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Autoflowering cannabis soil

Date 2nd Aug 2011   Comments 10 Comments »

Last time we found how to find the perfect pot size for autoflowering plants and now we need to see what to put in that pot.

Almost all autoflowering cannabis plants are very tough and can grow in almost any soil but how well they can grow is another question.

Most of the commercial cross-breed hybrids are very picky and can stay very short and yield very small amounts if they don’t receive adequate soil or soilless mix. When buying your soil/soilless mix you need to think about some aspects that are involved in the plants well being.

Light or heavy

First thing you need to know before buying your growing medium is – autoflower plants love to grow in “airy” growing medium. Airy means that the growing medium should be very spongy and allow the root mass to penetrate it well. If the soil is not “light” enough then the roots will struggle to penetrate the ground and that will stress the plant. Heavy soil will also stress the autoflower plant by not allowing the roots to get enough oxygen and not allowing the water to penetrate the soil, leaving some dry spots in the middle. If the growing mix is too “light” then roots won’t be able to hold, support the plant and it will easily roll over. Too light soil will also struggle to hold water and will dry up in short amount of time.

This means that you should look for a growing medium that is airy, but if you can’t get a hold of such a thing then ad some Perlite to increase the water drainage and root penetration.


Second thing that affects your plant is the nutrients that are in the soil.
Soilless mixes usually have almost no nutrients and you will need to ad them with fertilizers during the growth of the plant.

Soil in other hand will always have some amount of nutrient in it and you need to check the package to see what are they and how long can a plant live only on nutrient that are in the growing medium.  Usually commercial potting soil contains all the necessary nutrient and they are time released so that when your plant needs them they will become available. These mixes are very different and you need to check the label on each of them but in general a soil that contains these necessary elements like Nitrogen, Potassium and Phosphorus will be able to support and feed your plant for the first 3 to 5 weeks and you won’t need to feed them for these first weeks.


The third and the final thing that you need to check is the PH of the soil or soilless mix. The PH or the PH scale measures how acidic or alkaline the solution is. The PH of 7 is neutral and that means that the growing solution is not either alkaline or acidic. If the PH number is below 7 then the growing medium is acidic but if the number is above 7 then the solution is alkaline. Auto flowering cannabis plants are the same as non-auto-flowering ones and they love their growing medium to be a little acidic and the number you are looking for is somewhere between 6.2 and 6.5 but a little variation to each side won’t affect your plant that much. Usually commercial soil or soilless mixes are neutral and you don’t need to worry about this factor, but you should definitely check the label of the bag to see if there isn’t written something about a lower or higher PH. But the thing about soil/soilless mixes is that they work like a buffer and they can even out the PH levels.

On autoflowering-cannabis.com you can find more about autoflowering plants and PH scale 

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10 Responses to “Autoflowering cannabis soil”

  1. Sunny says:

    I basically learned about many of this, but never the less, I still considered it turned out beneficial. Good job!

  2. Stormy says:

    Back in school, I’m doing so much laernnig.

  3. rudedog says:

    Should I use new soil for each grow? I’m fighting with a friend and he says, Just use the same soil over and I say to use new soil.

    • midowo says:

      I usually get new soil for each grow but you could use the same one if you remove all the roots and feed your plants with chemical fertilizer.
      My opinion is that new soil will always be PH neutral but old growing medium could have salt buildups or PH problems so it is better to get new one for each grow!

  4. Daniel says:

    Been doing some research on auto-flowers and the thing that I question most is what is the absolute best medium to use from seed to harvest?

    • midowo says:

      I think that depends on the growers experience and the growing space/conditions. For some an organic mix is the best but for others a soilless mix is better.

  5. Tbone says:

    i really need help with finding a soil with the correct PH but every place i go to the soils come out to around 8 PH. can you give me a recommendation on the name of a correct soil to buy

  6. Tommythecat says:

    How much soil should we use? How many inches deep should it be for roots to have adequate space? I cant find any info on the net about this..

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