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Flushing Cannabis - Steps and Benefits

Bjorn Dawson February 24, 2020


The process of flushing cannabis, means leaching out minerals and nutrients in the soil and the root zone using plain water or other flushing agents. This process can be carried out during your grow, but is most common when you are in the last week or two and almost ready for harvest.


Some people raise questions regarding the effectiveness of flushing because this process seems to rob the soil of all the essential nutrients.


However much like humans store fat, plants store excess nutrients in their leaves that they can use later if nutrient levels run low. It is actually very important to understand how significant a role flushing plays in growing cannabis.



Why is the Flushing of Cannabis Plants Helpful?

● The removal of nutrients from the root zone right before harvest makes the cannabis plant focus on using up any remaining nutrients present. 


If the remaining nutrient reserves are not used up by the plant, the quality of the end product will be affected. It will result in a bitter taste, black ash, unpleasant chemical taste, and smell. 


● For better development of your crop, it is very important to keep changing and clearing out the old nutrient supply. It needs a fresh supply of various nutrients during different phases of growth and flowering.


● Flushing cannabis plants during the grow helps with nutrient lockouts. Excess salt and nutrient buildups can be avoided by this technique. It also helps in maintaining the PH balance of the soil. 


Overfeeding of the cannabis plants is said to result in the tips of the leaves changing color and shriveling up. This occurrence is commonly known as tip burn, and indicates your plant has maxed out its ability to use the nutrients you are providing. 


● Flushing the plants two weeks prior to the harvest is done in order to eliminate fertilizer residues. Removal of fertilizer from the plant roots and the tissues is a crucial step for a final product that is safe to consume and that retains the flavor. 

When Is The Ideal Time To Flush Cannabis Plants?

The usual time to flush the cannabis plants is two weeks before the harvest. If the plant has a total of the eight-week flowering period, the flushing will need to take place six weeks after the start of the flowering stage. Flushing the harvest at the right time helps in enhancing the quality and adds to the smoothness of the buds. 


Two weeks before harvest, the plants are given only plain pH adjusted water. All growers, regardless of the growing media being used, should use this effective method of flushing.


Keeping an eye on the trichomes of the plants helps to better understand the time of harvest. The change in the color of the trichomes from a clear to a milky-white color is an indication of the plants to be flushed immediately.


Sticking to this process keeps getting easier with time and adds to the experience of the growers!

Ways and Means of Flushing Cannabis

Flushing by Watering- It requires running untreated fresh tap water through the soil and leaving it to stay for some time for the nutrients to be picked up. The only thing that is to be kept in mind is the water required to flood the soil has to have a safe pH level for the plants. It has to be between 5.5-6.5 (for hydroponics) and 6.0-6.8 (for soil).


The soil needs to be flushed for the second time for the nutrients to be washed out. The use of a TDS (total dissolved solids) reader to determine how much nutrients have been washed out and how pure the water runoff is necessary.


Collect and measure the runoff of your flush if growing in soil. Continue flushing with fresh water until you are seeing a reading of under 50 ppm (parts per million). This indicates you have removed enough salt for the flush process to begin. 

Some Disadvantages of Flushing Cannabis Plants

● Since flushing means washing out all the nutrients from the roots, this process has the potential to destroy a plant’s root system. Flushing can sometimes prove to be counter-productive if done too early.


The loss of useful nutrients in the plants too soon, prevents them from continuing to flower properly. 


● Some enzymes that protect the root system of the plants by guarding them against molds, pests, fungus etc., get washed off by the process of flushing cannabis. Therefore this process makes the plants more susceptible to root-rot. 


Drawing A Conclusion Regarding Flushing Cannabis

The main objective of flushing cannabis is the expulsion of chemical build up in the plant tissues by making the plant’s process excess nutrients without the storage of unnecessary minerals.


The taste of cannabis can be greatly affected by the simplest techniques. One of the most basic steps to get potent and better-tasting weed is flushing. Use it as one of the tools in your growers handbook, you will be glad you did.

Still have questions? Ask us below.

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