Soil and Growing Media Thoughts
By Bill Drake and Authentic Genetics
Stony the worm from The Cultivators Handbook ©1970
Thoughts On Cannabis Container Soils
We get a lot of questions about the soils and amendments that we use and while we don’t have any special secrets we’re happy to share our ideas and experience. We’re also very happy to be able to include ongoing comments and new ideas on soils and amendments contributed by Authentic Genetics readers.
Buy It Or Make My Own?
Regardless of the size of your personal or small-scale grow - a couple of plants or a couple of dozen - we recommend using a high quality manufactured living soil, rather than creating your own, for any kind of container growing, indoors or outdoors.
While there are lots of recipes for making container growing soils, and some are very good, we’ve found that when you factor in the cost, the work and the results it doesn’t really save any money and it just isn’t worth it UNLESS you simply enjoy making everything yourself AND you have space to work AND access to quality ingredients like compost, manure, clean sand etc free or at a reasonable cost.
Our Recommendations
So to the point - the commercial indoor/outdoor container soil we’ve used for years, along with a lot of other experienced Cannabis growers at every scale, is the Roots Organics brand and we really like their LUSH soil blend which is designed specifically for large container Cannabis growing. We get multiple plant cycles with this soil with no problems. We believe that beginning with a rich, balanced and diverse soil microbiome maintains health, supports growth, and makes all the difference in flower yield and quality. Roots Organics uses high-end quality ingredients that create a complete living soil with balanced beneficial microorganisms. And no this is not a paid commercial - we like the stuff and people are asking us, so here goes.
What we really like about Roots Organics
Here are the ingredients Roots Organics uses across their different blends and what we think is important about each - please add your own comments and suggestions below.
Peat Moss - Peat and Sphagnum are the below-swamp and above-swamp parts of the same 350 species of moss plant that grow everywhere on earth in temperate zones. Sphagnum is harvested alive from above the surface and then dried, where Peat is dead and naturally decayed matter from the bottom of the bog. Sphagnum is pH neutral where Peat is tannic and acidic. Peat is a non-nutrient non-absorbent fiber that is great for aeration & texture, but as you can imagine with a product dug from the bottom of a swamp there’s lots of cheap crap on the market and Roots Organics uses clean, high-end Peat.
Horticultural Grade Perlite - a natural mineral that has been “popped” just like popcorn, it resists decomposition and has superior aeration qualities. Perlite quality varies and Roots Organics uses horticultural grade.
Coco Fiber or Coir - pH-neutral, non-absorbent, non-nutrient fiber that helps aerate the root zone growing environment. It varies widely in quality and Roots Organics uses top grade. Anything less and you can have serious salting up issues. As one Authentic Genetics reader said “You're better off paying the money for quality than spending a whole day washing and rinsing a cheap brick.”
Composted Forest Material - similar to forest floor composition, amended to create a fungus-rich environment; must be carefully composted selected materials to ensure slow release of beneficial tannins
Pumice - natural mineral similar in function to perlite but lasts longer and enables the fine hairs of the roots to grab better
Volcanic Rock Dust - full of trace minerals available to soil fungi and microbes for digestion and transport to the plant roots
Worm Castings - these are the magic ingredient in all soils but castings vary widely in quality from almost all dirt to pure castings. What the earthworms feed on matters a lot in the microbiome makeup of their castings and Roots Organics’s earthworms are fed a crafted diet. By the way, castings are completely different from animal manure which comes from digested living or dried plants while earthworm poop comes from digested decayed organic matter and soil minerals.
Bat Guano - this is a good source of nitrogen that is naturally “time-released” and it stimulates growth of beneficial microorganisms. The NPK profile of guano varies and how its sourced is environmentally important - another reason we like this brand.
Authentic Genetics readers have cautioned about using seabird guano - they tell us it’s persistent in the soil and stinks. We can see that easily. Ever walked too close to a seagull nest on the beach? That stuff they bomb you with is a bioweapon, not plant food.
NON-GMO Soybean & Alfalfa Meal - microorganisms break the protein molecules from these meals into amino acids, then break down those amino acids to create ammonium ions that become available as “slow-release” soil nitrogen.
Kelp Meal - helps to maintain pH balance and provides a wide range of readily available trace minerals.
Fishbone & Feather Meal - rich sources of available proteins for soil microorganisms. Feather meal is a slow-release nitrogen source and it's important that the source is organic not commercial poultry. Fish bone meal, different from fish meal, is naturally organic unlike most “bone meal” that comes from hormone-crazed, heavy-metal poisoned feedlot animals.
