Marijuana Soil & Medium
The medium is where your marijuana plant will do its growing. Regardless of whether you are growing in soil, hydroponics or a soilless mix, any good marijuana growing medium will have good water retention and be able to keep the roots of your plant supplied with oxygen.
This section will take you through the basics of what you need to look for in good mediums for both soil and hydroponics, as well as supply a list of mediums and their properties.
As a growing medium, soil is the easiest, fastest and cheapest way to get started, but choosing the best soil for weed is an important job. It is also more manageable and forgiving than other mediums, making it perfect for the beginner grower. Many growers would argue you get the best tasting bud from a soil medium, however, soil grown plants tend to take longer and need transplanting into bigger containers once they have started which can put the plant under stress and stunt its growth.
When choosing the best soil for weed, there are a couple of things to take into consideration; the pH and the texture. Marijuana grows best in soil that is pH 6.5 to 7, allowing nutrients to be used efficiently. To check the texture, pick up a handful of moist, but not sodden soil. The texture of the soil should barely stay together when run through your hand, and feel spongy when you clench your fist. The best soil for weed will hold water, but have good drainage.
There are a number of good soil mixes available for you to buy that aren’t expensive and on the whole, shop bought mixes contain most of the nutrients needed in a marijuana growing medium. A good marijuana soil mix, like Fox Farms will need very little amending. If it is out of your price range, you can use an all-purpose soil from Wal-Mart and use the guide below to make any amendments you might need to make your medium suitable for your marijuana plant(s).
Can I use garden soil to grow marijuana?
You can use garden soil to grow marijuana, but it is highly likely that you’ll need to mix it with compost or make amendments to include all the nutrients the plant needs. Make sure you check the pH using litmus paper or a pH meter as well as the texture to see if it is suitable using the method described above.
To increase water retention to your marijuana soil add vermiculate, or increase drainage by adding perlite. If your soil is too acidic, mix in dolomite lime using 1 cup for every ¼ litre of soil to bring pH back in line. To make the soil more acidic, add coffee grounds or citrus peelings. Remember: always mix amendments into your soil when it is dry.
What can I add to my marijuana soil?
Whether you are growing organically or not, there are many products available that will help your soil have the correct texture and nutrients for a healthy marijuana grow. Below is a list of the most commonly available in the market.
Perlite – Perlite is heat expanded glass or volcanic rock and is great for water and nutrient retention as well as aiding drainage in planting mediums. It is pH neutral, so can be added to any soil. Be careful when mixing as the fine dust from Perlite can get in and damage your lungs, so wear a mask when mixing.
Vermiculate – Vermiculate is crushed volcanic rock and is great for holding nutrients and water. Vermiculate gives fine and fast draining soils body, increasing their water retention. Its pH ranges from 6 – 9.5, so will need to be checked before being added to any marijuana soil. It can retain too much water so only use with fast draining soils.
Dolomite Lime – Dolomite lime is used to increase the pH of acidic soils. As its pH is only slightly above neutral, it stabilizes the pH safely.
Guano – Guano is dried bat or bird excrement and is available as both high Nitrogen and high Phosphorous formulas. Too much Guano will burn the roots of your plants, so follow the manufacturer’s instructions.
Worm Castings – Worm castings or worm excrement are an excellent source of micronutrients and also a good supplementary source of Nitrogen that will not burn your plants. Be cautious when adding worm casting as they are heavy and restrict root growth.
Kelp Meal – Kelp Meal is dried and ground seaweed and is full of potassium. It helps with nitrogen delivery and helps resistance to disease.
Bone Meal – Bone meal is ground up bones from the slaughterhouse and is high in phosphorous. Its neutral pH and lime content offer a buffer against acidic soil. However, it can attract pests to your grow.
Coco Peat/Coir – Coco peat is made from the hair that surrounds the husk of a coconut. It is a good retainer of moisture while still draining well and is durable, rot resistant and inexpensive. It retains a good structure and has pH of 5.5 to 6.8 meaning that it can be used on its own or mixed 50/50 with soil.
