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Best soil for autoflower cannabis seeds

Soil Mix Made to Grow Great Autoflowers

Everyone is getting on board the growing your own weed train, and it’s a good thing. Learning to grow your own cannabis is a valuable skill for any cannabis lover. Now, with so many states legalizing the home growing of marijuana, more people are discovering their green thumbs.

One of the most common mistakes among newer growers is growing their cannabis in the wrong soil. A lot of times, this comes from using the typical soil that you can find at a hardware store. For instance, MiracleGro is terrible for cannabis plants and will more than likely end up killing your crop. The fact is, cannabis is only as good as the medium it was grown in. If you want to grow top-shelf cannabis, you need to use top-shelf soil.

Soil Mix Made to Grow Great Autoflowers

The Importance of Good Soil for Autoflowers

One of the biggest mistakes a novice grower can make is growing their cannabis in the wrong type of soil. Even experienced growers can make this mistake. If you’ve been growing vegetables for years, you already know how to grow plants, right? You are correct, of course, but marijuana, although a hardy plant, still has specific needs that cannot be met by many of the commercial soils that you’ll find at the local hardware store.

It is no surprise that many experienced growers that are new to growing marijuana may be tempted to use MiracleGro. It is a very well-known brand of plant food and soil, and it’s used in gardens throughout the country. It has made our flowers bloom brighter and our tomatoes juicier, does logic not dictate that we should use it on weed too? As it turns out, using MiracleGro is perhaps the worst thing that you can do as a cannabis grower. The main issue with this soil is that it only contains one type of formula. As you know, cannabis goes through several different stages , requiring a variety of nutrient combinations. As a result, your plants become nutrient deficient, get sick, and then die. While autoflowers can handle things that would kill photoperiod plants, even they cannot handle the amount of nitrogen contained in MiracleGro soil.

So now that it is clear why Miracle Grow is a bad idea let’s talk about what you could gain by using the correct soil. First of all, you can expect healthier plants. When you use the best possible soil, your plants are less susceptible to damage from things such as nutrient deficiencies or nutrient burn. You will also be able to increase your yields, which is very beneficial to autoflower growers since autoflowers tend to have lower yields than photoperiod seeds.

We know what soil not to use , but what type of soil should you use? The best mediums for growing weed come in many different forms, but the best ones all include a combination of compost, peat moss, perlite, and vermiculite. You can buy these specific soils, or you can make your own. We’ll get into how to make your own later.

A quick note on coco vs soil autoflower medium

As a newer grower, you might be tempted to try growing in coco coir. It’s not a bad idea, as coco coir is a fantastic medium for growing good quality dank buds. However, it is not recommended for newbies. Unlike premixed soil, coco coir requires precise and complicated nutrient formulas to give your plant the best environment. If this is your first rodeo, as they say, you might want to consider skipping the coco and opting for the soil.

Do Autoflowers Do Well in a Super Soil?

Autoflowers are incredibly hardy plants, and as such, they can handle many different types of soils. But if you already own less than optimal soil, you could have better results by using a super soil autoflower concentrate . Super soil is simply a soil that is made specifically for growing cannabis. The concentrate contains all of the nutrients you will need during your plants’ life; you’ll simply mix it with standard soil to create the optimal growing medium for your plants.

Many new cannabis growers may wonder why they should be concerned about a specific soil for autoflowering cannabis plants if the plants are already quite hardy. In other words, why should you go with soil specifically for cannabis? Think about the difference between eating locally sourced, organically grown fruits and vegetables versus eating the kind you find in the produce aisle of your grocery store. Which taste do you prefer? Think again about cannabis that you buy in the dispensary that was organically grown in the best possible medium, versus the ditch weed we used to smoke back in the late nineties and early aughts. It’s not that difficult of an answer if you think about it. Do you want your cannabis to resemble a five-star gourmet meal at a high-class French restaurant, or do you want McDonald’s? I think the world has enough McDonald’s, don’t you?

