Best Compost and Fertilizers for Outdoor Marijuana Plants

If you are determined to grow happy and healthy marijuana plants, you probably have already been thinking about how to fertilize your soil.

Fertilizers of some sort (whether organic or otherwise) are very important to making sure your plants are receiving all the nutrients they need.

This article will give you an overview of the best compost and fertilizers for outdoor plants, paying special attention to the organic way of doing it with compost.

You have probably heard various facts and figures about composting and other ways of fertilizing your plants, but you’re not sure of what to do next. 

We can help you with that. Not only will we give you advice on how and why to fertilize your plants, we also sell the Bergman’s Plant Booster, and Bergman’s Plant Protector to help your plants thrive.

Compost and fertilizer

Because the composition of soil is so important to your harvest, it is key to take care when choosing what exactly to put in it.

Every grower encounters one main, important choice when deciding what they want their soil to be like.

Do you want to use chemicals, go organic, or go wild?

There is no single solution to this question – it depends mostly on your values and how much time and effort you would like to devote to it.

Mixing soil and compost for growing marijuana
Compost and fertilizer

Using chemicals means buying fertilizers in-store. Organic can be anywhere from natural fertilizers to actively composting.

And “going wild” refers to simply throwing the cannabis seeds wherever, and waiting to see how they function on their own.

The one with the best result is generally the organic option, although it is definitely not the easiest way to go.

You will be rewarded for your efforts: the taste and look will be very much improved.

If you are not willing or able to put in a lot of time or effort in your marijuana harvest, you might want to go with a chemical soil or store-bought fertilizers.

It is more user-friendly, making it the easy choice for people who are growing marijuana for the first time, and the package of soil even comes with a list of instructions and advice.

The package should be informative and useful in the decision-making process, as they inform you of the exact amounts of the different nutrients.

Chemical fertilizers are also a reliable option for people who are doing container growing.

The confined space of the pot or bucket means that it is essential to maximize which nutrients are there, so in this case store-bought soil is the best bet.

Marijuana Fertilizer

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Although the soil bought in stores is supposed to be of a balanced pH level, this does not mean that you don’t have to check it throughout the season.

Even if it starts out with a pH value of 7, it can easily change within one season, making it necessary to test it every now and then (read the article How to measure pH levels in soil).

Some store-bought soils are even way too acidic from the get go.

Depending on how things go, don’t be surprised if you find your plants and soil are lacking in a specific nutrient or two sometime during the growing season.

Growers with lots of experience already know that, if they use soil bought in the store, they will most likely have to use organic soil amendments in the end anyway.

Download my free Grow Bible for more information about composting and fertilizers.

Start composting

Composting is inexpensive and relatively simple, as it uses things you would normally just throw away anyway.

It creates the environment similar to a nice, fertile soil so your cannabis plants can grow healthily.

You can include anything from plant clippings to fruits and vegetables to animal manure.

It should not include animal fat or meat, however, as it simply will attract maggots and parasites.

You also shouldn’t include manure from your cat or dog, and consider not using pine needles because they lower the pH and don’t break down as quickly as other compostable items.

Composite made at home for growing marijuana
Start Composting

You should break down all of your compost ingredients into small pieces in order to accelerate the breakdown of your compost mixture.

There are plenty of different ways to go about it, and there are plenty of reasons for doing it in a new way.

There are several important factors you always need to remember.

For instance, it is a good idea to layer your compost pile, and you should always make sure that air is able to flow through it.

The last thing you want is a compost pile that has very little or no air circulation.

Just like with any soil or fertilizer, you should also be testing the pH level of your compost pile to make sure it remains balanced.

If it is too acidic or alkaline, you can simply put in some lime or bonemeal to adjust the balance in both ways.

Unless you live on a farm, you probably will need a long amount of time to collect enough diverse organic matter to form a useful compost pile.

Allow a few months to gain enough items to form a usable mixture.

The result is worth it, however, as your mixture will be much more fertile than most of the available store-bought items you can find.

Organic composting

The most often encountered reason for growing cannabis organically is that there is almost a zero chance that you will burn the marijuana plants.

Too much chemical fertilizer can be a bad thing, since it is highly concentrated and may leave salts behind in the soil.

The roots rapidly absorb the chemical fertilizers and, like someone who eats too quickly will experience a negative reaction.

This could include the death of your marijuana plants.

Mixing composite with soil for marijuana
Organic compost

Usually what happens is that too much of one nutrient prevents the uptake of others, leaving your plant deficient and dying:

When fed organic substances, marijuana plants will only take in the nutrients they need, leaving the rest in the soil.

The remaining nutrients are broken down slowly, which ensures a steady supply.

The major drawback to organic cannabis growing is the knowledge needed and the preparation that may be necessary to deliver the nutrients to the marijuana plants.

Composting takes time and should be started months in advance. It requires a space in which to accomplish this, preferably far away from people since it can carry quite an odor.

