Organic Cannabis Soil – Making Your Own

The last ten years have seen a growing trend in building organic cannabis soil from scratch across the global marijuana cultivation community. This has come amongst a wave of shared knowledge from interconnected cannabis scenes worldwide but has also been influenced by traditional agricultural techniques from Korean Natural Farming.

Why Build Your Own Soil?

It is fun, sometimes frustrating, but eventually (if you get it right), it is wholesomely rewarding. The benefits to building your own soil quickly stack up for the keen hobby grower and the no-stone-left-unturned-to-get-the-best connoisseur. Nature really can produce some of the best.

If you know exactly what is in your soil, you know exactly what is in your weed. It’s a simple equation, but it works very well and stays true to form. With so many bottles on the shelf and different bags of soil to choose from, it can be hard to know what you are actually buying and using to grow. If you care about the climate and wildlife ecosystem, building your own soil may just be the good karma you are looking to add to your garden.

Environmental Impact of Making Your Own Soil

Ninety percent of the soil available to hobby and indoor growers, and even your commercial outdoor for your back garden pansies come from peat moss, also referred to as sphagnum, as this is the majority of the moss species contained. This consists of decayed sphagnum moss that grows on marsh and wetlands. It is beneficial as a growing medium, as it provides an almost perfect structure for roots to grip on to and grow through whilst being on the acidic side, which is suitable for growing cannabis. 

It takes quite some time to decompose naturally into the state that it is suitable to be harvested for production. The problem comes with being harvested at a much faster rate than it can regenerate. In other words, it is entirely unsustainable. But why does that matter? It is just dead moss, you might say. Well, it isn’t quite that simple. 

Marshlands are home to many wildlife, especially birds and the fish and insects that they feed off, contributing to the conditions that turn it into peat. It is its own ecosystem and food chain. With this disruption, this beautiful part of nature is thrown out of balance, even causing some birds and insects to be at risk of becoming extinct. Their biodiversity needs to be protected. Climate change already impacts water levels which can cause mass disruption to peat bog habitats before the over-harvesting causes further issues. 

If cannabis culture is supposed to be about love and peace and respecting nature, we need to break our serious addiction to peat-based mediums for growing our ganja. The UK government has taken note of this and is implementing a ban on the sale of peat-based soil starting from 2023 – so if you haven’t started looking for an alternative already, you may have just landed in the right place at the right time. Get ahead of the curve – there is still time to get on the build your own soil bandwagon. 

Now What?

It looks relatively simple, get the ingredients and throw them together and you have some premium soil…well, yes, but no. There’s a great calling for nuance. This means you need to work out how much each component you will require. While some recipes are dotted across the internet, the quality and potency of the starting materials most people can access can be varied, so there will always be a slight difference in exact amounts to use. But that’s the great thing about hobby growing – you get to research and design and redesign until you get what you are happy with. Just don’t forget to take your own notes!

Most experienced soil builders will suggest that you “brew” or “bake” your batch before using it to plant your seeds or transplant your rooted cuttings into. Brewing or baking soil is the process of allowing the mix of nutrients, microbes and other building blocks to start breaking down and fermenting into constituents that are more readily available and easily absorbable by the roots. This will also help prepare to build the necessary healthy rhizome sphere when you introduce your plants. It’s not a complicated process and just requires a little time and patience. This process is sped up when you choose to inoculate the mixture with beneficial microbes like bacteria, fungi and enzymes to create the biological process required to sustain healthy soil that can deliver vitality to the plant. 

Potting On

Introducing your plants into unbrewed soil can result in nutrient lockout and cause the leaves and stems to show several deficiencies. So I would always recommend taking the time to add this step in. Some gardeners discover that small plants with underdeveloped root systems can also find freshly brewed soil a little too strong to start with, so making sure you have multiple thick white roots on your transplants is going to do you a favour.