On that subject, it is appropriate to mention synthetic nutrients, that is to say, do not use them! While you might be tempted to play god, this is one of those cases where you should just let mother nature do what she does best and just let it grow. You don’t want synthetic ingredients, dyes, or any of that crap in your food, so why would you want them in your weed? Autoflowers are tough, yes, but that does not mean that they prefer the cheap stuff. They want the super soil.

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Organic Cannabis Soil Recipe

Avoid Common Mistakes

How to Germinate Autoflower Seeds in Soil

Contrary to popular belief, it is not advisable to germinate your autoflower seeds in soil. Many common garden plants can germinate in soil with no issues; however, cannabis is not your typical garden plant, not even autoflowers. As such, cannabis seeds require more care and attention than other seeds.

That’s why we recommend germinating your seeds in a jiffy pellet after soaking in distilled water for up to 24 hours, or in a damp paper towel (damp, not sopping wet!), though some seeds may take more time to sprout. Once your seeds have properly germinated, or “popped” to use the grower’s vernacular, you will need to fill some small pots with your soil mix. Bury your seed a half-centimeter or centimeter into the soil with the taproot (the little tail your seed develops during germination) facing downwards. Cover your seedling in a small amount of soil, but not too much!

Ideally, you should leave your seedling in the soil under a grow light until it emerges from the soil, and you can transplant it to its final growing place. If you don’t use a grow light, be sure to provide plenty of light. Make sure that your seedling does not get too cold or it won’t grow! It will usually take around 4-5 days for your plant to grow large enough for it to be safely transplanted. Make sure not to let your plant develop too much, or you will not be able to transplant it without causing damage. Let me repeat, it is vitally important that you not leave your seedling in the temporary pot for more than 6 days, or you will not be able to transplant them safely! Sorry to sound like a broken record, but this is a mistake that many new growers make. Ignore this advice, and you may be in the same boat.

How Much Soil Does an Autoflower Need?

Autoflowers are smaller plants than photoperiod plants, so they will not need as much soil, but it largely depends on how many you are planning on growing.

If you are wanting something like a mini desktop plant setup, where you are planning on growing only an ounce or less, then you will not need much, only about a half-gallon pot of soil. This quantity is excellent for people who are just starting out, perhaps only wanting to grow 1-2 plants for personal use. If you’re brand new to growing and don’t have a lot of time or money, or don’t really know if you’re going to like growing your own marijuana, then this is the size for you.

If you are planning on growing a bit more for your personal use, maybe less than five ounces, your best bet will be to go with a 2-gallon pot , which can yield you up to 112 grams or four ounces of high-quality herbs. Two-gallon pots are great if you have a little more room in your grow space and a bit of money to spare. Five-gallon pots are the standard that most growers agree is right for them.

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Five-gallon pots , while too large to fit on your desktop or windowsill, still fit comfortably on your balcony or patio, in your grow tent, or in your outdoor garden or greenhouse. A five-gallon pot will easily yield up to 8 ounces, which should more than cover the expenses of your growing equipment, plus save you plenty of trips to the dispensary.

Of course, there are other sizes. For example, photoperiod growers love 35-gallon pots , which will net you over a pound of marijuana. However, it is not a good idea to grow autoflowers in a 35-gallon container, as their life cycle is too short to warrant it.

Feeding your Autoflowering Plants

Now, let’s talk about how to feed cannabis plants in soil . Feeding is one of the most important aspects of growing any marijuana plant, but the process is a lot easier with autoflowers. You might think that they need a lot of nutrients like photoperiod cannabis plants, but this is not the case. Autoflowers need less food than photoperiods, and because of this, it is very easy for a new cannabis grower to overfeed their plants, which can lead to disaster.