There are a number of soilless mixes available for marijuana growing. Like soil, they should have a pH between 6 and 7, and a coarse but spongy texture. Many soilless mixes come without nutrients unless stated on the bag. This can be an advantage as it enables you to have greater control over the fertilization of your plants. There are many premade soilless mixes available for you to buy, you can purchase soilless components separately, and mix them yourself to create the consistency you want, mixing when the medium is dry. Below are two common soilless mixes to get you started;
40% Worm Castings
Weed grown in a hydroponic set up will grow faster than in marijuana soil, however, hydroponics are less forgiving making them more difficult to use. Unlike soil, the mediums used in hydroponics will not buffer the plant from any grower mistakes or acts of God (i.e power outages, no water supply, etc) and is there purely for root support.
When choosing a medium to use for hydroponics your decision should be based on which system you’re using. Another important consideration is whether the medium is able to hold water, but drains really well, so that it copes with constant watering. Below is a list of mediums to be used in your hydroponic system:
Rockwool – Rockwool is literally spun rock and is probably the best all round choice as a hydroponic medium. It is impossible to over water but still holds ten times the amount of water soil does, while supplying the roots with a good amount of oxygen. Rockwool needs soaking for 24hours as it has a high pH. It has no buffering capacity, so users must exercise caution when administering nutrients.
Expanded Clay Pellets (Hydroton) – Expanded clay pellets have been heated until they have expanded, leaving them with internal pockets that hold nutrients and oxygen, while still having exceptional draining capabilities. They are pH neutral and an excellent choice to be added to mediums that need extra drainage capacity.
Coco Peat/Coir – Coco peat or Coco coir is fast becoming one of the most popular mediums used within hydroponic marijuana growing. It has a the perfect pH for hydroponics at 5.5 to 6.8, has good moisture retention while draining well, and offers some of the buffering capability of soil. It can also be used across a wide rage of hydroponic systems.
Perlite – Perlite drains fast, has a neutral pH and courser types can be used in hydroponic grows. However, it has a tendancy to float and the dust particles will clog the pumps of circulating systems over time. Like Rockwool, Perlite also offers the roots no protection from nutrient solutions and is best used in conjunction with another medium.
Vermiculate – Vermiculate holds a lot of water and is best when used in conjunction with perlite. It also has excellent buffering abilities. However, the pH of vermiculate ranges from 6-9.5, so it will need adjusting before using. It also contains trace elements of magnesium (Mg) and phosphorous (P) so needs to be flushed before use.
19 comments on Marijuana Soil & Medium
i am growing a plant for the first time,in a pot on window sill.it is now 10 inches high. do i pinch the growth in between the stem and the leaves,like you do on tomatoe plants?
Alan sputnik – roots do need oxygen – plants take in small amounts of oxygen through their roots and beside that there needs to be good aeration to allow CO2 to diffuse into to atmosphere to avoid CO2 toxicity please don’t talk about what you don’t understand especially when it can impact other people.
Yes, roots need oxygen. This is why you get an unhealthy plant if you let it sit in water (in a tray or pan) or if you have very poor draining soil. It is obnoxious to write a comment like that when you don’t understand. You wondered why nobody else commented on your find? That’s because you were wrong…
Yo so I know I can add stuff to my soul to give the weed certain traits and I mean certain things like fish guts or orange peelings, those are the only two things i know thoe so can anyone tel me other things I can put in my soil for dank trees
believe me,we thought we knew the game, probiotics is teaching us that these plants have been showing us little of there potential.
Roots need oxygen? Um, I don’t think so. Interesting how nobody’s paying any attention here. Hah, must be the dope. Sure, most of the advice on how to grow is good, but these people obviously don’t know what they’re talking about…
can you use miracle grow soil for weed
I too am a beginner and growing one plant. It’s doing very well so far. I have it in a somewhat small pot but needs to be transplanted. I’m pretty sure it’s a female. I put it outside in the sun during the day and bring it indoors in the evening and place it on a heating pad under a portable fluorescent lamp light until it gets the 18 hours needed.
