How do I treat blossom end rot on my tomatoes?

Q.

Hi, my tomatoes have developed rot at the bottom of the fruit. My other plants appear to be okay. Can you please advise how to stop it affecting my tomatoes? Matt.

A.

The problem is blossom end rot which commonly affects tomatoes, capsicums and courgettes. It is not a disease but a physiological disorder and can't be spread from plant to plant or from fruit to fruit.

See below for causes of blossom end rot and ways to help prevent it:

  • Irregular, uneven watering. Water plants consistently and regulate the watering depending upon the weather conditions.
  • Tomatoes growing in containers (or planter bags) have more chance of drying out - one big water a day is preferable to two light waterings. Take care not to wet the foliage too much. Use SaturAid for container grown tomatoes to ensure that water is evenly distributed through the pot and the potting mix remains moist between waterings.
  • Tomatoes planted early in the season when temperatures are cool are more susceptible to blossom end rot. Early fruit may show signs but later developing fruit should be fine.
  • Tomatoes can also develop blossom end rot due to a lack of calcium and magnesium. Use a fertiliser low in Nitrogen (N) and high in phosphorus (P).
  • As tomatoes grow very rapidly over a short period of time, make sure you feed them regularly, if using a liquid feed do it every fortnight.
  • If you are growing tomatoes in a glasshouse increase the ventilation as high humidity can also contribute to blossom end rot.

 Tui Organic Seaweed Plant Tonic is a seaweed based tonic which is great for tomatoes. 

The good news is if you get the fertiliser regime right and water consistently the blossom end rot will go away. Remove and affected fruit to encourage more fruit on the plant.

Click here for the Tui Tomato Growing Guide >

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How do I treat blossom end rot on my tomatoes? Comments

  • Every year our potatoes get a brown scale, wart like on them. Wondering why? H

    Carol Glidden

  • Hi Carol, this is a very common problem, it is most likely potato scab, often this problem can build up in the soil and if you have it each season and they are planted in the same spot the problem will keep coming back. It can be limited by adding lime to the soil, as it prefers acidic soil. Potato fertiliser will help balance the soil. Try rotating the spot where you grow them if you can. Thanks, Tui Team.

    jenna

  • how to stop blossom End rot

    dennis

    • I switched fertiliser to one that had calcium in it but it didn’t fix the problem. The variety I had grown in the ground successfully (Black Krim) just didn’t like being grown in pots - even very big pots. A hot summers day in NZ means uneven watering and this means blossom rot. In the end I switched varieties (to Mortgage Lifter) and so far no problems.

      Jeff Sole

  • Hi Dennis, check out the answer above. All the best, Tui Team

    jenna

  • Hay matt.with your tomatos with blossom end rot....use some lime...and work it into your soil under your plants then water it in.it works well.scott

    Scott Abbott

  • Thanks for this timely answer. Some of my tomatoes are ripening now and some have the rot at the bottom.

    Daphne Carvalho

  • mix a thick slurry of water & lime and pour around plant away from stem, water this in over a few days.

    Ray

  • I have always grown tomatoes in pots and always had problems with blossom end rot. I now cover the top of the planter mix with a layer of wood pallets or wood pallets cat litter and they hold more moisture. I don't get blossom end for any more, it really works.

    Les

    • Thanks for sharing your tip Les!

      Tui Team

  • I had tomatoes rot but i asked some friends of mine and they gave me copper to spray on them and they told me to put some copper wire cut into short pieces put them through the steams as the it help kill it as my tomatoes are doing well.

    robert king