The most important thing to remember is to keep an eye on your nitrogen levels as too much nitrogen can be devastating to small plants, such as autoflowers. Yet another reason why you should never ever EVER use MiracleGro, which is filled with nitrogen. Your best bet is soil that is designed for autoflowering cannabis and a guide, such as the Advanced Nutrients feeding schedule autoflower edition. Keep in mind, that calculator is intended for specific nutrients, which may not be ideal for autoflowering plants. However, it is a useful guide for showing how precise you should be when feeding cannabis plants.

There are other considerations to keep in mind, outside of nutrients. Experts recommend that you add mycorrhizal fungi to your soil. It’s important to note that these are not nutrients. They are simply organic lifeforms that break down organic matter in your soil and transport it to your plant’s root system. Though not required for your plant’s survival, it is a good idea to introduce these into your soil.

Another critical thing to keep in mind is the pH of your soil. The pH scale ranges from 1-14 with 1-6 indicating acidity, 7 being neutral, and 8-14 being alkaline. Cannabis plants like things on the more acidic side, so ideally, your pH should be anywhere from 6.2-6.5. Always test your plant’s pH regularly and make adjustments as needed. If your pH is too low, meaning your soil is too acidic, you can always add dolomite to it to make it a little more alkaline. If your soil pH is too high, meaning it’s too alkaline, add some pine needles to set it right where it needs to be. pH testing strips can be purchased in most stores, so be sure to pick some up if you’re creating your own soil.

Popular Soils for Autoflowering Cannabis Seeds

There are plenty of soils that are suitable for growing autoflowers. Let’s take a look at some of the pros and cons of each. A Nature’s Living Soil autoflower review on shows that the soil is generally great for their plants, but others have said that they couldn’t tell if it made a difference in their plants whatsoever. One reviewer even claimed that their plants were actually nutrient deficient from it. One of the most popular potting soils used for growing marijuana is Fox Farm Ocean Forest soil and Happy Farm Organic potting soil . Looking specifically at Fox Farm soil autoflower , there were many positive reviews; however, there were also quite a few that said it was quite a bit more than what they were wanting to spend. Overall, it’s a fantastic soil, but is the price worth it?

Many of the soils that you find online will say the same thing. Unless you want to spend a lot of money, you might end up with something that doesn’t do enough or does too much, potentially harming your plants. That’s why some growers choose to make their own soil. So, how easy is that, and does it involve math?

How to make the best Autoflowering Soil

Knowing how to make your own soil is a useful skill, even if you never end up needing to do so. At a minimum, it helps you recognize what to look for when you purchase soil. When you know what is supposed to be in your soil, you can choose which ingredients you want, depending on your tastes. Add what you want and leave out what you don’t. The best soils for autoflowers can have up to 17 ingredients in the substrate.

As a general guide, the following formula is recommended. Start with 3 parts peat moss, 3 parts compost, 2 parts perlite, and 1 part vermiculite. You’ll want to use the following process. First, start by spreading out the soil. Then, add the first ingredient and mix well. Repeat this step for every ingredient. Once you are done, you should wrap the mixture with a tarp, then allow it to sit for 24 hours. This process is called “cooking the soil.” It helps ensure your soil is well blended and ready to support your plant.

When the time comes to plant, fill your container one-third full of your soil mix, then fill the rest with topsoil. Doing so will encourage your plant to grow downward into the soil, using nutrients as needed. This step prevents your plant from taking in too many nutrients at once. You don’t want this because it could damage your plants.

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The Best Soil For Autoflowering Cannabis Plants

Autoflowering strains attract many cultivators due to their rapid growth and small, easy-to-manage structures. If you’re planning to grow an autoflowering variety, use this soil mix for optimal results.

There are quite a few differences between autoflowering and photoperiodic strains, the most notable of which being that the former initiates flowering without a change in light cycle. Autoflowering strains received this unique trait from a cannabis subspecies named ruderalis, which evolved in the colder climates of Central and North Asia, experiencing endless summer days and long winter nights. This subspecies has since been crossed with many sativa and indica strains to create legions of popular hybrids.

