Posted on by Jason Gibson

Redux: Flushing

Flushing is a technique used in between feeding weeks to ensure nutrition is available to the plant at all times, it is also used in the maturation (harvest) stage of a plants life. Flushing your plants before you harvest is crucial if you want your crop to be resinous, aromatic and full of flavour.

Flushing your pots or systems free of nutrients allows the plants to consume the remaining nutrients within itself, if all of the plants ‘veins or lines’ haven’t been effectively cleaned, this will result in an unhealthy plant and a much harsher crop that generally tastes like the nutrients you were plugging them with!

Some cleansing products are dedicated to this phase and specialised solutions actively seek out excess salts and convert them back into useable forms for the plant.


Timing is key with flushing

Experienced growers understand the benefits of flushing weekly, this will result in a super healthy plant always consuming fresh nutrients.

Plants that go through life not ever being flushed will go through a myriad of problems only confusing the grower.

At A-Grade Hydroponics we recommend gardeners to flush once weekly in hydroponics and coco based systems.

Think of an un-flushed plant as sitting in a bath that has not been changed for a few weeks, its technically bathing in its own waste!

If you are reading this tutorial because you’re near the end of your flowering phase then follow these steps to ensure you’re not flushing too early.

  • Pay attention to the overall form of the flower and fruit, usually with an 8-week strain, the flowers development starts to plateau around week 6 - 6.5
  • At this time, we massively reduce our nutrient solution concentration.
  • Usually before this transition most growers would have an EC between 1.6-2.4
  • Remove any old solutions and replace with plain water, correcting the pH to 6.0-6.2
  • Most tap water in Australia is between 0.0-0.1 EC
  • Ideal maturation is 0.1-0.3 EC



The key here is to flush the pots until the water is running freely out of the base of the pot, you would then allow the plant to naturally dry up the pot itself, then its rinse and repeat for approx. 7-14 days.



For systems where the roots are permanently sitting in nutrient solution, such as Deep Water Culture. Remove old nutrient solution from tub/reservoir and fill with plain water at pH 5.8-6.0, the plants would then sit in this water for around 7 days until harvest.

Alternatively, some growers prefer to scale down the nutrient solution strength over a two week period until the EC of their reservoirs reach around 0.5 for the final 3-5 days, simulating that of a downscaling coco flush.

 Flushing Tomatoes Harvest

A harvesting tip:

Harvest your plants before the lights are due to come on, this ensures there are no left-over nutrients being circulated through the veins of the plant, remember as soon as light touches them the capillary action re-commences.

Utilising this method will also ensure in maximum terpenoid profile, after a long day of light exposure the terpenoid hydrocarbons evaporate, by harvesting this way you will always have a super aromatic crop!