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One of the most important aspects when it comes to growing weed indoors is the kind of soil you are using. Now, you might think that you can just dig up some dirt from your yard and pop a weed seed in there, but chances are that nothing would ever grow. There is actually a lot that goes into finding or creating the right potting soil for weed growth.
You need to think about the nutrient contents, aeration, drainage, the pH level, water retention, and more. Yes, this can make finding good soil for cannabis growth pretty darn difficult. However, we are here to help you find the best soil for growing weed indoors.
Last update on 2023-09-22 / Affiliate links / Images from Amazon Product Advertising API
First, we want to talk about all of the deciding factors and what you need to know about soil for cannabis growth, and then we have picked out 9 products that we felt deserved a mention.
Contents
4 Most Important Soil Variables For Growing Weed
Yes, cannabis is sometimes called a problem plant in some parts of the world, often being referred to as a weed due to its ability to grow in many conditions. However, there is a difference between a cannabis plant being able to survive and it thriving.
In order for the best possible results with the best yield, your pot plants need to thrive, and this means providing them with the right kind of soil. There needs to be a good balance of various variables in order for you to achieve the best cannabis growth results.
Let’s talk about the most important cannabis soil variables you need to consider right now.
1. Water Retention
One important aspect of any good potting soil is water retention. Yes, there is such a thing as overwatering and drowning your pot plants, but there is also such a thing as having them dry out.
There are lots of soils out there which have limited or no water retention abilities. This is a bad thing because it will cause the soil to dry out very quickly, and that is of course not good for your plants.
2. Drainage
Yes, we know that it sounds a bit odd to first talk about drainage for your weed soil just after having discussed water retention, but both are very important aspects that your pot plants need.
If the soil you have is way too compact and does not drain well, the water you provide the plants with is not going to sink all the way down to the bottom of the planter or container you have the plant in.
The top of the soil is going to be soaked, while the soil at the bottom will stay dry, and this is definitely not ideal for pot plants.
3. Nutrients
Another thing to consider when purchasing soil for cannabis growth is what kind if nutrients are contained within it. There is the triumvirate of nutrients or compounds which are vital to cannabis growth.
These are known as the NPK nutrients, with the N being nitrogen, the P being phosphorus, and the K being potassium. Among some others, including carbon, the NPK nutrients are vital to plant growth. (We will talk about this in a little more detail in a section further below).
4. pH
Yet another variable that you need to keep in mind when buying soil for marijuana growth is what the pH level of it is like.
The pH level refers to the alkalinity or acidity of the soil, and this is vital for healthy cannabis root growth.
If the soil you are using does not have the right pH level, or if you are not manually adjusting it, the roots of your pot plants will not develop or grow right, and they will not be able to absorb nutrients properly.
Best Soil pH For Cannabis Growth
Ok, so as we touched on above, one of the most important aspects of the soil you are going to use to grow your marijuana plants is the pH level, or in other words, the acidity of the soil. pH stands for “potential of hydrogen”. The acronym is not important per say, but the number is. The pH scale starts at 0 and goes up to 14.
Things that are very basic or alkaline in nature are going to be higher up on the scale, such as baking soda, which is a 9.5, so very basic. On the other hand, you have things like battery acid, which score a 0 on the pH scale, thus making them super acidic. In the middle, at a level of 7, which is totally neutral, so neither basic nor acidic, would be something like pure water.
Soil contains water, and therefore it has a pH level. If you did not already know, weed plants need the soil to be just slightly acidic, but not too much. Having slightly acidic soil will help to maximize root growth and the ability of the roots to absorb the nutrients required for growth and healthy development.
The ideal pH level for weed plants is a solid 6.0, so slightly acidic. Yeah, you can get away with the soil having a pH level between 5.8 and 6.3, but a 6.0 is the best.
So, when you are buying soil for your marijuana growing operation, this is something to pay attention to. There are some potting soils out there which have been adjusted for pH already, which is very useful no doubt.
If the soil has not been adjusted for pH, you will need to use a pH testing kit to monitor the pH level of the soil, and then use pH altering compounds to get the soil to the correct pH level for healthy and sustained cannabis growth (it’s important to get yourself a decent pH meter for this reason).
Coco Coir & Perlite
Something that we want to touch on is the difference between your average potting soil and substances known as coco coir and perlite. If you did not already know, both perlite and coco coir are fantastic for marijuana growth.
Coco Coir
First, coco coir is actually the husk of the coconut shell which has been broken down into fibers.