As well as having the unique autoflowering trait, these varieties have different needs and demands compared to standard photoperiodic strains, including the type of soil they require to thrive. Their hardy nature allows them to tolerate poor soils and harsh environments, but providing them with high-quality soil and nutrients in the right quantities will result in superior yields.


It’s true that most autoflowering plants can tolerate heavier soils, but they much prefer a substrate that is light and airy. When cultivated within such a growing medium, the roots of autoflowering strains can easily penetrate the soil, where they anchor the plant securely in place, mine for nutrients and water, and intake oxygen. By using light soil, you’ll be providing your plant with a perfect foundation for healthy growth. This kind of medium also allows for good water drainage, which can help to prevent detrimental conditions such as root rot.

An ideal potting mix for autoflowering strains should include peat moss, a substance that is harvested from peat bogs and is formed from decomposed moss. Another primary ingredient in autoflowering soil is compost, a resource that can easily be made at home by composting waste organic matter such as kitchen scraps. Secondary ingredients in the potting mix should include perlite, which is an amorphous volcanic glass that helps create space in soil to increase drainage and aeration. Vermiculite is another key ingredient that provides aeration to the substrate.

These ingredients should be mixed using the following formula:

3 parts peat moss
3 parts compost
2 parts perlite
1 part vermiculite

It can be cheaper to make your own autoflowering potting mix when buying these ingredients in bulk. However, if you don’t have the time, you can purchase premixed soil.


Autoflowering strains have also earned their hardy reputation due to the fact that they can put up with little food. In fact, it’s very easy to overfeed autoflowers and damage them by doing so. Autoflowering strains are usually significantly smaller than their photoperiodic counterparts and therefore require much less feeding during their life cycle. Feed them very lightly, and be particularly careful of nitrogen levels during the vegetative phase. Many premixed soils will come with the correct levels of nutrients, and will often provide enough for plants to survive for multiple weeks. After this, add fertiliser sparingly.

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A good addition to autoflowering soil are mycorrhizal fungi. Although these life forms aren’t nutrients, they do help plant roots by breaking down organic matter into small and usable molecules and transporting them into the root system. Introduce these into the soil to assist your plant in making the most out of the potting mix.


The pH scale is a tool used to measure the acidity or alkalinity of a solution. All soil has a particular pH, which can be tested using probes or paper test strips. The pH scale ranges from 1 to 14, with 1–6 indicating acidity, 7 indicating neutral, and 8–14 indicating alkalinity. All cannabis plants have a preference for slightly acidic soils within the range of 6.2–6.5.

Regularly test your soil with the tools mentioned above and adjust accordingly. If your pH is too low, try adding dolomite to bring it up. If it’s too high, pine needles can naturally work to bring it down a notch.

Best Soil For Cannabis – What is Good Soil For Growing Weed?

Signs of good and bad soil quality, other additives that help to improve soil quality and what to consider when it comes to planting this year.

  • 1. The benefits of organic soil
  • 2. Other additives that improve soil quality
  • 2. a. Coco
  • 2. b. Biochar
  • 2. c. Perlite
  • 2. d. Vermiculite
  • 3. Signs of good soil
  • 4. Signs of bad soil
  • 5. How to make your own soil
  • 5. a. Best nutrients for soil
  • 5. b. Cheap mix for diy soil
  • 5. c. Best soil for beginners
  • 5. d. Ph too high or ph too low
  • 5. e. Best soil for marijuana
  • 6. In conclusion

When growing autoflowering Cannabis plants, it is very important to keep them supplied with nutrients in the form of hard foods, or liquid feeds. The best soil for autoflowers will depend on your environment, fertilizers, and ability to control the pH, so keep this in mind if this is your first grow cycle, knowing the best option in your case can really set you on your way to bountiful harvests.

So if you’re wondering what soil is best for growing weed, below we’ll explain what to know, the signs of good and bad soil quality, as well as what you should consider when it comes to planting this year.

