Mar 242011
 March 24, 2011

What Is The Best Soil For Growing Cannabis?

Marijuana growers need to make many different decisions when they are planning out how to grow their plants. Besides deciding whether to grow indoors or outdoors, indoor growers need to choose whether to use soil or a hydroponics system for their indoor setup. In case you haven’t used hydroponics before and are willing to dedicate the money to it, it can be a very practical option to choose.

Generally speaking, newer growers decide to grow their plants in soil at first. Taking this step allows them to get a feel for the undertaking of growing marijuana plants without risking huge amounts of money and extra time spent researching. Either route can be useful, but in this article we will cover information for people who want to grow their marijuana plants in a soil-based system.

Growing marijuana in soil

marijuana soilMarijuana roots extend deeply into the soil as they hunt for the best sources of water and nutrients. This is why indoor growing requires a different technique that will compensate for this lack of space. To put it simply, the root systems of indoor marijuana plants need to be smaller. The water and nutrients come from the grower rather than natural sources in wild soil, so root systems should be able to thrive without extending out too far.

The main thing you need to worry about with root systems is that the temperature stays relatively warm – around 68 degrees Fahrenheit. You will also want to check that there is plenty of water and oxygen throughout the soil. Make sure to download my free marijuana grow bible at this link here for more growing tips.

marijuana soilPros and cons of soil growing

Irrigation is more easily done in soil because mistakes are more easily made with hydroponic systems. Fertilization is also simpler, if only because people have been growing plants in soil for thousands of years, meaning there is tons of information and advice out there. Soil types can make a big difference in the taste of the resulting marijuana, which is an added bonus.

Soil isn’t perfect, however. It requires lots of space and weighs a lot, making things rather difficult for people growing indoors. Pests and insects are more likely to be found in soil as well, not to mention the fact that some people simply don’t have the “feel” required for growing any plants in soil. Read the article ‘How To Grow Marijuana Hydroponically‘ if you don’t want to grow in soil.

marijuana soilMarijuana soil container size

The size of your plants’ containers will alter the size of your plant’s root system. If the roots have more space, they will fill out their space even more quickly – making growth easier. Problems occur when the plant outgrows its container.

Regular sized marijuana seedlings will do well in a container that is 10x10x10 centimeters until it reaches the height of between 25 and 35 centimeters. At that point, you will need to transplant it to a container that is two times the size of the first one (15x15x20 centimeters). When the plant surpasses the 80-centimeter mark, you will need to transplant it to a container that holds 10-12 liters. The container size keeps increasing as the plant exceeds the 1-meter mark, and so on.

marijuana soilMarijuana soil nutrients

Soil already has lots of nutrients naturally, since it is made up of organic materials. Materials like rotting vegetables and animal manure cannot be placed directly on your plants as fertilizers – they need to be broken down additionally before they are able to be absorbed by the plants’ roots. Worms and insects are useful “tools” when breaking down these materials, as is rain. Water dissolves these and other materials allowing them to be absorbed by the marijuana roots.

While these things happen easily and naturally in the wild, it is not so in indoor growing systems. That is why beginning with soil that is rich in nutrients (as well as sterilizing it before planting) is so important for indoor growers. The best way to sterilize soil is to use heat, which is not 100% effective but will help ensure the safety of your plants nonetheless.

Download my free marijuana grow bible and learn how to increase nutrient absorption

Nutrient-rich potting soil mix can be found at your local garden center, and it can also be made on your own. Oxygen, a lukewarm environment (approximately 20 degrees Celsius), plenty of water, a balanced pH value, and lots of nutrients will create an environment that encourages healthy growth in any marijuana plants.

As an indoor grower, you will have to be especially aware of what your soil needs to contain. The pH value, humidity, and nutrients will make a bigger difference than you might expect, so keep tabs on these things. Additionally, if your soil doesn’t retain water well, plants won’t have time to “drink” as much as they need to. Too much water retention, however, can encourage fungal growth, which would lead to devastating root damage. Use vermiculite, sphagnum moss, turf, or perlite to alter the retention of your soil.

marijuana soilMake marijuana soil yourself

Soil is pretty easy to mix, as long as you pay attention to the ratios. These ratios also will change according to which stage of life your marijuana plants are in. Early stages of life, for instance, require balanced amounts of turf, perlite, and worm meal. Vegetative and flowering stages need balanced amounts of turf, worm meal, and compost instead.

To decrease a too-high level of compost, simply add chalk. You can also use liquid fertilizers as a way to add nutrients to your soil, and they can be made yourself. Just be sure that the liquid is homogenous and has equally balanced nutrients, thus preventing it from “burning” your plants. For nervous beginners, a store-bought option is probably your safest choice.