Greensand or "glauconite," is a key component for healthy beautiful Cannabis flowers. It’s a marine mineral rich in available potash, silica, iron oxide, magnesia, phosphoric acid, and 30+ trace minerals. Purity is important.
Beneficial mycorrhizal fungi: Funneliformis mosseae, Rhizophagus intraradices, and Septoglomus desertícola. Healthy fungi populations are critical to your plant’s absorption of minerals and nutrients.
Some Of Our Thoughts On Soil pH
Cannabis thrives when the soil is slightly acidic. If pH rises above 6.5 the plant’s energy progressively diminishes because essential minerals and nutrients become less available. The acid-based processes that absorb and transfer these essential minerals and nutrients are reduced and finally eliminated as alkalinity rises in soils. We agree with several comments from readers that a deeper understanding is needed by all of us of what pH is, how it affects Cannabis specifically and our gardens in general, and what growers need to know to manage pH in different environments. We’re working on an article to begin to address that.
The alkali flats of the Western US are an example of totally alkaline lifeless soil. Well, OK, there are plants that grow even in pure salt and alkali, but nothing you would want to smoke or eat.
So when the soil is mildly acidic, minerals like iron, copper, zinc and manganese become more soluble and more available to the fungi and microbes that translocate these minerals to the plant’s roots. There’s a balance however - too much of any nutrient, or an imbalance of nutrients, can lead to toxicity and growth disturbance.
One of the reasons that it’s so difficult to treat what looks like specific nutrient deficiencies by applying just that nutrient or micronutrient is that each nutrient functions as part of a soil/microbiome/plant ecosystem. Sometimes it’s perfectly possible to see a symptom, diagnose it and remedy it, but just like some folks take way more vitamins than they really need, some growers can’t resist using exotic plant growth supplements to tweak their plants. Not saying they can’t help - just saying that more vitamins don’t always make you more healthy.
That’s one of the main reasons that so many growers rely on earthworm castings and earthworm castings tea as a complete foliar spray - because the nutrients, minerals, enzymes and acids are always in perfect balance - nature’s balance. Growers will tell you that you can’t tox out your plants with earthworm castings, but please pay attention to the words “foliar spray”. Use worm casting tea only for leaf-feeding since nobody wants to spray earthworm tea or anything else on flowers that people are going to inhale or ingest.
You could even grow Cannabis in 100% earthworm castings if you wanted to - it would be pretty expensive and not at all necessary, but possible. Earthworm poop is the only poop that you can actually grow green plants in because truly is pure dirt - organic matter and minerals plus all the other goodies the earthworms found and ate and digested and pooped out while crawling beneath the earth.
Cow, sheep, horse, and chicken poop are all digested plant materials from above ground, but earthworm poop is digested dirt, minerals, fungi, bacteria, and decaying organic materials from below ground. Just intuitively, much less technically, you can see why worm castings are completely different from animal manure.
What has been your experience with worm castings?
A Few Cautions
Everybody’s working with a little different situation, and the Roots Organic soils that we like to use may not suit you, so if you’re looking around at all the available growing media options here are some things we hope you’ll pay attention to:
- Please stay away from cheap coco coir - it dries out fast and salts up because of the rapid surface transpiration
- How can you tell if it’s cheap stuff? Price and reviews. Growers who have used cheap Coir products are NEVER happy with their results.
- If you’re adding sand to any grow media use sandbox or playground-grade even in outdoors beds - never the much cheaper construction sand
- Construction sand is often dredged from river bottoms with who knows what kind of toxic contaminants.
- Non-branded bagged soils of anonymous origin should be viewed with suspicion and at a minimum checked for petroleum contaminants by putting a handful in a bowl of warm water, waiting a few hours and seeing if the surface shows any ‘rainbow’ effect.
- “Composted Forest Material” can mean anything from dirty chips and sawdust to rich soil-like organic compost
- Price is the give-away. It takes time and work to compost ‘forest material’ properly and you have to start with the right stuff, so there’s no way that good stuff can be cheap.
- Phrases like “municipal organic waste” don’t mean organic as in “pure” but organic as in ”not inorganic”
- When you consider what’s sprayed on most grass, yards, plants and trees in urban and suburban areas then you probably don’t want that stuff feeding your plants composted or not.
- Stay away from uncomposted organic matter, usually manure in some form, and even be careful of ‘composted’ manure that is often not composted well enough.
- It takes time and work to do right, to achieve the heat and bacterial activity necessary, so cheap manure ‘compost’ can be and usually is FULL of viable seeds, hungry bugs, and lurking pathogens.