1. The Benefits of Organic Soil

Soil for autoflowers or for any other type of cannabis plant consists of organic material that is in a permanent state of decomposition. Teaming with beneficial microorganisms that are responsible for converting nutrients to the plant’s roots, living soil is Mother Nature’s way of allowing autoflowering plants to work in a symbiotic relationship.

As the tiny microorganisms decomposing the organic matter, they make the nutrients available for the roots, which are now able to access all the available nutrients and minerals found within the soil web.

Once this symbiosis occurs, then the only real requirement is for the soil to be adequately watered. This is basically the most simple form of organic growing that is perfect for those new to growing, it requires very little maintenance, and labor, as well as allowing the grower to work with a slow buffering organic process, so if you were wondering what is the best soil for growing weed, read along.

2. Other Additives That Improve Soil Quality

One of the downsides to using soil found in the ground is that it can be very dense once watered. Restricting root growth during the early stages of a Cannabis plant’s life is never advised, so adding other substrates into your living soil can be very advantageous.

By simply adding a 25-50% ratio of coco coir to your cannabis soil, the quality of the mix will become very airy and lightweight. Adding coco will enhance the air pockets present, the wicking action of the medium, as well as encourage a mass expansion in the rhizosphere. Coco is very user-friendly and is well associated with large yields.

The best thing about adding coco is the fact it is an inert growing medium, so does not have any nutritional value in terms of Nitrogen, Phosphorus, or Potassium, including trace elements.

  • Increases aeration and holds water better: Due to its characteristics, coco fiber can increase aeration in the soil and can absorb up to 10x its own weight in water, making it vital for growers living in dry weather.
  • Cheap: Coco fiber is relatively cheap and comes in various forms. You can find it compressed into a brick or already washed and ready to use out the bag, the price may change a bit depending on your preference but it won’t be absurdly expensive.
  • Easy to use: Coco is a sterile medium so fungus and other bugs avoid it, making it perfect for growing cannabis. Also, because of its neutral pH, you can use it with soil amendments without worrying.
  • Sterile: Because this type of medium is sterile, it won’t contain any of the nutrients your plant needs, even though you can mix it with soil or even amend it, you will have to provide all the nutrients your plant needs if you’re only using coco.
  • Needs to be washed: The quality can vary from brand to brand, so depending on the brand, you will have to soak it and wash it a couple of times to remove impurities before using it.
  • Hard to find good quality: Even though it’s relatively easy to find coco coir, it can be hard to find good quality coco fiber. This doesn’t mean you can’t use it but you will have to wash it thoroughly and experiment with a couple of brands before you’re 100% satisfied.


An incredible organic addictive that has amazing water-holding capabilities, an enormous surface area, and is a source of pure carbon. Biochar is made by heating wood to such temperatures that the end result is a tiny, charcoal-black crystalline substrate.

Due to the fact it is 100% carbon and has a shelf life of thousands of years, organic farmers use biochar with their soil to improve water retention allowing for less watering times, feeding the beneficial microorganisms a rich source of carbon, and helping save the planet.

Organic additives like Coco Coir and Biochar can drastically improve the quality of your soil, improve water retention and not to mention help you to save the planet.

  • Increases soil fertility: Biochar can boost soil fertility when used in combination with amended soil because it prevents nutrients from leaking out and provides carbon which increases the availability of nutrients in the medium.
  • Holds nutrients and moisture: Thanks to its porous surface, biochar can absorb a lot of water and draws in minerals which are essential for plant development.
  • Reduces the need for fertilizers: Because biochar is carbon-rich, it accelerates the decomposition of organic matter which results in more nutrients being available in the medium, a perfect choice for organic growers.
  • Can affect yields: Due to the porous characteristic, biochar can absorb too much water and nutrients when used in excess and can end up stressing your autoflowering plants which will show signs of deficiencies .
  • Can be contaminated: The quality of biochar is influenced by the material it is made of, so it can come contaminated with heavy metals or harmful compounds that are bad for your autoflowering plants.
  • Harmful to humans: If not dealt with caution, you can end up breathing ash which is a concern if exposed to daily, also, it can irritate you if it comes in contact with your eyes or skin for a long period of time.


