Why & How To flush Your Marijuana Plants?

Some growers claim that flushing is of the utmost importance as marijuana wouldn’t even taste good without a good flush. Is that really true? Is it always paramount to flush your marijuana? Yes and no. In this article, we will shed light on the subject in order for you to know whether or not you should flush your plants and how to do it correctly.

What is flushing?

Flushing means rinsing out the nutrients present in the growing media with high amounts of plain water or water containing a very mild nutrient solution.

Why Flush Your Marijuana Plants?

There are 2 reasons why growers flush their cannabis:
1) to eliminate nutrient build-ups.
2) To get rid of residual nutrients left over in a plant before harvest.

Persian Prince Fading Nicely

Adding more is not always a good idea as it can interfere with the uptake of other nutrients.
Your plants are starting to show signs of over-fertilization? Don’t throw them away just yet! There is still hope. In most cases, flushing your soil AKA leaching the soil with large amounts of water can make your plants great again!
The longer the plants suffer from over-feeding, the harder it is going to be to fix the problem. Consequently, as time goes by, more and more roots will be damaged and the plants will start to burn, turn yellow or wilt and eventually die.


Leaching is a type of flush you can do at any moment during a plant’s life-cycle. It consists of reducing the concentration of dissolved minerals in the growing medium. Therefore, you need to leach your soil if you have increased your fertilizer dosage and are noticing the first signs of nutrient overdose. For instance, overly dark leaves, leaf clawing or tip burn are prime examples of a nutrient overdose. Test the water runoff with an EC meter to confirm whether you need to leach a plant.

Digital EC Meter

EC & TDS meters help measure the salt concentration in the water

How To Flush Properly

When leaching or flushing your marijuana plants, use 2 to 3 times as much water as the volume of the plant containers.
However, growers should still add a mild nutrient solution to their water when leaching their plants. It may seem strange but leaching with pure water can cause the plants to suffer from an osmotic stress (A sudden change in the solute concentration around a cell). However, a 1/3rd-strength nutrient solution will do the trick and prevent that problem.
Should you decide to grow your plants 100% organically, you will need to leach your plants only if they have been over-fed. However, if you are feeding your plants with mineral/synthetic nutrients, do this periodically throughout the plant’s life cycle.

Pre-Harvest Flush

If you have been using chemical nutrients, you absolutely need to flush your marijuana plants!
The final flush or pre-harvest flushing however differs from leaching. During the pre-harvest flush, only give your plants plain water with no nutrients or additives whatsoever.
When growing in soil or coco, start flushing 7 to 14 days before the harvest. However, if you are growing hydroponically, you only need to flush for the last 4 to 5 days. Although you won’t be adding anything, make sure your water is still at the right pH.

Flushing Your Marijuana

Flushing Organic Cannabis?

Despite the aggressive marketing done by some companies with the view to selling more useless supplements, organic soil growers need not worry about flushing.
Indeed, organic soils are composed of microbial colonies and natural enzymes that service plant requirements. Hence, flushing before the harvest would not do the plants any good. That being said, allowing the plants to fade will help you get rid of some of the Chlorophyll thus improving the final taste.  That is why, organic gardeners like to give their plants nothing but water for the last 1 to 2 weeks.

Bottled Nutrients VS No-till VS Supersoil

If you are growing your medicine organically in a rich soil such as a super-soil, no need to flush your marijuana at all!  Likewise, in a “no-till” setup, growers should not flush their cannabis. On the other hand, with organic bottled-nutrients, flushing isn’t important either but it is preferable to stop using them in the last week before harvest. Indeed, the soil is still rich and the plants no longer need an extra source of food at that point. Moreover, keep in mind that giving your plants plain water is not the same thing as a thorough flush.


Countless cannabis growers talk about flushing. It’s all over the internet! The idea behind it is that flushing can help the plants get rid of the residual nutrients left over in the plants . As a result, failing to do so would produce nasty-tasting buds. This is actually true though it only applies to chemically grown marijuana.