Growing Cannabis in Coco Coir Slabs
Inicio » Crop articles » Growing Cannabis in Coco Coir Slabs
Today we’re going to talk about growing cannabis in coco coir slabs. It’s quite a simple growth method and has nothing to do with hydroponics; in hydroponics you need to strictly control your plants, their roots, the water temperature, and many more things.
Here’s a short list of the things you’ll need to begin growing in coco coir slabs:
When growing in slabs the first thing you need to know is that you’re growing in an inert medium. This means that it doesn’t contain any sort of nutrients or food for the plant, so your plants will be ready to accept whatever nutrients that you decide to give them.
There are growers that say that working with flowerpots and coco coir substrate is better than growing in slabs, but I disagree. Working with slabs has more advantages than disadvantages, as the slabs give your plants’ roots’ more space to grow compared to flowerpots; slabs offer more space even if you place more than one plant in a slab due to it being one big slab rather than a tiny separate flowerpot.
Another advantage is that when watering, all you need to do is prepare your fertilizing mix, stabilize the pH and check the resulting EC levels. Either way, you can forget about watering your plants one by one which saves a lot of time and effort.
I advise any grower that’s planning their first coco coir slab grow to pick a top quality water pump, an anti-obstruction filter, one or two airstones and their corresponding air pump so that the water in your pump is constantly oxygenated. You should also get some drip irrigation pipes with 12 outlets, which are the key to a successful slab grow.
As well as all of the advantages that we’ve already talked about, you’ll get much more yield, increasing the grams per watt ratio, obtaining more abundant yields of higher quality in around as much time as a hydroponic grow; you don’t have to pay as much attention as with a hydroponic grow but you can get similar results. Of course, I don’t want to discredit hydroponic growers here, I’m simply stating that it’s an easier method that offers similar results.
Something that you’re going to need to stay on top of is the height of your plants as they grow quire fast in slabs; the best way to control the height of your plants and the weight of the buds is by using a SCRoG mesh once flowering begins; you’ll manage to keep the height under control and increase the weight of your yield even more.
Author: Jesús, Growbarato Torrent.
Translation: Ciara Murphy
In this article we're going to talk about growing cannabis in coco coir slabs, an extremely easy method that is automatic and gives a high yield.
How to Grow Cannabis in Coco Coir
Table of Contents
Are you interested in growing cannabis with coco coir? Coco coir is a highly productive growing medium for cannabis that gives the experience of growing in soil, but many of the benefits of growing weed in hydro, including fewer bugs and faster growth.
A lot of cannabis growers have started using coco coir in their garden, but there isn’t a lot of information about exactly how to use coco coir for cannabis. It can be confusing since coco coir usually comes in dehydrated bricks with no instructions.
Coco seems almost tailor-made for growing cannabis… as long as you follow basic instructions.
What is Coco Coir?
Coco coir is made of ground-up coconut husks and works surprisingly well as a medium for growing plants. Roots love it. Coco is also more environmentally friendly than peat moss (one of its main competitors), and coco is slowly replacing peat in many soil potting mixes.
Note: “Coir” is officially pronounced “coy-er” but I’ve noticed most cannabis growers say “kwar” (rhymes with “car”).
Coco coir is a versatile growing medium which can be used by itself or mixed with other ingredients. It’s often included in soil potting mixes to help correct compaction and loosen the soil while still retaining plenty of water. For example, Fox Farm Coco Loco is a great choice for soil growers who want some of the benefits of coco.
However, this tutorial focuses on coco growing that doesn’t involve any soil or non-inert ingredients, in order to achieve the fastest growth. You’ll learn how to grow with a coco/perlite mix and provide nutrients in the water. This root environment creates thriving cannabis plants.
As long as you remember to water your plants with nutrients as directed, coco plants tend to be hardier than plants in other grow mediums. You typically won’t get bugs like in soil, or root rot like in hydro. It’s rare for a coco grower to run into major problems that prevent them from getting to harvest when they follow these directions. Because of that, I believe coco is one of the best grow mediums for new growers. Plus, you’ll learn almost all the skills you need to grow in soil or hydro in the future. Coco gives you a great base of knowledge for growing cannabis that will serve you well even if you branch out to other grow mediums.
Cannabis Plants Thrive When Growing in Coco Coir!
Why Use Coco Coir for Growing Cannabis?
