaporating or running off. Perfect when you are too busy to pop down to your plot every day.

Did You Know?
Mulching can prevent soil from drying out by retaining moisture.


If you are growing in garden soil then a pH soil test kit can be used to determine the acidity. If the pH is too low (acidic) then adding lime (calcium carbonate) will solve the problem, but keep in mind this needs to be done at least 8 weeks before planting.

In a glasshouse spraying with a foliar feed containing calcium can help to alleviate the problem on established plants.

Don’t be tempted to add extra nitrogen or magnesium as this can make the problem worse by further unbalancing the calcium ratio.

Avoid varieties that are known to be susceptible to blossom end rot. Cherry tomatoes seem to be less susceptible than larger types and plum tomatoes seem to be most affected.

Further Reading
For more information on growing tomatoes, watering and ideal temperatures, read our tomato growing guide.


Need further help?

Our Gardening Angels are here to help you grow strong, healthy plants with bumper harvests. Please do not hesitate to get in touch with any questions on 0845 602 3774 or drop us an email at We’re always here to help!