Flushing cannabis is simply "flushing" the minerals and nutrients out of the soil/ growing media. 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 all of the essential nutrients from the soil.
However, much like humans store fat, plants store excess nutrients in their leaves that they can use later if nutrient levels run low. It's 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 may result in a bitter taste, unpleasant chemical taste, and smell. Without flushing, your cannabis will not be as enjoyable. After putting in months of hard work to grow the plant, you want to make sure you do this simple step to ensure your cannabis tastes as good as possible.
For the highest quality cannabis, it's 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 lockout. Excess salt and nutrient buildups can be avoided by this technique. It also helps in maintaining the PH balance of the soil. This can be done at any point during your grow to ensure nutrient lockout does not occur.
Overfeeding of the cannabis plants may 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. Below is an image of a cannabis plant with leaf tip burn.
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 your cannabis plants is two weeks before the harvest. If the plant has a total of the eight-week flowering stage, the flushing will need to take place six weeks after the start of the flowering stage. Flushing plants before 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 helps to better understand the time of harvest. Once the trichomes are mostly milky white with some amber, it's time to harvest.
How to Flush Cannabis
Flushing by Watering- This method requires running, untreated fresh 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 used 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 of the nutrients have been washed out and how pure the water runoff is necessary. The total dissolved solids (TDS) reader linked above is easy to use, non-technical and is perfect for beginner and advanced growers.
Next, 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. The water running out of the pot should be a brown/ murky color. This is totally normal. Scoop up some of that water to test with the TDS reader, and once it's below 50ppm, you know you have successfully flushed your plants soil/ growing medium!
The only time you should avoid flushing your cannabis plants is if you are using an organic soil with added amendments. Often beneficial microorganisms are added to this soil and can easily be washed away.
With a hydroponic setup, all you need to do is replace the water with fresh water that has been pH adjusted. It's much easier to flush in a hydroponic system than soil.
With a Grobo, it's super simple. Keep up with the reminders of when to drain and fill your unit, and when it's time to flush your Grobo will automatically know not to add nutrients!
Some Disadvantages of Flushing Cannabis Plants
Since flushing means washing out all the nutrients from the roots, there can be disadvantages. While many growers swear by this process, others deem it unnecessary. Here are some of the reasons why some growers do not see the need to flush their plants.
- The loss of useful nutrients in the plants too soon, prevents them from continuing to flower properly. The plants are technically starving since they have no nutrients to use.
- The plant may get shocked by having plenty of nutrients, to no nutrients in a short period of time.
- 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.
- There is little scientific evidence this procedure is effective
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. It is not a mandatory process, however many people swear by it. You could always try flushing and see if it makes a big difference!
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.
Are you interested in reading about other tips that can help you grow the most successful cannabis plants? Click here!
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