Blossom End Rot

Blossom end rot is exactly what it sounds like.  It starts with what appears to be a small bruise and slowly develops into full rot on the bottom (blossom/flower end) of your fruit.  It’s most famous for occurring in tomatoes, but it can impact peppers, cucumbers, eggplant and squash as well.  The good news is that it is extremely rare in hydroponics.  It's also not a disease, so it will not spread from plant to plant.  Blossom end rot is caused by a lack of calcium in the fruit, which can be cured by ensuring your plants have the access to calcium that they need.

Now that we know that blossom end rot is caused by a lack of calcium, let’s discuss how to cure it:

  1. Check the EC levels of your hydroponic system. If you’re growing fruiting plants like tomatoes, peppers, eggplant and squash, your EC will preferably be above 2.0.  Lower EC’s can potentially be ok, as described in this article about growing a variety of fruits and vegetables, but risk certain health issues that could include blossom end rot.
  2. Check the pH levels of your hydroponic system. A pH level between 5.8 and 6.5 is best for sustaining the majority of your plants.  If your pH is too high or too low, your plants will be less successful at absorbing nutrients, including calcium.
  3. Adding Calcium to your system is probably going to be the most appropriate step, assuming that your EC and pH levels are being maintained appropriately. A product called CAL-MAG is the most popular in the industry, but there are many calcium additives that you can use to put an end to blossom end rot.  Read the directions, and always start with the lowest recommended dose.  Most hydroponic growing formulas have enough calcium to support plant growth without worrying about blossom end rot, so it is a rare issue to experience.  But, it can happen when growing lots of fruiting plants.  Keep in mind that when you add calcium, the fruit currently experiencing blossom end rot will not improve, but new fruit should not succumb to it any further.

Blossom end rot is not a disease, you don’t have to worry about starting new plants.  Simply make sure that your EC and pH levels have been consistently in range so that your plants have been able to absorb the calcium they need.  If so, adding Calcium is likely to be the solution for you.  Start with low amounts of calcium and climb as necessary.  You’ll be growing delicious fruits again in no time.

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