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 pots or systems free of excess nutrients allows for a fresh feeding schedule to maintain accurate levels. When it comes time to final harvest, if your plants haven’t been effectively 'cleaned', you will have built up nutrients and carbohydrates still within the plant's pot, resulting in a much 'harsher' crop that generally tastes like the nutrients you were plugging them with!
Tailored solutions like Terra Aquatica FlashClean are designed to be used in between feeding weeks, these specialised solutions actively help dissolve mineral deposits in the grow medium to flush out, aiding in your root zone efficiency and health.
Timing is key with flushing.
Experienced growers understand the benefits of flushing regularly, this will result in a super healthy plant always consuming fresh nutrients in the right quantities. 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 regularly in hydroponics and coco based systems. This could be once every 1-4 weeks to maintain pot nutrient equilibrium.
Flushing Toxic Build-up (Mid-Grow Flushing)
A common issue but almost always mis-diagnosed that many hydroponic growers using coco mediums will run into during their first few grows, is a toxic build up and accumulation of mineral salts within their medium. This is rather common for growers that use hydroponic nutrients, allowing a slow creep up of medium EC and huge pH swing as a result, which can be devastating or even fatal to the plant if left unchecked. Terra Aquatica FlashClean is an excellent solution for this particular issue.
How will I know if I need to flush mid-grow?
For the best and most accurate results when growing using hydroponic nutrients, you should be measuring your run-off from your plants every day, at minimum once every 3 days.
'Run-off' is the excess liquid that will run out of the bottom of your pot after a feed, measuring this liquid will give you a good idea of what the pH and EC is actually like in your medium. If you are feeding your plants a 1.5 EC, 6.0 pH solution and the run-off is measuring 2.1 EC and 5.3 pH, then your medium is likely in a toxic state to the plant and sitting in an acidic pH environment. This will cause nutrient lock-out and stunt growth, eventually killing the plant over time.
This has occurred because the grower has been feeding too many nutrients to the plant that it was unable to consume before the next feed happened, building up an excess of mineral salts (nutrients) in the medium.
To correct mineral salt build up in the medium, the answer is to flush the pot and medium using plain water to dilute and clean out all the accumulated minerals. You can also use great flushing products like Terra Aquatica FlashClean or Hyclean to help with the efficacy of the flush. To do this, simply flood the medium with plain water (or with a flushing product) and measure the run off, repeating this process until you have a run-off reading in the pH and EC/PPM in a range you are happy with for that particular plant.
In the case above, you are trying to feed 1.5 EC / 6.0 pH to your plant, but your run-off is reading 2.1 EC / 5.3 pH, you would want to flush your medium with plain water repeatedly until the flush runoff is reading a safe range, such as 0.5 EC / 5.8+ pH. This may take several flushes and lots of water to achieve. If you were to skip the flush and feed this toxic pot with your 1.5 EC / 6.0 pH solution, you would end up increasing the EC in the medium even further into toxic conditions and killing your plant at a faster rate.
The Final Flush (Harvest Flushing)
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 1.5-2.0
Remove any old solutions and replace with plain water, correcting the pH to 6.0-6.2. You can also benefit this process by using flushing products to help dissolve the remaining salts that have built up in the pot for faster flushing.
Most tap water in Australia is between 0.0-0.1 EC
Ideal maturation is 0.1-0.3 EC
For systems where the roots are permanently sitting in nutrient solution, such as Deep Water Culture, the flush of these systems are the easiest and fastest, as no build-up of nutrients can occur in the medium. Start by removing 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.
Flush your plants for better end results when using hydroponics nutrients!