Also, depending on your security needs, it may be impossible to get the composted soil to the grow site, since where you compost and where you grow cannabis may be very far apart.

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In cases like these it is best to add individual organic matter to the existing site and bring that soil up to par.

The idea behind composting is that organic matter decays with the help of bacteria created in the decomposition process into a brown, loose blend called humus.

This is the same process that natural soil uses, though in nature it takes much longer.

You accelerate this process through composting because the mixture of things added increases the presence and activity of bacteria and microorganisms.

In good, fertile soil there are untold millions of microorganisms in every gram, as well as earthworms, which are attracted to good cannabis soil and improve it by living within it.

Make your own compost

Even if you are using chemicals to grow your marijuana plants, you probably will still need to include some organic compost additives at some point.

Below you will find a list of the various types of organic additives, and what they can do to help you with the specific elements your soil and fertilizers are missing. You need these to make your own compost.

making compost for growing marijuana
Making your own compost

There are plenty of other available additives as well, but this is a basic list that will help you make it through most seasons.

Read carefully, for some of the items on the list include valuable information, such as the exact ratios of Nitrogen, Potassium, and Phosphorous that they contain, plus which season they are the most useful in.

Blood meal nitrogen for marijuana plants
Blood meal

Blood meal

This additive includes a very concentrated amount of nitrogen. It is one of the most popular additives used for the cannabis vegetative growth period. Buy blood meal here

Bone meal for marijuana plants
Bone meal

Bone meal

Bone meal is a mixture of finely and coarsely ground animal bones and slaughter-house waste products. Buy bone meal here

Chicken compost for marijuana plants
Chicken compost

Chicken compost

Even chicken manure makes a great fertilizers. Organic slow release chicken manure compost increases yields and promotes healthy plants.

If you do not have a chicken at hand, DankoDirt makes great organic fertilizer. Learn about the benefits of ChickenFuel compost.

Decomposed fish for growing marijuana
Decomposed fish

Fish emulsion

As repulsive as it sounds, fish emulsion is a mixture that includes decomposed fish.

It is the most effective when applied to young cannabis plants, due to the fact that it is not as harsh as some other fertilizers, and its nutrient content is fairly balanced. Buy fish emulsion here

Worm casting for marijuana plants
Worm casting

Worm casting

A utility fertilizer that can be useful in any situation, worm casters are extremely balanced in their nutrient content.

In addition to nitrogen, potassium, and phosphorous, they also have micronutrients that provide a general nutritious value to the soil, helping it to remain nutrient-rich and healthy. Buy worm castings here

Kelp Meal for marijuana plants
Kelp Meal

Kelp meal

The Kelp meal contains many micronutrients and it is most effective when combined with a basic weed soil or compost mix.

Cannabis plants love it. Buy kelp meal here

Manure for growing marijuana


No two types of manure are the same since different animals produce waste that has different fertilizing properties.

In general, your best bet is to use either rabbit, cow, chicken, horse or bat manure.

They are all great additives for compost – don’t put them directly in your plants’ soil, however.

Using coffee grounds for growing marijuana
Coffee grounds

Coffee grounds

These are most useful when you need to change the pH level your soil or compost to be more acidic since coffee grounds have an extremely acidic pH content.

The right pH of the soil is very important to grow healthy marijuana plants.

Eggshells for marijuana plants


The answer to coffee grounds, eggshells can make your soil or compost more alkaline. They should be ground down and included in your compost pile.


Lime is another efficient way of increasing your soil or compost’s pH level.

Lsing lime for growing marijuana
Using lime marijuana plants

Plenty of organic marijuana growers swear by it when their soil is too acidic.

Not everyone loves it, however since its reaction and breakdown time is very slow.

Because of how long it takes, you should consider using it only early on in the growing season, or add it to your compost if you think the soil might be too acidic for some reason. Buy lime here

Wood ashes for growing cannabis plants
Wood ashes for growing marijuana

Wood ashes

This additive is a simple and very fast way of increasing the pH level. It also has lots of other health benefits and micronutrients for your soil.

FAQs About Compost and Marijuana

Is compost good for marijuana plants?

Cannabis plants benefit from different nutrient levels, Compost provides organic nutrients to your plants, hence using organic compost for your marijuana plants is highly recommended

What are the Benefits of Using Organic Compost?

There are many benefits of using an organic compost, but the biggest benefit is that your cannabis pant will only absorb the nutrients they need. and it will ultimately produce a high quality marijuana

How to start composting at home?

Building a compost bin, Place your bin in the garden, Place all kinds of food scraps and kitchen waste in this bin, make sure that the bin you are using has a lid (to retain moisture), and place bin on top of a grass or soil (that will allow easy access to microorganism)

Thanks for reading. If you’re interested in growing naturally be sure to read my complete guide to growing naturally.

Please leave comments or questions below and don’t forget to download my free grow bible


Avatar for Robert Bergman

Robert Bergman


Robert Bergman is an Amsterdam-based marijuana grow expert who has years of experience from small grows to massive operations ... See profile

29 comments on “Best Compost and Fertilizers for Outdoor Marijuana Plants”

  1. Once the supper soil is ready mixed, is there a temperature requirement? does it need to be protected from extreme heat? would it need to be covered?