- Unless manure is composted and treated it will bring nasty little visitors into your grow. Especially from cysts that are hard to kill, but that hatch beautifully with light, warmth and moisture. Again, price and reviews are your best indicators.
- Also keep in mind that feedlot animals are typically fed antibiotics and hormones which wind up in their poop.
- Too bad they aren’t fed organic hempseed - with apologies to our Vegan friends, think of those delicious steaks and burgers!
Is Lithium In Groundwater Worth Attention?
An Authentic Genetics reader brings up the question of Cannabis feeding on toxic heavy metal salts, which got us thinking about Lithium in groundwater. While the topic is not widely discussed, Lithium is a widespread and potentially important heavy metal in the environment that may be affecting Cannabis grows that depend on groundwater from wells. Water from public water system wells is treated for Lithium and other heavy metals but private wells may be another matter. Attention to groundwater quality clearly goes beyond Lithium, but we bring Lithium up here because it is less widely recognized and looked for as a possible growth inhibitor in groundwater, and it is widely distributed in Cannabis growing areas of the US.
We do want to say upfront that Lithium and most other heavy metal salts are easily handled by a good Reverse Osmosis system.
The good news about Lithium in the water is that there’s a lot of research that shows that people living in areas of high lithium content in the drinking water experience fewer suicides, fewer violent crimes, and fewer severe psychiatric events. Well, maybe so. El Paso is extremely high in Lithium, and their violence/crime stats are pretty cool. Then too, SoCal well water looks pretty rich in Lithium and there’s that legendary California mellowness, even before Cannabis. Hmmm. There’s also a lot of medical discussions around Lithium and Cannabis, but that’s not the focus of this article.
So human behavior aside, the mildly bad news for growers is that there’s a lot of research showing that Lithium is toxic to plants Here’s a graphic look at Lithium in the public water supply well water in Cannabis-growing states. Since lithium is toxic to Cannabis, with effects apparently ranging from asymptomatic to stunted wilted growth, if well water in these areas is being used without being filtered or tested and growers are having issues they might want to consider lithium as a culprit.
https://www.sciencedirect.com/science/article/abs/pii/S0048969720382243?via%3Dihub
Why We Think Living Soil Is Important - Outdoors or Indoors
Living soil for a plant is like breast milk for a baby - nothing is better, and nothing more is needed for a perfect start in life. If you start your plant out with living soil, you won’t ever have to waste your money on fancy soil supplements, plant vitamins, etc. You may want to, and you may feel compelled to, but you won’t have to in order to raise beautiful plants. If you provide clean water, strong light, comfortable dark, enough space, good humidity and moving air then the living soil will do its job and sustain the growth of this miraculous being.
Given soil, water and light, a Cannabis seed knows exactly what to do. There’s not a lot a grower needs to screw around with other than to be attentive to the basics and keep an eye out for diseases and predators.
If the soil is living and balanced the plant can take all the nutrients it needs to grow and thrive, with a lot of help from the soil’s living microbiome, but without a lot of “supplements” from the grower.
Humic acid is a great example. Yes it’s great for plants. In fact they can’t do without it. But wait a minute please. Humic acid is produced naturally during the breakdown of organic matter that along with minerals produces soil, and while Humic Acid is essential for plants, like a lot of nutrients for both plants and people, more is not better and too much can be toxic. If you are starting with and maintaining a living soil there will already be balanced and available Humic acid along with all the other essential nutrients that come naturally from living soil processes.
Toxicity can’t happen with living soil. The natural decomposition processes that create soil are driven mostly by bacteria, fungi, and earthworms. When the earthworms digest the decaying organic matter their gut works miracles including the production of just the right balance of humic acid and other acids and enzymes in their poop, all of which goes back into the soil where along with digested minerals and other good stuff it gets transported to the plant’s roots. In just the right amounts, in just the right balance. If your plants have a good living soil to feed on they do not need extra humic acid or extra much anything else - in fact, it could sicken or kill them.
An Authentic Genetics reader talks about Cannabis growers who “use 40 products for every function”. We’re reminded of snake oil. It always sold well at old-time traveling carnivals, and so did 5 cent Tickets to “See The Egress”. You paid your money and went through the one-way door to the outside. The Egress trick only worked once on the rubes and the carnies must have frequently had to leave town fast, but they also must have sold enough tickets to make it worthwhile because the trick is now carnival legend. We mention it because of what it says about gullibility and how easy it is for clever people who spot a widespread vulnerability to exploit it.