- Feels Like Growing in Soil – Coco coir is a soilless growing medium that gives the experience of growing in soil. Plants are kept in regular pots, and growers simply water their plants with nutrient water. In most ways, coco coir can be treated basically the same as soil for growing cannabis.
- Great for Plant Roots – Coco coir tends to promote healthy and fast root development compared to other potting mixes. It holds onto moisture and nutrients, yet also has a light texture that gives roots access to oxygen, too. This makes plants less likely to experience symptoms from over or under-watering.
- Good for the Environment – Unlike peat, coco coir is sustainable for the environment. It also doesn’t have to be replaced every grow. Instead of breaking down like peat, coco coir is slow to break down and can be used more than once after a good rinsing.
- Does Not Attract Insects – Coco coir does not make a good home for many garden pests that affect soil growers. Cannabis growing in coco coir are much less likely to be attacked by pests or bugs.
- Plants Grow Faster than Soil – Coco gives a lot of benefits of hydroponics, which causes plants to grow fast by providing nutrients to the roots in the most easily accessible form. Plant roots don’t have to go out and search for nutrients, saving the plant precious energy. But growing directly in water can be complicated. Coco coir gives many of the benefits of hydro with a soil experience. This results in a quicker harvest and bigger yields for you as the grower.
Which Pre-Made Coco Mix to Get?
Although you can re-hydrate coco bricks at home, a pre-made mix takes out all the work! I highly recommend choosing a mix that contains both coco and perlite such as Mother Earth Coco Mix (70% coco / 30% perlite for growing cannabis. I’ve grown with Mother Earth at least a half dozen times and always get great results. Another pre-made coco mix I’ve tried that works great for growing marijuana is Roots Organics Coco Soilless Mix.
Cons of Growing Cannabis in Coco Coir
- Must Provide Nutrients from the Beginning – Coco coir is an inert growing medium with no inherent nutritional value, so growers must provide nutrients and manage pH throughout the grow. However, this is also the case for many soil growers as well. Unless starting with composted super soil and using high-quality water, most soil growers end up having to add nutrients and manage pH just like with coco coir.
- You Need a Cal-Mag Supplement – Cannabis plants grown in coco coir tends to need more calcium compared to other growing mediums, so usually, a standard “Cal-Mag” supplement is needed to make sure plants get all the calcium they need. These contain calcium as well as magnesium (which is needed for your plant to be able to use the calcium properly). Two great Cal-Mag supplements for cannabis are CaliMagic by General Hydroponics or CaliMagic by Botanicare. If you’re using a different nutrient company, chances are they have their own version of a Cal-Mag supplement. Whenever using any supplements, it’s a great idea to stick with the same company as your base nutrients in order to prevent the chance of unexpected interactions between two different brands.
- Coco coir usually comes in dry bricks, so the bricks have to be re-hydrated before you can grow plants in the coir (explained below, it’s actually really easy). However, if you don’t mind spending a little bit more, there are pre-made mixes with coco coir that are formulated specifically for plants like cannabis.
Coco coir holds onto a lot of moisture but also holds onto more air than similar materials, so your plant roots get the oxygen they need to thrive. When mixed with perlite, it provides an ideal amount of water and air for cannabis roots. Coco coir drains well so plants are less likely to get overwatered, but it also holds onto nutrients so you use less fertilizer.
Once your plants are in a good coco coir mix, you just add nutrients, water and light to get happy plants.
Although growing cannabis in coco coir is becoming increasingly popular, one of the problems is that there’s not enough free information to help new growers know what to do. It’s only a few simple steps get your coco coir mix in tip-top shape, and this tutorial will show you exactly how to do it.
Which Nutrients for Coco Coir?
When growing cannabis in coco coir, always use nutrients made for coco coir or hydroponics. Most growers also benefit from adding a “Cal-Mag” supplement, which is a common gardening supplement that provides extra calcium. Learn more about which nutrients you should use for growing cannabis in coco coir.
There are pre-made coco coir mixes, but they are usually more expensive than the cost to make a mix yourself. A pre-made mix is heavy like soil because it’s already been hydrated with water. This makes pre-made coco coir mixes expensive to ship, and heavy to carry around. If you’re willing to rehydrate your coco at home, you can skip paying a premium for water.
Everything you need to make your coco coir mix can be sent discreetly to your house. You just need some coir bricks and an airy bag of perlite which can be bought at any garden store. With this method, there’s no lugging a huge bag of potting mix home, or paying for shipping to have it delivered.