I can offer one piece of advice: if you feel like your brewed soil is still too strong, try to grow some other plants in it first. A cover crop of companion plants works well. This can be edible or not. I’ve seen legumes, tomatoes and rye grown in 50-100l fabric pots before the cannabis crop goes in, but I have also seen basil, alfalfa, and clover be grown in them and right the way; through the whole crop too! The herbs can aid in keeping certain pests away due to their high essential oil content. The cover of the top of the soil is also protected from drying out too quickly if your temperatures are high, allowing the conditions for the microbes to keep the soil healthy and thriving.

Whilst the ingredients you put into the soil will most probably sustain the plant for its first two or three cycles, there is always the potential to top up the nutritional value via aerobic teas. You can use different ingredients for each stage of the plant’s cycle, so you can give it the right boost at the right time. It is quite as simple as finding ingredients containing the N, P, K or other elements you want to add and making a tea out of it. 

After the Grow

Once you have harvested your plants, you DO NOT THROW AWAY your soil. Reuse it. You have not got a useless ball of mud there now. You have the building block for sustainable cannabis cultivation – all you have to do is keep feeding the soil. This may be a “there is no spoon” moment for you because up until now, you have only ever thought about feeding your plants. The truth is they feed themselves; you just need to put the right environmental factors in place for them. 

Either continue to top-dress the original starter ingredients onto the top of the soil and water them in, giving it another rest time to brew or, feed it teas as you have been doing. This works well for some gardeners – others find the breakdown and mix up method more favourable. This process does what it sounds like and requires you to dig out your felt pot and bust apart the structure and the roots from the last grow. This isn’t personally my favourite method as it disturbs all those microbial colonies and fungal networks that have established themselves in your first cycle, which will then take a few more weeks to start to reinoculate. With the tea method, you really can be ready to go again straight away.

You will most likely find that some compression starts throughout the cycle due to the watering and the sequestering of nutrients from the medium. It would be a good idea, in this case, to make extra to top up the pot.  

Ingredients for Your Soil

Spent mushroom compost (straw, chicken/horse manure, gypsum). Great for providing the base carbon structure with your soil will need. Warning – there’s a lot of mushroom compost out there made with peat moss…for obvious reasons, we want to try and avoid this, so we know how to be sustainable in the future. 

Pumice. Introduces air pockets for drainage and harbour microbial life.

Calcified Seaweed – a coral-like seaweed that ground down is a source of calcium, magnesium carbonate and other trace elements.

Gypsum – a natural buffer to help maintain a neutral pH. You don’t want to overdo it with this, though, as you will make it hard for the plant to get the right conditions to produce enough flowers. 

Neem Cake – a good addition and amendment to act as a natural pest deterrent. Many insects cannot stand neem, so soil dwellers won’t set up home if you introduce this from the start and keep a mind to top up its levels with the other amendments. Neem cake also has potassium and phosphorus in it, which helps for strong roots and big fruits.

Kelp Meal – this seaweed has great biostimulants, natural plant hormones great for roots, and usable nitrogen levels. 

Rice Hulls – made of silica which is essential for plant cell structure. The form of the rice hulls also adds aeration to the soil. This is a suitable replacement for perlite, which can often rise to the top and leave the earth more compacted.

Crustacean Meal is an organic source of nitrogen, phosphorus, magnesium, and calcium, which is slow release. A favourite with tomato growers. 

Volcanic Rock Dust – contains several minerals, micro and macronutrients essential for healthy soil and required by plants to carry out vital functions. 

Insect Frass – dead shells and poo of mealworms interestingly provide great biostimulants to your recipe as well as natural levels of NPK in usable amounts. 

Biochar – burnt and charred wood created at the correct temperature will add biodiversity to your soil blend, allow microbial life to form big colonies in its structure and use their matrix to store nutrients until the plants need them. It’s like adding a battery to your soil. 

Earth Worm Castings – hopefully, you are already saving your vegetable trimmings and scraps for your home or allotment compost or worm bin. If you aren’t part of this tribe yet, get with us, your kitchen bin will smell less, and you will end up with free black gold for the garden. This stuff goes a long way and is everything you plants wish to feed it. 

Mycorrhizae – simply fungi that grow mainly on dead leaves. They form a symbiotic relationship with the roots to feed each other. 

Human/Pet Hair may sound odd, but hairs structure retains water.

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