Flushing your marijuana crop maintains nutrient uptake while cleansing your plants of unwanted build-ups.
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Most gardeners realize the importance of flushing their medical marijuana before harvesting, but many overlook the benefits of a periodic flush. Throughout your cannabis' growing and blooming cycles, it is a good idea to periodically flush the plant’s medium to reduce the chance of a toxic salt build up. I have found that there are key times for flushing that can greatly improve performance, especially if you are using a chemical fertilizer.
Some hydroponic systems contain virtually no growing medium (deep water culture and aeroponics) so flushing these systems is as easy as changing out the nutrient reservoir. Other hydroponic systems that use rockwool, coco fiber or other soilless mediums tend to accumulate salts much like a container of soil and need to be flushed from time to time to ensure optimal performance.
When To Flush
I flush three times throughout the duration of my plant’s cycle. The first flush is during transition (moving from vegetative growth to flowering growth). I like to do the second flush about half way through the blooming cycle. The final flush is seven days before harvest. I will also do a flush anytime I suspect a nutrient build up or see signs of deficiencies. Many deficiencies are caused by a nutrient becoming unavailable because of a salt build-up in the medium, not because you are failing to supplement that particular nutrient.
For all flushes, except my pre-harvest flush, I use epson salts or a diluted amount (1/4 strength) of the fertilizer I am using in that given stage. Epson salts have an amazing ability to leach out natural salts that build up in soil or hydroponic mediums. Epson salts also have the ability to leave behind traces of magnesium which is commonly locked out with salt build ups.
To use epson salts as a flushing agent, mix 1-2 tablespoons per gallon of water and run the solution through your soil or hydroponic system. My second option, 1/4 strength fertilizer, works to pull out excess nutrients because alike molecules tend to bond to each other. A diluted fertilizer will leach out more salts than plain water alone.
For recirculating hydroponic systems, run an epson salt formula or diluted fertilizer regiment for a few hours and then return to your normal fertilizer mixture. If your plants are stressed due to a salt build up or a nutrient deficiency it may be a good idea to refill the nutrient reservoir at 1/2 or 3/4 of normal strength until your plants show signs of recovery.
A week before I harvest my medical marijuana I like to do a final flush. This flush is designed to rid the medium of excess salts, nutrients, heavy metals or any other toxins that have accumulated. There are many flushing agents available at your local hydroponic retailer, but I like Final Phase by Advanced Nutrients. All plants respond differently to a pre-harvest flush and, because Advanced Nutrients is the only company that specifically tests their products for medical marijuana, Final Phase is the only flushing agent I trust to get the job done properly.
For hydroponic systems, I empty my reservoir seven days before harvest and fill the reservoir with water and Final Phase. After recirculating this solution for 8 hours, I drain the reservoir and fill it with plain water. I then use plain water in my reservoir until it is time for harvest. In soil, I feed a solution of water and Final Phase seven days before harvest and then feed my plants plain water when needed throughout the last week.
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Tuesday, 06 September 2011
Article by Lee G. Leissett, on Sep. 7th 2011