In the old days the carnies knew that people didn’t have a good vocabulary and were impressed by scientific-sounding words. Hence - they would pay to see the Egress. Today the equivalent of old-time carnies understand that people can easily become fanatical about their plants, which makes them vulnerable to “snake oil” advertising for those 40 products the reader mentioned. Not that all supplements are bad, or without real usefulness, or fake - not at all. As we know supplements are often the key to plant health and flowering. But what we’re talking about is the vulnerability of some growers, especially newbies, to the suggestion that maybe they aren’t giving their precious babies everything they need. Good advice to parents - calm down and relax and the child will do just fine. Good advice for us all.
Finally, another thoughtful Authentic Genetics reader commented that “Soil/organics brings out passionate fanatics, who in their well meaning earnestness, talk a lot of crap about soil/organic and frequently employ a full stack of the logical fallacies to defend/promote their beliefs.” Very true, and it happens everywhere in life doesn’t it? Passionate beliefs that you hold privately and share with others thoughtfully are wonderful, but when that passion turns into zeal to preach at others, the limits are quickly reached. Whatever works best for each of us is what’s important in the end, and sharing and discussing ideas is the way we all learn what’s best for ourselves.
Down The Rabbit Hole: Thoughts On Worms, Worm Poop, & Beautiful Flowers
Whether you have living earthworms or only their castings in your growing soil, indoors or outdoors, here’s our understanding of what goes on between earthworms, earthworm poop, soil fungi and microorganisms, the roots of your Cannabis plant, the light falling on its leaves and its flowers. We think it’s pure magic.
While passing earth’s organic matter and minerals through their amazing gut, that magic gut nurtures and multiplies the soil’s mycorrhizal and related fungi and hosts of beneficial bacteria while killing a wide range of pathogens. These energized fungi and microorganisms in turn produce acids that break down inorganic minerals like calcium, phosphorus, magnesium, zinc, copper, and iron along with all the vital trace elements, and then the fungi and bacteria work together to transport those absorbed minerals to the roots of the plant.
Why they do that is part of the miracle. We’ll get to that in a jiffy.
Those absorbed and transported minerals are why veggies grown in soil heavily treated with fungicides taste so bland - all the beneficial fungi and soil microbes are dead, so there are no minerals being transported to the roots of the veggies. Think of commercial vs garden tomatoes and you’ll understand exactly what earthworms and living soil do. Also hydroponic tomatoes vs soil-grown tomatoes - they taste different, right? The difference is that no amount of man-made chemistry can supply what the earthworm’s gut supplies nor can it replace the earthworm gut-to-fungi-to-plant root cycle in living soil.
Playing its part in this dance of life, the growing Cannabis plant sends most of the complex sugars it produces from solar energy falling on its leaves down to its roots, feeding and supporting the mycorrhizal fungi and the accompanying soil organisms as they increase mineral production to support growth and respond to the plant’s signals as the balance of its needs change from vegetative to flowering stages.
This downward flow of plant sugars is the reason the fungi and bacteria cluster around the plant’s roots in the first place, happily eating earthworm poop, digesting minerals, and trading those minerals with the plant for sugars. Minerals for sugars. It’s a solid deal for everybody.
Once the broken-down minerals are transported to the plant through its roots the process of chelation begins, with the plant again using solar energy to bind free amino acids to the minerals making them fully available for its use in growth and flowering. Plants need these organic minerals, along with other nutrients, to thrive, to grow and especially to flower.
Not at all coincidentally, all animals need these chelated minerals to survive. Plants are the only source of digestible minerals for animals - like us. We can’t get them from the soil, except maybe salt licks. No plants, no minerals, no sugars, no animals.
To conclude this discussion of soil, here are some very cool worm poop references - all peer reviewed journal research. Be sure to share links to your own favorite Cannabis soil and poop research references in the comments!
“Plant Growth-Promoting Rhizobacteria for Cannabis Production: Yield, Cannabinoid Profile and Disease Resistance”
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6698789/
This research discusses the wide range of biological soil processes and characteristics that impact Cannabis growth and flowering and that are affected by the mucous component of earthworm castings.
The mucous is the lining of the earthworm’s gut where all the magic takes place, that is steadily shed and mixed in with the minerals and organic materials the earthworms are consuming as they eat their way through the soil, leaving their mucus-coated castings behind. As we’ve noted above, the best soils are rich in earthworm castings.
“Effects of earthworm casts and compost on soil microbial activity and plant nutrient availability”
https://www.sciencedirect.com/science/article/abs/pii/S0038071702002791
“Role of earthworms' mucus in vermicomposting system: Biodegradation tests based on humification and microbial activity”
https://pubmed.ncbi.nlm.nih.gov/28822937/
“Disentangling the influence of earthworms in sugarcane rhizosphere”
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5156904