The reason it makes for a good grow medium is because it has excellent water retention, and it feels very similar to growing in normal soil too. There is also the fact that coco coir is insect neutral and environmentally friendly.
However, something to keep in mind is that coco coir is inert and contains absolutely no nutrients, which is of course not good for your pot plants. Therefore, coco coir cannot be used on its own to grow pot.
You will either need to add nutrients on the side while watering your plants, you can mix coco coir with nutrient rich potting soil, or your can buy potting soil that contains a certain amount of coco coir. At the same time, remember that coco coir is great for moisture control.
Perlite
Another substance which is often used for cannabis growth, although not on its own, is known as perlite. Perlite looks like little white rocks, but is very airy and lightweight, almost like slightly heavier popcorn.
One of the biggest benefits of perlite is that it helps to increase drainage, so you won’t drown your plants, and if you do overwater them, it will allow excess water to drain off with ease.
Its light airiness and porosity allows water to pass through it with ease, thus helping with drainage and with oxygenation too. That is right, perlite helps supply your cannabis plant’s roots with more oxygen for faster and healthier growth.
No, pot cannot grow in perlite alone. Something you might want to look for is a 50/50 perlite and coco coir mix, just to get the benefits of both substances, but you will still need to add nutrients, because just like coco coir, perlite does not contain nutrients.
If you can find potting soil that contains perlite, coco coir, and a variety of nutrients, you have found the jackpot.
The Holy Trinity Of Cannabis Nutrients – NPK & Other Nutrients
As we touched on above, your pot plants need certain nutrients in order to survive, thrive, and to provide you with the best possible results. Let’s talk about the main nutrients that you need to look for.
We will start with the NPK nutrients we touched on above, which we call the holy trinity of cannabis nutrients, nitrogen, phosphorus, and potassium.
1. Nitrogen
Nitrogen is very important for the development of the cannabis plant during the vegetative state. Nitrogen is required to produce chlorophyll in a plant, which helps it engage in photosynthesis and convert sunlight into energy for growth.
Nitrogen is also a part of the building blocks which make up the amino acids, and therefore the proteins in a marijuana plant.
2. Phosphorus
The main purpose of phosphorus in your potting soil is to allow the weed plants to produce large, healthy, and potent buds.
What phosphorus does is to allow the pot plants to suck up nutrients from the soil and process them for growth.
Cannabis plants without enough phosphorus will have inadequate root systems.
3. Potassium
Potassium actually plays a number of roles in marijuana plant growth.
Perhaps the most important function is known as osmoregulation, which helps strike the proper balance and regulation of water and salt within the plant.
It also has a number of other very important functions when it comes to cannabis growth.
4. Calcium
Calcium is also very important for marijuana plants because it keeps the cells and structure of the plant together.
Without adequate amounts of calcium, new plant growth is not going to be fast, stable, and it might not occur at all.
5. Magnesium
Magnesium is a big time building block of chlorophyll, and without it, your cannabis plants will not be able to engage in photosynthesis or store the glucose (energy), it requires for proper growth and development.
Best Soil For Growing Weed Indoors: Our Top 9 Picks
Ok, so now we are here to look for the best soil for growing weed indoors. We are going to look at a variety of products, and yes, they are going to differ a lot in terms of their properties and makeups.
We want to take a look at some really nutrient heavy potting soils here, as well as some perlite and coco coir options that are less nutrient heavy, but better for water retention and drainage. We will also be looking at some options which come with a mix of everything we just listed here.
Let’s get right to it and help you find the best potting soil for marijuana plants.
1. Miracle-GRO Potting Mix
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Here we have a great option to go with and it might just be the very best potting soil for marijuana plants out there right now. The big benefit that you get with Miracle-GRO Potting Mix is the fact that it already comes loaded with nutrients, packed to the brim.
The packaging claims that this stuff allows plants of all sorts to grow twice as big. Now, this claim might be a bit overexaggerated, but we can stay that Miracle-GRO is definitely a prime time cannabis potting soil.
It comes loaded with all of the nutrients your pot plants will need for the first couple of months at the very least. Yes, your pot plant will still need the classic NPK nutrients once all the goodies in this soil are used up, but the Miracle-GRO Potting Mix should last for quite some time before you need to start supplying your pot plants with nutrients.
This potting mix is useful for people who have a busy schedule or for beginners who might forget to feed their plants with the proper nutrients on occasion. What’s even better is that it can be used for both indoor and outdoor weed growing.
