The Cannabis Grow Bible

by Greg Green

Soil Flushing

marijuana soil

A soil flush is a last resort ‘time to save our dying plant’ maneuver. You only resort to a soil flush when all else has failed. Let us pretend for a moment that you have a soil that holds a lot of water and you want to feed your plant. You take out your favorite feeding bottle and you decide that you want to add it straight to your plant and then pour water in after. This is never recommended! Always mix your food with water in a container and then use the container on your plant, such as a jug or watering can. Try follow the guidelines on the feeding bottle along with the recommendations in the book. If not the following story may happen! So you open the cap and bend it over towards the soil. You flinch, the bottle spills. The next thing you know half of your raw feeding liquid has managed to find it’s way into the soil. You curse yourself that you did not follow the instructions. You grab your hair, ‘What to do?’ you say. You pick up this book and turn to this chapter. You read about the soil flush and see that your plant now has a small chance of survival. You know that all the raw chemicals will kill your plant. All hope is lost. This is your last resort. Here is how to flush your soil.


(1) Take the plant to a sink.
(2) Turn the plant on its side making sure that you do not break the stem!
(3) If you think the stem will break then quickly find a long stick and place it in the soil.
(4) Use a piece of sowing thread to tie the plant to the stick at several points.
(5) Tape the stick to the pot.
(6) Tilt the plant on its side so that the top of the pot with the soil is facing at an angle towards the sink.
(7) Watch the colour of the liquid that runs out.
(8) Do this until all the liquid has poured through.


(1) Pull your plant back up and sit it in the sink. Pour lots of water on top of the soil.
(2) Wait until the water flows out the bottom of the pot. Look at the colour of the flow.
(3) Repeat this process until the colour of the water becomes clearer. (The soil should get very muddy when you do this and some of the mud will pass out with the water.)
(4) Once the water is clear tilt your plant on its side again and wait for all the water to drain out. You may repeat this process several times. If your feeding solution does not have acolour then you should keep an eye on the texture and smell of the solution that you are flushing out. When this changes your flush has worked.
(5) Quickly take your plant to a warm dry area and wait for the soil to dry out.
(6) Use a pH meter to test the pH of your soil.
(7) Follow step D.

marijuana soil


(1) You can use a screwdriver to make holes in your pot if it is light and the plastic is not tough. You can always use thick masking tape later to patch the holes closed. If you can do this then do and follow step B.
(2) If you can not then you need to do an emergency transplant.
(3) Quickly set up a new pot and put in new soil leaving a large gap in the middle where your plant will go in.
(4) Take your plant and use a knife to cut around the edge of the soil as close to the rim of the pot as possible. Go as deep as you can.
(5) Put you fingers in down around the inside of the rim and pull the plant out of the pot. Try not to rip the roots.
(6) Hold the soil over the sink and place it down near the drain holding it together with your hands. If your root mass is big you may need help doing this.
(7) Turn on the water and let it run slowly down over the soil.
(8) Keep holding the plant for a number of minutes until you see a change in the water that is coming out from the soil. Do not crush the soil just hold it. It will get muddy and it will break up a bit, but this is to be expected.
(9) When the water changes quickly place the plant into the new pot.
(10) Fill up the spaces with new soil and use a stick to prop up your plant if needed.
(11) Quickly take your plant to a warm dry area and wait for the soil to dry out.


(1) Every day measure the pH of the soil. If you have flushed your plant properly it should return to the near 7 mark (given that the water you use is a neutral pH of 7). In the meantime you can be reading about how to change your plant’s pH as directed below.

It is sad to say but very few plants do survive such an emergency soil flush. The soil flush is, in its essence, over-watering your plant to the point of removing most of the minerals and ingredients in the soil. If your plant manages to pull through you have done well. If your plant does not then you will know better next time. A soil flush causes the plant a great deal of shock and should only be attempted as a last resort if your plant is dying and can not be cured by any other means.

If your plant makes it, the plant may have sustained some damage. If any of the leaves are burnt or look dead you can remove them from the plant by clipping them away. Plants usually take about 2 weeks to get back to full health.

pH – bringing back to neutral from acidic:
If the pH of your soil is too acidic then you may want to bring it back to a natural 7. What you need is Lime. Lime can be bought in small containers from any grow shops. Just simply add some lime to your soil the next time you water your plant. Only add small amounts each time and then the next day use the pH meter to study the effects. What you will find is that you will get to know your soil better than I could describe here and know what it needs. Advanced growers know how much lime they need to bump their acidic soil back to 7. They know this by trial and error. This is one thing about cannabis growing. The best cannabis growers grow good cannabis because they have made many mistakes in the past. Learning is an experience and that is why people enjoy growing. They like to learn more and experience more. Don’t let a bad growing encounter put you off.

pH – bringing back to neutral from Alkaline:
If the pH of your soil is too alkaline then you may want to bring it back to a natural 7. To correct this you need to make your soil more acidic. Here is a list of ingredients that can each be used to return your plants PH to 7. Cottonseed meal, Lemon peels, Ground coffee, Some Fertilizers also are very acidic and can bring the pH down to 7.

When using this method always moderately apply the substance and check the pH. Over time you will know what measures to use. This is best left up to the grower as he/she will know how big their pot is and how much should be added. Experiment a bit and learn as you go along.

pH up / pH down:
These products are available in most grow shops. They actually act as a pH agent for adjusting your soil pH. They only come in two forms – pH up and pH down. More and more people are using these chemicals to adjust their soil pH.

Cannabis Grow Bible

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