Watering marijuana soil

Watering in soil can be difficult because it varies according to the soil type and environment. Hot environments need more water while cool environments require less. Water works to move necessary nutrients and minerals to the roots, where they are then transported to the rest of the plant. Water also works to cool down plants when they are too warm and to keep the structure in line. Perhaps most important of all, water is a necessary ingredient for the process of photosynthesis to successfully be carried out. As a general rule of thumb, simply water until the soil is moist but not wet to the touch, unless you want fungi to grow and harm your marijuana plant’s roots.

If you want to start growing, download my free grow guide and order some marijuana seeds. All top quality marijuana seeds are available in my marijuana seed shop. We ship seeds to the US, CA and many other countries. For any growing related question please visit the marijuana support page.

heliospectra led marijuana grow light

About Robert Bergman

Robert Bergman is a master marijuana grower. Robert Bergman is the author of 'Marijuana Plant Care' and 'The Marijuana Grow Bible'.
Dissenting opinions are welcome, insults and personal attacks are discouraged and hate speech will not be tolerated. Spammers and people trying to buy or sell cannabis or any drugs will be banned. Read our comment policy and FAQ for more information

    ^Can’t U Juhz Grow Reggie Wit Juz Soil??

  • Billybaggz

    I found a round egg on the top of my soil then I squeezed it and it popped like a lil ball or something…what is it and should I be worried

  • The Real Grower

    Just use Scotts Miracle Grow Soil. It feeds for 3 to 6 months and no need to check the ph level since its already good dirt.

    You might kill a plant giving it that much food.

    You don’t want to kill your tomato plants.

  • Shane Wyatt

    So what about using fine sand for after the germination but before the bigger pot transfer? Do you think this will help retain the initial moisture and guides the root to dig deep for the soil?

  • james

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    • johhny1

      purple k from Oaksterdam? or seed ?

      curious in the 818

  • b real

    i am a new grower i just bought 6 seeds 2 purple widow 2 thc bomb and 2 white skunk wat is the best soil and food to use to get the best out of my crop

    • adamC

      wasgood i got my canabus card u got fire

  • johhny1

    COMPOST! worms

    The best soil is only 1 part of the equation. How fast the soil drys , how much nutrients to give .
    Jorge Cervantes has some good books ,websites ,youtube.

    Another good source is “bio-dynamics” Stieners belief that herbs and weeds removed by man actually regulate molds ,diseases. re-introducing these organic plants or applying to garden compost helps plants thrive in an organic environment

    SubCool has some great vids on youtube and I have only heard good things on his Vids

    back in the day , we had to hide this, We parked our cars miles away from the hydro shop ,paid cash ,told no-one.
    Now information flows freely on the Net
    To all Newbies the best advice I have heard was “whatever keeps it green”

  • Bronx Bull

    This thread is huge good comments….what type of supplement(s) will I need to add to this after I plant?

  • Adam

    Is that the exact amount to mix for every ingredient

  • cajyen

    Ok Hello Ppl I Have Read Most Of Your Articles And I Am MoRe Lost Then When I Started Im Trying For My First Time To Grow I Have The Soil That Was Recommended To Me The Lights And The Seeds. I Was Told To Put Coffee grounds In The soil Should I Or Not Do So And If Done RightHow Long Would It Be Until I See Some Kind Of Results.

  • conky

    can I leave my soil testers in the pot during the entire grow?

  • long haul drifter

    im growing autos and wondering can I start them under cfls and then transfer them to the hps after a couple weeks of grow?

    • Spinnr

      Yes you can and prob. the best way to start them off.

  • sandiw

    I’m confused now, but I read online that you can use soil for tomatoes and watermelon and it works good. Should I do this?

  • FEDupWITHstupidity

    2-4 people can easily mix large quantities by laying it all on a drop cloth or heavy plastic square shaped tarp. Have each person stand on one of the sides of the tarp. Each person grabs on and one at a time take turns lifting their side high enough to push the dirt to the center and beyond if possible. This is easy and there is no need to jump in and get dirty. You can use your legs to help with pushing your side to the middle. After 5 minutes of mixing, it is thoroughly combined

  • aliensRdrones

    I have been testing different methods for desert growers add 5 2 cubic ft bags of Lowes top soil , add one half bag chicken manure, one quarter bag steer, 2 bags hydroponics mulch, 2 1.5 bags hydroponic house plant soild, add coco shell 5lbs, 1lb sea kelp,5lbs peat moss and 3 lbs pearlite add 10lb natural pea gravel the smaller the better and 2lbs clean washed sand add add 1 bag 1.5 cft cactus soil mix well add I bottle peroxide large mix very well add to plant pots plant need bamboo reed building with clear roof we use a small swamp cooler to keep temp down adding humidity set on low away from plants pointing inward flowing out through reeds fantastic setup if done righ

  • Nezzie Spinney

    First time grower started with my seeds in
    Im just wondering what do i do next ? Its been like this for two weeks ? Need help

  • Nezzie Spinney

    What do i do next ?