2. Fox Farm Happy Frog Potting Soil
- Ready to use right out of the bag
- PH adjusted to allow for maximum nutrient uptake
- This unique mix is alive with beneficial soil microbes and mycorrhizal fungi that dramatically expand root development
Last update on 2023-09-22 / Affiliate links / Images from Amazon Product Advertising API
When it comes to easy to use and ready to go indoor potting soil for your weed plants, Fox Farm Happy Frog Potting Soil is an all around fan favorite for pot growers everywhere.
First off, this soil is ready to use right out of the bag and does not need to be treated in any special way. What really stands out about this Fox Farm Soil is that it has already been pH adjusted. Now, as you might know, pot plants need a very specific pH level, and this soil has just that bang on.
The soil is specially designed with the right pH level for marijuana growth, so that the roots can grow really big, fast, and healthy, thus allowing your weed plants to suck up as many nutrients from the soil as possible, therefore encouraging healthy growth.
What is also really neat about Fox Farm Potting Soil is that it comes loaded with natural microbes and fungi, plus earthworm castings and hummus, which all work together to feed your plants.
In terms of the NPK nutrients which weed plants need, this potting soil has enough for at least the first month or so, before you need to start supplying nutrients from an outside source.
3. Big Rootz All Purpose Potting Soil
- Organic potting soil derived from rock phosphate, sulfate of potash, ferrous sulfate, seabird guano, langbeinite, and other essential organic material.
- Carefully formulated and pH tested for maximum results.
- Research developed award winning proprietary blend and certified organic
- Provides increased nutrients and water uptakes to foster overall plant vigor
Last update on 2023-09-22 / Affiliate links / Images from Amazon Product Advertising API
If you are growing weed indoors and starting from scratch, you need your pot plants to have a great root system, which is exactly what you will get right here with this Big Rootz All Purpose Potting Soil.
This stuff is actually designed by cannabis growers and it is made for cannabis growers. When it comes to the best organic soil mix for cannabis, this might just be it. For one, it has also been pH adjusted in order to allow for the best root health and the fastest root growth possible.
This then translates into increased nutrient uptake so your cannabis plants can suck up as many nutrients from the soil as possible. The fact that it is 100% completely organic is something that we can definitely get behind.
Moreover, some of the ingredients here include coir, seabird guano, peat, worm castings, compost, and more, in order to provide your cannabis plants with the proper nutrients they need for growth.
This particular potting soil should have enough nutrients present for the first month of growth or so. The addition of coir helps to make a lighter and air soil that features decent drainage and pretty good water retention too.
Keep in mind that this is in fact an award winning potting soil for cannabis growth, plus it can be used for both indoor and outdoor grow operations.
4. FoxFarm Ocean Forest Potting Soil
- Ocean Forest organic soil is ready to use right out of the bag
- Ideal for containerized plantings
- Contains earthworm castings, bat guano and micronutrients
- Light texture and well aerated
- Available in 1.5-Cubic feet
Last update on 2023-09-22 / Affiliate links / Images from Amazon Product Advertising API
Here we have another organic and natural potting soil that is great for indoor cannabis growth in buckets and containers. As you can probably tell due to the fact that this is the second Fox Farm product on our list today, this is a highly trusted and reputable brand name when it comes to cannabis potting soil and potting soil in general.
Something that really stands out about FoxFarm Ocean Forest Potting Soil is that it is very light and well aerated, which helps to increase drainage so your cannabis plant roots don’t drown, but it also has various ingredients present which allow for great water retention so your plants don’t dry out too fast.
FoxFarm Ocean Forest Potting Soil contains a mix of earthworm castings, bat guano, fish and crab meal, composted forest humus, sandy loam, and peat moss. These ingredients come together to form the perfect consistency which has drainage, water retention, and more.
In terms of the NPK nutrients, especially nitrogen, it has more than enough present for the first month of growth. On that same note, the pH level here has already been adjusted to between 6.3 and 6.8 in order to allow for maximum nutrient uptake and healthy root growth.
5. Super Soil Organic Concentrate
- Concentrated Strength Organic Super Soil (just add soil media)
- 5 pounds of concentrate mixed with potting soil amends 25 gallons of containers
- Just water from seed to harvest (microorganisms in the super soil provide nutrients to the roots over time)
- Living Soil technology for your vegetable garden
- Growing does not need to be difficult to get great yields and quality
Last update on 2023-09-22 / Affiliate links / Images from Amazon Product Advertising API
When it comes to cannabis potting soil that is loaded to the brim with nutrients, the right nutrients, which your marijuana plants need to grow and flourish, Super Soil Organic Concentrate is undoubtedly one of the best options on the market right now.