    • Hi there,

      Thanks for your question. If you’re storing it, make sure to keep it in a cool and dark place.
      However, when you’re using it for growing right away, it will be fine as long as it stays in a range of 40-100F.

      Let us know if you have any further questions, of course!

      Happy growing,

  2. I have a question about using duck manure? Cause we had ducks but they died and im trying to grow marijuana… is it good for growing?

  3. First timer here starting with an Autoflower (white widow). Potting, using compost, outdoors, should plants be flushed before harvest? and, should a bloom boosting fertilizer be used at bloom time? Thank You!

    • Steve,

      Auto flower genetics do not require any special difference in regard to fertilizer. Just do not top it or transplant them. Any stress can lead to severe stunting of growth and could lead to small yields.

  4. Billionaire’s boy,

    Fertilizer or nutrients are available in such a wide range that I suggest you either join our forum at ILGM or visit our store and buy the Flower Power start pack. It is an excellent water soluble fertilizer good for soil or hydroponics. 🙂

  5. hi robert,just wondering what impact changing auto seedlings that have grown inside under 20/4 veg lights in 4inch pots, to 20 ltr finishing pots that are two big for my small grow closet, and leaving outside to finish even though start of winter here in aus. So prob will be going from 20/4 to 12/12 overnite. I realize their autos WW and GSC and are genetically programmed to flower, but is anything i can do to stop any degenerative changes, You have blown my newbie mind with all the info you’ve supplied with your bible and the comments from all ILGM people have made my transition from know-nothing to know-something a lot easier. Being a cancer survivor and finding this medicine really helpful, i just wanna say thankyou. Regards robert green

    • Robert Green,

      JUst FYI. 4″ pots are only used for starting plant. Auto flowers should be placed in non smaller than a 1 gallon but a 3 gallon is much better. “11-12 liters”

      On the other hand. autoflowers are not supposed to be transplanted or topped or be introduced to shorter photo periods.

      When moving from 20/4 to 12/12 the auto flower is going to finish. You most likely will not see a lot of new production. You could always make a structure that would allow to to light you plants 3 hours before Sun rise, and 3 hours after Sun down. Hope this helps, lw – I❤️GM

  6. I LOVE, LOVE, LOVE this site. My fruit mix (Strawberry, Blueberry, and Pineapple) showed up way too early, but that’s ok, I’m an outdoor grower in CO. So, I won’t be growing for the next few months, but, when I do… Nothing but natural for me. Llama poop and rain water, well maybe some compost 🙂 Anyway, my last adventure with “headband” produced a plant 3.5 m tall and about 2 lbs of bud. I can’t wait to see what the fruit mix does.

  7. thomas jones,

    I would hate to see a long question 😀 You are on the right track. I like 800 ppm throughout the flowering cycle of Autoflower genetics. Noting until 4-5 alternating nodes (true sets of leaves), then nothing the last week or 2.

    Might be a good idea to download and read our free grow bible, Or; join our support forum for more info.

    Happy growing, lw

  8. hi Robert ! just a quick question, with autoflowering, I am going with the assumption that the first weeks are just mineral water, maybe some VERY light veg feeding. this for 2 weeks maybe 2 1/2, then into light blooming feed until I am about 2 weeks away from harvest, the whole time lightly increasing my nute strength. the last 2 weeks of just mineral. now don’t forward a bunch of info on differents feeding formulas, maybe a few suggestions would be nice, but mainly just curious about most beneficial time tables to get the best results. thank you so much !!!!!! Tom

  9. I never received my free book. What happened? I really want my free book as it is promissed 100% guaranteed in this site.

  10. Not bad advice…I learned a little more on the organic compost..I live on a farm in KY. I put cow manure eggshells and ashes…started rolling it in February,so it will be good to go..I am transplanting from indoor ,natural sunlight…I have done indoor and outdoor ,for about 15 yrs. Still learning!! Love it…happy 420!! And 710!

  11. I really appreciate all your doing for the grow community.but please can you put more info out on growing using hydroponics it would be a big help thank you

  12. […] Without undergoing the extreme process of making Super Soil, you can easily make other types of organic soil that will similarly benefit your marijuana plants. These other methods will not require so much preparation, time, money, and space. At its simplest, you can combine organic soil that you combine with an organic nutrient. If these nutrients are liquid, you need to be very careful about regularly checking your pH levels. Read these recipes for the Best compost mixtures […]

  13. […] Without undergoing the extreme process of making Super Soil, you can easily make other types of organic soil that will similarly benefit your marijuana plants. These other methods will not require so much preparation, time, money, and space. At its simplest, you can combine organic soil that you combine with an organic nutrient. If these nutrients are liquid, you need to be very careful about regularly checking your pH levels. Read these recipes for the Best compost mixtures […]