During the cannabis plant’s life cycle, it uses nutrients such as nitrogen, phosphorus, potassium, salts, and minerals. Most growers feed their plants these nutrients in order to boost growth potential. Nutrients and compounds build up in the plant through the plant’s root zone, and this can lead to harsh smoke and bitter aftertaste. Because of this, many growers have included flushing in their cultivation procedures. The term flushing in the world of cultivation means to rinse away excess nutrients and build up in the root zone of the soil or growing medium that the plant lives in. Like humans, plants too need to be detoxed, so to speak, and flushing is a way to do that.
Some cannabis cultivators believe that flushing the plant’s root zone is needed for the plant’s overall health. Other cultivators say flushing is only needed if the plant was overfertilized. The cultivators focused on the experience of smoking cannabis say that flushing before harvest will help cure a satisfying end product without the harshness that makes smoking itchy with coughs. The debates about the importance of flushing cannabis plants is all over the internet.
To get insight on flushing, I chatted with Monique Robinson, an Oklahoma-based cultivator with an analytical chemistry background pre-cannabis. Robinson is co-founder and co-owner of Kemistry Farms (kemistryfarms.com), a 13,500-square-foot indoor, minority-, family-, woman-, and veteran-owned cannabis cultivation in Okmulgee, Oklahoma, about 40 miles south of Tulsa. The Kemistry team has 13 years of combined experience in cannabis cultivation. (The name of the town, ‘Okmulgee,’ is from the Mvskoke word ‘okimulgee,’ which means “boiling waters’ due to nearby rivers and springs.)
What’s your method for rinsing away excess nutrients and buildup in the root zone?
We use an alternating method. We feed the plants nutrients one day, and water the next day. This helps prevent buildup. We also utilize the traditional flushing method when needed. For instance, if someone accidentally gives the plant too many nutrients that causes the plant to begin to die, you can flush the soil by using tap water to drench the soil until the water runs clear through the bottom of the container. The bigger the container, the more water you will have to use. It’s as simple as that. If you want to be more technical, you could test the tap water for metals before using or use distilled water to flush the soil.
Is it the same method for cleaning up the soil or growing medium?
It is not the same method for cleaning up the soil. Flushing is for the plant’s root zone and consists of using pH-balanced water to drown the soil to help wash away excess nutrients, and other compounds. It requires more than water to clean up the soil. Soil cleaning takes things like biological treatments, chemical oxidation, and/or immobilizing agents.
How often and in what stages should a cultivator flush their plants?
A cultivator should flush their plants one to two weeks before harvest. So, if the plants have an eight-week flowering stage, you should flush the plants six to seven weeks into the flowering stage. When growing indoors, flushing is a signal to the plant that it’s almost at the end of the flowering stage. It allows the plant to uptake the remaining nutrients that are left in the soil, and will help create a better overall product
The pH balance of the water is very important for the optimal health of the plant. The ideal pH is 5.8 to 6.2. You have to remember that a plant is a living thing. If your body’s pH was off, an environment for disease would be created. It’s the same with plants. If their pH is off they can become more susceptible to disease and pests and may become more prone to die
How does a cultivator get their water/rinsing agent PH balanced?
We utilize pH up and pH down solutions to get the water/rinsing agent to the desired pH. We are steadily trying to get our procedures down to science so we can know the exact amounts of reagents to use so that we can minimize using the pH balance solutions.
Some cultivators say there is no benefit to flushing. Others say there are many benefits. What say you?
We have the understanding that it allows the plants to uptake any excess nutrients that may remain in the soil. It allows for a smoother smoke, a better taste, and a better overall product. Flushing can be beneficial in every stage of the plant. If the plant is fed too many nutrients, flushing will help prevent nutrient burn, or lockout. It will assist in washing away buildup around the roots which can cause the plant to die if it is left untreated.
Do you think a different flushing technique/ timeline is needed for indoor versus outdoor plants?
I think the techniques and timelines should be the same whether indoor or outdoor.
What three tips can you share with the aspiring and/or very new cultivator about the first four weeks of the plant cycle?
(1) Have some PATIENCE. Rome wasn’t built in a day.
(2) ALWAYS know your parameters (temperature, humidity, light cycle time), and have a killer IPM (Integrated Pest Management) system in place.
(3) Take notes. Knowing what went right, and what went wrong will help develop a better growing method.