Technically speaking, you should never have to provide your cannabis plants with any nutrients whatsoever when using this soil, at least not until well into the flowering stage. The fact of the matter is that Super Soil Organic Concentrate is so strong and full of nutrients and fertilizers, that you cannot use it on its own.
You will have to choose one of the potting soil mixes listed above to mix with this particular option. Using only Super Soil Organic Concentrate may actually cause nutrient burn in your plants, especially young seedlings.
The packaging claims that you only ever need to water your plants and never provide them with nutrients, which is technically true if you transplant your marijuana plants at least 3 times, and use a good amount of this organic concentrate each time.
Keep in mind that this is technically not potting soil, but a potting soil organic additive, kind of like soil that is loaded with nutrients and fertilizers. Do remember that this stuff is specially designed for indoor cannabis growth.
6. Fox Farm FX14100 Coco Loco Potting Mix
- Coco Loco Potting Mix has the ability to hold more than its weight in water while still draining well
- The coir in Coco Loco behaves like little sponges offering nutrients and water as needed by the plants
- Lower humidity reduces the possibility of attracting mold and root rot, as well as leaving insects less likely to bother your potted plants
Last update on 2023-09-22 / Affiliate links / Images from Amazon Product Advertising API
Yes, here we have yet another option from Fox Farm, and it is because this is a big time brand name in the cannabis growth world. Here, you get potting mix that is made out of coco coir, which is a fantastic way to go when growing cannabis.
Now, what you need to know here is that this stuff does not have too many nutrients inside of it, which makes it great for seedlings and small plants that can easily suffer from nutrient burns.
If necessary, you may need to add some extra nutrients and fertilizers over time, or just mix this stuff with other potting soil that is a bit more nutrient heavy.
The advantage to using this Fox Farm FX14100 Coco Loco Potting Mix is that coco coir has excellent drainage abilities, it is quite air, yet it can hold a heck of a lot of moisture too, all things which you need for your pot plants.
The coir here is like a little sponge which your cannabis roots use to grow big and strong. What’s also nice about this option is that it goes a long way in controlling humidity, and reducing mold and fungus too.
It’s a great option to go with if you live in a really humid environment and are afraid of root rot occurring or insects being attracted to overly humid conditions.
7. Mother Earth Coco Plus Perlite Mix
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This is another great option to go with if you need good aeration, airiness, drainage, and water retention. Now, this is a coco coir and perlite potting mix, so not exactly potting soil, but most would say just as good, if not better than your average potting soil.
Just like the option reviewed above, Mother Earth Coco Plus Perlite Mix does not really contain any nutrients per say, such as the vital NPK nutrients, which means that you will have to add nutrient supplements when watering.
You could also mix this Mother Earth Coco Plus Perlite Mix with nutrient rich potting soil to create your own soil mix for the best results. The great part about this stuff is that it comes loaded with 70% coco pith and fiber, plus 30% perlite.
Together these two compounds work to provide your pot plants with excellent drainage as well as water retention at the same time. It’s also a good option to go with if you live in a really humid environment because Mother Earth Coco Plus Perlite Mix helps to prevent root rot, it combats overwatering, and it tends to not attract pests and insects.
It’s not something we would usually use on its own, but it is a good option for creating your own soil mix.
8. Roots Organics Rod Original Potting Soil
- Roots Organics Original is a ready to use mix created with a balanced air to water ratio of porosity and water retention to allow for frequent feeding of fast growing, heavy feeding plants.
- For exceptional results, feed with high quality nutrients, such as the Roots Organics fertilizer line.
- Our Roots Organics soil bags double as pots – just cut the top off, drop the plant in, and you’re ready to go.
- Ingredients: Perlite, Coco Fiber, Peat Moss, Composted Forest Material, Pumice, Worm Castings, Bat Guano, Soybean Meal, Alfalfa Meal, Fishbone Meal, Kelp Meal, and Greensand.
- Also contains beneficial mycorrhizal fungi: Funneliformis mosseae, Rhizophagus intraradices, Septoglomus desertícola to enhance uptake of plant nutrients, increase root biomass, and help container grown plants resist stress
Last update on 2023-09-22 / Affiliate links / Images from Amazon Product Advertising API
Here we are going back in the other direction, and it might just be some of the best organic soil for cannabis growth out on the market right now.
We say that we are going in the other direction because the last couple products we looked at were all about coco coir and perlite, which is not the case here. Now, this is a coco fiber based potting soil, but what is important to note here is that this stuff is loaded to the brim with nutrients, both the NPK nutrients and others.