Perlite is usually used in soil mixes to increase aeration and improve the soil’s texture, by using perlite in the proper amounts you will not only improve drainage but also avoid compaction, making it a better medium for the roots to grow in.

Usually, perlite is used in combination with coco fiber and soil to provide the best medium for the roots, while perlite improves aeration, coco fiber absorbs water, balancing those two elements in the best ratio possible.

Perlite can also be used to plant clones in, when you place your cuttings in perlite, the roots usually grow stronger and faster because they need oxygen to thrive and perlite helps provide it.

  • Increased aeration: Perlite creates small air pockets in the soil so if used properly, it can improve the growth rate.
  • Sterile medium: Because it’s a sterile medium, perlite won’t affect the pH of your medium or increase the amount of minerals in it.
  • Avoids soil compaction: Perlite needs to be thoroughly mixed in the soil before using, this will create several air pockets that make the soil fluffier, avoiding compaction.
  • Can dry the medium faster: You will need to check your autoflowering plants closely because with more oxygen in the soil you will have to water more often.
  • Needs to be washed first: If the brand you’re using does not pre-wash the perlite, it may come with a fine dust that can be harmful if inhaled so we recommend washing your perlite before using.
  • Needs to be watered more often: Because the medium will dry faster, you will need to water more and this means you will need to check on your autoflowering plants at least 2 times per day to make sure everything goes accordingly.
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Vermiculite can be used to improve the quality of your soil, just like perlite, vermiculite has several qualities that will make your autoflowering plants grow better and faster. This mineral helps aerate the soil, holds water and nutrients while not being toxic or changing the pH.

If your soil is compact or does not drain water properly, you can add vermiculite to provide the roots a better medium to grow in, just make sure you’re using the proper ratio because too much can hold a lot of nutrients and water and end up harming your autoflowering plants.

  • Neutral pH: Because it’s a sterile medium, vermiculite will not alter your soil’s pH so there’s no need to worry about checking the runoff every day.
  • Can prevent mold: When used in the proper ratio, vermiculite will absorb the excess water, preventing mold and fungus in the soil.
  • Improves soil quality: Just like perlite, vermiculite improves the soil’s texture and makes it fluffier, preventing soil compaction.
  • Can be expensive: Depending on where you live, vermiculite can be relatively hard to find and a bit expensive because it’s not usually found in regular grow shops.
  • Can affect autoflowering plants if used in excess: Because perlite holds nutrients and water, using it in excess can ultimately result in overwatering and overfeeding .
  • It’s said to be harmful: When buying low-quality vermiculite, it can contain asbestos and can cause lung problems. Inhaling these tiny fibers can cause asbestosis, mesothelioma, and lung cancer if exposed for a long time so it’s essential to buy the best quality possible and wash it before using it.

3. Signs of Good Soil

Due to the process in which soil is naturally produced, there are a few factors to consider if you are going to prepare your own. If buying soil from a well-known brand, or your local garden center’s cheap and cheerful products then there are some things to consider.

✔️ Check the packaging to see the nutritional value of the soil. A good brand will take the time to display a soil nutrient analysis displaying-N-P-K values, amount of perlite, vermiculite, compost, trace elements, and the bacterial and fungi count present.

✔️ Worms aerate the soil as they crawl through eating up organic matter. If you see your soil full of worms then do not worry. Not only will these little helpers aerate the soil but will release beneficial bacteria from their gut as they do.

✔️ Good store-bought soil will have perlite or coco added allowing for the ideal balance of air to water retention. Avoid soils that do not have any perlite unless you are purposely buying pure worm castings.