I have it sitting on top of my clothes dryer because I have no where else to put it. I don’t want to spend money on greenhouse kits and I usually don’t have company over But I don’t know what to do IF it grows bigger. it’s time, I think, to transplant it into a bigger pot and was wondering IF the same lighting and heating pad will be enough for it to grow until maturity? I read that humidity, ventilation, etc. is important but I don’t have humidity in my home nor use a fan etc…Will this one plant grow and succeed? The only type of water I use is filtered and at room temperature. I haven’t used any “plant food” on it yet and was wondering if I should? Also, I have a cat, when or if my plant grows bigger and place it on the floor, will it be safe from my kitty? If she decides to eat it, smell it or rub up against it will she and the plant be ok?
Please excuse my ignorance but as i’ve said I’ve never grown pot before. Did I forget to mention that it’s illegal here in TN? I could use all the help I can get!!
Thank you so very much for sharing your vast knowledge on your website, it’s very helpful and insightful!!
Any suggestions and advice would be greatly appreciated,
This is my second time at bat. I had two strokes so I grow both male and female plants.(not in same room) My question is about the roots. When I dumped the 5 gallon pales I noticed that almost the whole thing was roots. So is the pale to small or is that just how they grow?
How spread out do my seeds need to be?
Hi there once they are germinated and ready to move to the medium which is clay pellets it scares me to move them there because th pellets dont seem as though they would support it my question, move to clay pelletts right from germination?
Hey now, what is the best combination of soil for growing marijuana? Soil and Fertilizer exactly what they should be combined.
hello there, I’ve grown buds before and I got a question? 1in in a week an 1/2? is that good or that bad? And I gotta tell you this, you see I had a plant growing pretty an tall then one day my sister’s sheep came and eat it. I was hella mad, kicking up dust and wanting to slaughter that sheep. Eventually I forgave that sheep and said my good byes. I needed to take a piss and guess what I piss on the stem of that eaten plant. I came back down from mountain to check on it and what do you know? It grew back like crazy!! it grew back like a pitch fork.
HI Michael, I am not a pro but I suggest if u only have room for one plant I would start by ordering female auto flower seeds. you can order single seeds online. the autos don’t grow as large and also saves on the process of sexing. the negative is much less yield. I grow medical weed for my seizures, for your arthritis I would try weed with a high CBD level. happy growing, I wish you well. ~clarkman.
Either option is possible however we would suggest germinating using the paper towel method before planting in your medium.
Could someone tell me if I need to germinate my seed using the paper towel method or would it be ok to just plant the seed in my grow medium? That is my biggest confusion right now. If I do have to germinate the seed using a paper towel, is it ok to plant it directly into the medium? Thanks…
Hello there I am just growing for myself. I am only growing one plant it is my first time and I haven’t a clue if it will grow or not. I have arthritis and a bad case of it. I am on Morphine pills and they don’t do jack for the pain. I started growing the plant four weeks ago and it is about three inches tall. I already transplanted it one time. It was about three inches tall and had a thin stem so I out in down in the soil about two inches with fresh soil. I am using orchid soil mixture,it is the consistency that I read about spongy and yet hods the water just right. I have to grow it in on the window ledge in my apt I don’t have any other space to grow it. It gets sun form sun up to sun down and seems to being doing ok. Could you give me some grow tips on how to do this and if I am growing it ok so far. Like I said a I have never done this before and I would like for this to turn out. I have no clue what type of seed this is
Hi Michael, three inches in 4 weeks isn’t a lot. From what you’ve written it sounds like your plant isn’t getting enough light. How many hours of direct sunlight is the plant receiving? That would be first thing you need to look at. What strain are you growing?
Hello there I am just growing for myself. I am only growing one plant it is my first time and I haven’t a clue if it will grow or not. I have arthritis and a bad case of it. I am on Morphine pills and they don’t do jack for the pain. I started growing the plant four weeks ago and it is about three inches tall. I already transplanted it one time. It was about three inches tall and had a thin stem so I out in down in the soil about two inches with fresh soil. I am using orchid soil mixture,it is the consistency that I read about spongy and yet hods the water just right. I have to grow it in on the window ledge in my apt I don’t have any other space to grow it. It gets sun form sun up to sun down and seems to being doing ok. Could you give me some grow tips on how to do this and if I am growing it ok so far. Like I said a I have never done this before and I would like for this to turn out. I have no clue what type of seed this is.
Thank you for your time and assistance. Any information that you can give me would be helpful.