In fact, this stuff is so nutrient heavy that it is too strong for seedlings and will probably kill them due to nutrient burn. With that being said, Roots Organics Rod Original Potting Soil is the perfect option to go with for slightly larger plants that are well into their vegetative or flowering stages.
In fact, this is a perfect option to mix with either product #6 or #7 from above. That said, Roots Organics Rod Original Potting Soil does already come with a certain amount of pumice and perlite included in it, which helps to increase aeration and drainage, with the addition of coco fibers allowing for maximum water retention.
There is also the fact that is 100% organic. Now, you might be potting in containers, but technically speaking, this stuff comes in a bag that doubles as a container, planter, bucket, or whatever else you might normally use for cannabis growth.
9. Espoma SS8 8-Quart Organic Seed Starter
- CONTAINS: This organic Seed Stating soil mix is a rich blend of sphagnum peat moss & perlite with yucca extract and lime to ensure correct pH.
- MYCO-TONE: A blend of endo & ecto mycorrhizae.
- WHEN TO USE: Use to germinate and start seeds. Great for flower, vegetable, herb & more plant types. Can also be used to root stem and leaf cuttings.
- PROMOTE ROOT GROWTH: Organic seed starter mix ensures ideal moisture retention and aeration.
- ORGANIC GARDENING: Contains a rich blend of only the finest natural ingredients. No synthetic plant foods or chemicals are used.
Last update on 2023-09-22 / Affiliate links / Images from Amazon Product Advertising API
Up until now, most of the options which we have looked at here today were more than ideal for cannabis plants in their vegetative and flowering states.
However, a lot of them were a bit nutrient heavy for seedlings, although usually not to the point of causing seedling death. Yet, none of the options were 100% designed for cannabis seedling growth, well, not until this here Espoma SS8 8-Quart Organic Seed Starter mix.
As you can probably tell by the name of it, this stuff is indeed specially designed for marijuana seedlings and the earliest growth stage of your marijuana plants.
Now, it does contain a little bit of nutrients, small quantities of the most essential ones, just to ensure that your pot plant seedlings to get the ideal amount of nutrients, but it is not overloaded to the point where it will cause nutrient burn.
Espoma SS8 8-Quart Organic Seed Starter is all about promoting healthy root growth, creating a strong root system, and allowing your pot plant to efficiently absorb nutrients, especially as it starts to grow larger.
It comes with a mix of peat moss, peat humus, perlite, and more, for strong roots, good water retention, and a bit of drainage too.
Soil For Cannabis Growth – FAQ
Let’s quickly go over some frequently asked questions in regards to the best soil for indoor marijuana growth.
1. What Is The Proper pH Level For Marijuana Growth?
Cannabis plants require the soil to have a pH level of 6.0, so slightly acidic, but this can be pushed down to 5.8 or up to 6.3, but 6.0 is the ideal pH level.
2. What Does NPK Stand For?
NPK is an acronym for nitrogen, phosphorus, and potassium, the 3 most important nutrients for marijuana plant growth.
3. How Do I Increase Soil Drainage & Why Is This Important?
The best way to ensure that your cannabis growing soil features proper drainage is to use soil that contains perlite. This is important so you do not overwater or drown your cannabis plants.
4. Why Is Water Retention Important For Cannabis Plants & How Do I Increase It?
Water retention is very important so your plants (and the soil) do not dry out too quick, and so they get a steady flow of water and nutrients. One of the best things to use for water retention is coco coir.
5. What Is The Best Soil To Grow Medical Marijuana?
To grow medical marijuana indoors, or any other kind of marijuana, the soil needs to have a few important features included good drainage, aeration, water retention, the right pH level, and the proper NPK nutrients, as well as other nutrients.
One of the potting soils we have reviewed above should do fine here. One that contains a mix of soil, nutrients, perlite, coco coir, and various other ingredients will suffice.
Other Related Articles You Might Like
You might also like;
- Our guide on what equipment you need to grow indoors: You can check it out here.
- The ideal temperature and humidity for growing: read our guide here.
- A full breakdown of how much it costs to grow weed: check it out here.
- A buyers guide on grow bags, see our guide here.
Conclusion
We hope that we were of assistance on your journey to finding the right soil. Before you go out and buy soil, remember to think about the nutrient content of it, drainage, aeration, water retention, the pH level and more.
You don’t want to buy the wrong or inadequate soil for your cannabis plants, or else they won’t grow right and you will be severely disappointed with the results.
When it comes to the best soil for growing marijuana, we would definitely recommend one or multiple of the options we have recommended above. A good mix of soil, peat, nutrients, perlite, and coco coir is absolutely a great start.