    • KR

      Let them all grow and then wack the ,ail when it.identifies itself. Then growth the two females in a way where pruning properly will allow them light, strengthening ability, and give you sticky high yields. IMHO.

  • Nezzie Spinney

    First time grower started with my seeds in
    Im just wondering what do i do next ? Its been like this for two weeks ? Need help

    • Matao

      Give more them more light. Make sure your light cycle is proper. Keep growing. Soon move to the veg stage. Look on YouTube how to grow weed indoors you will get many results.

      • Nezzie Spinney

        Hey man they getting roughly 12/12 light n dark , but just the sun when will more leaves come , i just transplanted them from a small jiffy hot house to the big pots just wanted to know if they will grow the soil i started them from seed was on my pic and i bought today the premium potting mix today when should i transder them again or should i just leave them in the soil as is ,??? I need help pls ???

    • Jay Millz

      What the fuck? If you’re going to depend on the sunlight from outside to give them light then plant them outside for god sake. You need to buy some lights if you want to grow them indoors or otherwise you’re going to end up with dead plants. Also your light schedule should be 18h on and 6h off.

    • Nick

      I would reccomend germinating your seeds in a glass of water for only 24 hours or until the seed splits and you are able to see the taproot. Germinating in soil takes much longer and can be much more tedious.

  • Dave

    You said ”I will use this mix for a full year just adding like 30-50% in the lower
    potion of the container and plain base soil in the top portion.” Do you reuse the soil after the plant is done or you use the left over mixed soil in the trash can for a year?

    How much Mycorrhizae do you add?

  • need4weed

    first timer. useing 1 part vermiculite 3 parts perlite 3 parts topsoil 1 part mushroom soil , they are all organic. will this be ok or am he f@#@! it up?

  • lovesthebud420

    im a first time grower and want the most successful bud i can get, were you say “Here are the amounts we have found that produce the best tasting buds and strongest medicines” underneath that were you have a list of things to add to the base soil does that show how much to add to one bag or eight?

    • Will Riggert


  • dee ramos

    Im a first time grower i havent planted my seeds yet bcuz i dnt know what soil to use :o please help i need a just water method soil that will last the whole plants life time nothing complicated
    contact me to my email so i can ask you some questions

  • pato banton

    what is the best water for outdoor growing using this mix? if i grow near a river could i use that water?

    • Ronald Hams


    • tman

      always check the ph level of river water. our river is a 7ph most of the time. during the fall when the trees are dropping leaves it can become acidic. always check ph. it will still be better than city water.

  • Dirt Head

    It says you use 7 gallon containers and “just add water”. What would I have to do to make “just add water” work for 20 gallon containers?

    • steve3231

      Multiple x3

  • karla

    What if the person is a beginner, & is just trying to do 3 plants

  • Ann E.

    my daughters father-in-law has a friend that has a legal grow and he gave Mike all his soil from last years grow. My daughter used some of it to fill her newest flower garden as did Mike and we all thought that we would have a great growing season except that the soil has been killing everything. Anyone know why?

    • GuerillaSG

      Looks lile the soil has burnt the plants. What you should look for is the NPK of the fert that has been added to the used soil*. Different plants have different needs, one soil mix does not accomodate to all plants.

      *I just assume it is used with ferts already in it.

  • WatchingAngels

    I realize this thread may be inactive, but if there is still someone on the other end, I have 2 questions – one about scaling and the other about procedure.

    1) Do you end up using all 8 bags of base mix? Meaning that if someone wanted to make smaller batches, they could divide all other ingredient quantities listed by 8 to obtain a per-bag recipe.

    2) Is the 30 day ‘cook’ period mandatory? Can it be reduced within an acceptable range?


  • Tom Stroh

    The best advice I can give is to watch the YouTube video “Grow Like a Pro” put out by High Times a few years ago…….

  • Karthick Ram

    i’m planting cannabis, single plant in a pot. for past 20 days i think.. daily i am pouring some water.. in day time i keep in outdoor and in night i keep it in a box with cfl bulb, box is fully closed with some holes.
    give me some tips and steps to grow better.. and my steps are correct?

  • Tanvir hasan

    All of 12 soil textural classes loam soil is the best for most of the plants cultivation. Because loamy is the intermediate mixture of sand, silt and clay. In loamy soil the three major components of soil remain in suitable amount for plants well growth.