Plants need nutrients, water, oxygen, stable ground, and sunlight in order to grow and thrive.
But, as long as all the other needs are met, “stable ground” could mean a few different things: soil, coco coir, rockwool, or other substrates.
In a hydroponic setup, “stable ground” might just be a styrofoam block that your plant’s roots grow through down into a water tank – but let’s save that topic for another day.
Say you’re planting in pots and trying to choose your medium. Which is better: coco coir or soil?
What is Coco Coir?
Coco coir is a substrate made from processed, recycled fibre from coconut husks.
It’s better for the environment than peat moss (the main ingredient in most potting soils) is, because those coconut husks are a completely renewable resource, and husks that aren’t used as a substrate are usually just thrown away.
Coco coir is an inert growing medium, meaning that it doesn’t contain any nutrients on its own and is rather used as support for the plant’s roots.
Coco coir usually has a pH of 6.5-7.0, which is very comparable to unfertilized soil – although of course, the nutrient content is very different.
As a result, you’ll need to add nutrients yourself from the very beginning.
You’ll also need to spend some time preparing your coco before you even start planting seeds.
How to Prepare Coco Coir
You can buy coco coir in two basic forms: pre-mixed coco coir that comes in a plastic sack, just like soil, or compressed bricks of coco coir that you will have to rehydrate before using.
These compressed bricks can expand up to about 10x in size!
Dehydrated coco bricks are the cheapest option, and due to their small size and weight, they’re also the most convenient since they can easily be ordered online and delivered by mail.
However, you’ll have to do more than just rehydrate your coco before it’s ready for planting.
The first step (following rehydration) is rinsing.
When you get a brick of coco, it’s going to be full of coco peat – tiny, dust-sized particles of coconut husk.
Coco peat doesn’t aerate or drain as well as coco coir, and if you have too much of it in your mix your plants could end up drowning.
So, rinse your coco through a screen or colander to remove all the smallest particles.
Step two is buffering.
You’ll need to feed your cannabis plant from the beginning if you’re growing in coco, but your plant is going to suffer from nutrient deficiencies if you don’t soak your coco in a Cal/Mag (calcium/magnesium) solution before planting.
But wait – why is this Cal/Mag soak necessary?
Coco coir is covered in cation exchange sites that are naturally bound to sodium and potassium cations. However, these molecules have a weak bond to the coco’s cation exchange sites.
Once calcium and magnesium are present, the cation sites will release their sodium and potassium cations and instead bond to the calcium and magnesium – rendering those nutrients unavailable to your plant.
The Cal/Mag soak ensures that each of the coco’s cation sites is already full, so that when you add new calcium and magnesium you’ll know that it’s going to your plant and not the coco.
You can use tap water for your buffering solution.
Add at least 7.5 milliliters of a Cal/Mag mix per gallon of water, and make sure the solution’s electrical conductivity is between 1200-2000, and that the pH is above 6.2.
Remember, the cation sites on the coco just need to be saturated.
An excess of Cal/Mag in the solution won’t hurt anything but your wallet.
Soak your coco for 8+ hours in that mixture, and then drain.
Some growers recommend repeating this process twice.
Adding Perlite and Measuring EC
Following the buffering, you’ll need to add perlite to your coco mix.
This helps aerate the soil and improves drainage.
A 25% perlite, 75% coco mix is ideal.
Bagged coco may be pre-buffered, and should be pre-rinsed.
Double-check to make sure, but this is generally the case.
Regardless of what kind of coco you buy, it won’t come with perlite, so be sure to add some!
Finally, before you actually put a plant in your coco, measure the EC and make sure it’s in the right range for cannabis.
The Cal/Mag buffering solution is often pretty hot, so you may need to rinse the coco with plain water one last time before planting.
Growing Cannabis in Coco Coir
Coco coir is a bit like growing in soil, but also a bit like growing hydroponically.
You won’t need an elaborate setup with a water tank, pumps, and everything else, but you will still get to enjoy some of the benefits a hydroponic grow offers – the potential for faster-growing, larger, higher-yielding plants.
This assumes that you do everything right, but hydroponic setups afford growers the greatest degree of control over their plants’ environmental conditions.
Growing in Coco Coir – Pros and Cons
Pro: As it would in a hydroponic setup, your plant will grow faster in coco coir than in soil.
Pro: While coco coir can be hard to find locally in some areas, it’s super easy to order online.
Pro: Since coco coir is an inert medium, you’ll have complete control over the nutrients and pH in your plant’s substrate.
If you do everything right, your plant’s diet can be more perfectly finely tuned than it would be in soil. And a healthier diet means a bigger plant!
Con: Depending on what brand you buy, some coco coir is soaked in saltwater or treated with chemicals before it’s sold.
Unless you know for sure, it’s usually a good idea to rinse all your coco well before use.
Con: The fact that your substrate doesn’t contain any nutrients of its own means you’ll have to feed your plant more often and keep a closer eye on nutrient levels.
Growing in Soil – Pros and Cons
Soil isn’t just “dirt.” It’s usually made of some blend of compost, peat moss, and perhaps other organic material and beneficial bacteria.
Soil is obviously the most natural growing substrate, and it’s also the most forgiving.
Many growers say that soil-grown cannabis tastes the best, although soil-grown plants can’t get as big as plants grown in coco coir.
Pro: Growing in soil is the easiest method, and it’s also the cheapest, which makes it a great choice for beginner growers.
Pro: Good-quality soil should have some level of useful nutrients right out of the bag, so unlike with coco coir, you won’t have to add fertilizer to your plants as often.
Pro: Soil self-corrects its pH to some extent, so you’ll find that this is less difficult to manage than it is with coco coir.
Pro: Soil drains more slowly than coco, which means you don’t have to water your plant as often.
Con: On the other hand, slow soil drainage can cause buildups of mineral salts. If this happens, you’ll have to flush your soil to prevent nutrient lockout.
Soil vs. Coco Coir: Which is Better?
Alright, now for the real question: between soil and coco coir, which substrate is better?
It really depends on the situation – neither one is objectively superior.
You should go with soil if:
- You’re a beginner grower.
- If you want to grow the best-tasting buds possible.
- You don’t want to deal with rinsing and buffering coco coir.
- If you don’t have time to give your plants as much attention as coco coir requires.
- If you can only grow outside.
You should go with coco coir if:
- You want to grow a bigger harvest – without the difficulty of using hydroponics.
- You have time to give you plants more attention and water more often.
When it comes to choosing your growing substrate, coco coir and soil both offer different advantages and disadvantages.
Soil is more forgiving and may lead to better-tasting buds.
Coco coir is more time-intensive, but it’s quicker and grows larger yields.
Whichever one you pick, happy growing!
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Elijah Petty is a writer in the cannabis industry. He aims to use his platform to help educate people about cannabis and dispel some of the myths and misinformation that surround the plant.