4. Signs of Bad Soil

❌ Bad soil will have an unpleasant smell which is a red flag bad bacteria are present, causing the medium to be in an unfavorable acidic state.

❌ Drainage will be poor, causing the soil to become dense and heavy. This weight can restrict root growth and slow plant development down dramatically. The ratio of water retention, drainage, and wicking capabilities will all be out of balance.

5. How to make your own soil

To make your own soil mix you need to have in mind the conditions that you will have during your growing cycle, things like temperature and humidity may have an influence in the best mix, so make sure you know the conditions before mixing your soil.

Best nutrients for soil

We recommend always using organic nutrients when growing in soil because soil it’s organic matter and contains microorganisms that can greatly benefit your autoflowering plants if taken care of properly.

We cannot recommend a certain brand or organic nutrients line but as long as you’re using high-quality organic nutrients and use them appropriately, you’ll be fine.

Just make sure the nutrients are 100% organic and keep an eye on the pH level because a drastic increase or decrease can ultimately kill the microorganisms present in your soil.

Benefits of good quality soil and what to keep in mind when you’re looking for the best soil for cannabis possible.

Cheap mix for DIY soil

Even though you can find organic nutrients in your local grow shops, they can be quite expensive so if you’re on a budget there are good alternatives that are relatively cheap.

There are several other methods to make your own organic nutrients such as KNF and Bokashi.

Depending on the space you have available, you can try composting or vermicomposting, these methods allow you to make your own tailored organic soil that will provide everything you need without spending too much.

Best soil for beginners

If you’re a beginner grower and don’t know exactly how things work, here is a general soil recipe that will work fantastically in almost all types of weathers, just remember that as time passes and you get more experienced, it’s ideal you adjust it to your specific needs.

General DIY soil recipe mix:
  • 80% organic soil
  • 10% perlite
  • 10% coco fiber

Remember that you can and should tweak it to your needs, but as long as you maintain a similar ratio your autoflowering plants will grow exceptionally.

PH too high or pH too low

If the pH of your medium is too high or too low, you should check the nutrient solution you’re feeding, have in mind that most additives are sterile and neutral so if you’re experiencing pH problems you should check the water source and nutrient solution.

Best soil for marijuana

The best soil mix for autoflowers or best marijuana soil, in general, will depend on the weather you have throughout your grow cycle, by following the table you can easily choose the one that better suits you.

Advantages of soil additives when growing autoflowering plants
Additive When to use Advantages
Coco fiber Use in dry environments or to improve soil quality. Holds water and helps avoid soil compaction.
Biochar Use in dry climates or when growing in organic soil. Improve water retention and helps decompose nutrients faster.
Perlite Used to help aerate the soil in humid environments. Helps dry the soil faster and increases aeration.
Vermiculite Used in dry environments, helps keep the soil moist. Improves soil quality and helps keep it moist.

As a general rule, you should always use 70-80% of organic soil mixed with the additive of your choice, always have in mind to use additives with different properties, for example, vermiculite shouldn’t be used with coco fiber because both absorb a lot of water and can cause overwatering.

  • 70% organic soil
  • 15% perlite
  • 15% coco fiber or 15% biochar or 15% vermiculite

For the best soil for autoflower plants, we recommend using 70-80% organic soil mixed with 15% perlite and 15% coco fiber, or substituting coco for vermiculite or biochar, always respecting their properties to avoid having oxygen or water in excess.

Remember that for the best growing medium for autoflowers, you should be on the lookout for the tips your plants give you and adjust the ratio if needed.

6. In conclusion

There isn’t a best soil for weed, in general, having all of the nutrients covered is one-half of a top-quality soil for marijuana, however, it should also have the ideal ratio of drainage, air pockets, and wicking action so we recommend looking into super soil for autoflowers.

Once you have found the ultimate balance, you can now confidently re-use your organic growing medium for multiple crops with the understanding the more time the living soil food web has to develop, the greater the results in terms of plant performance and yields.