This tutorial will show you how to re-hydrate coco coir bricks and mix with perlite to create a rich, cannabis-friendly potting mix. I will also share some hints about growing cannabis in coco coir and how to take care of your plants for the best results.
If you follow these instructions, you will end up with 9-10 gallons of potting mix. I used this to fill four 2-gallon pots plus six solo cups, which is a perfect amount of soil for me to grow 4 plants.
Ready to start your coco coir tutorial? Your garden will thank you for it!
Coco Coir Rehydration Tutorial: What You Need
Make It Yourself (Instructions Below) or
Buy a Pre-Made Coco Coir Mix!
Mother Earth Coco Mix is a highly recommended pre-made coco coir mix for growing cannabis. However, many coco mixes work great for growing marijuana, including FoxFarm Coco Loco and Roots Organics Coco Soilless Mix.
The following tutorial makes about 10 gallons of potting mix. Double the recipe for 20 gallons!
For this tutorial, I used two bricks of a standard 650g Coconut Coir Brick. Any similarly sized bricks from a reputable company will also work.
I used “Nature’s Footprint” Coco Coir, but any 650g Coconut Coir Brick will work great!
I have used Shultz, Espoma, Black Gold, and even Miracle-Gro brand perlite. Any 8-quart bag of perlite will work. Perlite can often be found in garden stores or the garden section of places like Home Depot and Lowes. I normally advise against all things Miracle-Gro, but their 8-quart bag of perlite is okay for this tutorial if you can’t find anything else. But remember, never use Miracle-Gro soil or their standard nutrient formula!
Any bag of horticultural perlite from any manufacturer will work for this tutorial!
I use a 10-gallon fabric container from Mad Farmer (basically a Smart Pot by a different company) because it’s sturdy, has handles and will stand up on its own after adding coco coir. You could use a 10-gallon Smart Pot, two pillow cases stacked inside each other, or any other fabric container that lets water through and is tough enough to hold 5 gallons of soil.
Here’s the 10-gallon fabric pot & 5-gallon bucket in a bathtub
Note: You also need access to water and a drain for this coco coir tutorial.
Before You Get Started
Run your finger nails over a bar of soap . This adds a layer of soap under your finger nails, which will prevent coco coir from getting stuck under your nails. Save yourself the time it takes to clean your nails after you’re all done!
See What You’re Making
Makes about 10 gallons of potting mix
This will make about 10 gallons of potting mix, just enough potting mix for…
2 x 5-gallon containers
OR 3 x 3-gallon containers plus a little extra
OR 4 x 2-gallon containers plus extra
OR any setup that uses about 10 gallons of potting mix
Note: I hydrate the two bricks one at a time in the 5-gallon bucket because the 5-gallon buckets are easier for mixing in perlite, and the whole process goes by in less than a half hour anyway even if you do bricks one at a time. If you wanted, you could hydrate both bricks at once in a 10 gallon container, but that’s too heavy for me to work with 🙂
How to Rehydrate Coco Coir & Mix in Perlite
1.) Gather all materials and place everything near your tub (or wherever you’re going to rehydrate to coco coir bricks)
2.) Line inside of 5-gallon bucket with fabric container.
The inside of the bucket should be lined all the way to the top, and you need to have enough extra to be able to easily grab the top so you can lift it up later.
3.) Put the first coco brick inside the liner
4.) Fill the bucket halfway with water.
Optimally, you can add a Cal-Mag supplement and pH this water to 6.0 before soaking. This can help make sure your coco coir has extra Calcium and also help it get into the right pH range right from the beginning.
Honestly though I often use water right out the tap. You’ll be adding Cal-Mag and setting the pH later, but the “best” way is to start supplementing your coco coir now, and it definitely may save you time and trouble later.
You’ll see the brick almost instantly starts getting soft once it makes contact with the water.
5.) Wait 8-10 minutes or until the coco coir gets fully hydrated.
If you stick your hand in and there’s no more hard parts left, then you’ve waited long enough. The coco coir should feel soft all the way through the bucket. You can mix the slurry around with your hands to get it to break up faster if you’re in a hurry.
Some growers let it soak longer, especially if they’re using pH’ed water that’s been supplemented with a Cal-Mag supplement, giving the coco more time to “take in” the good stuff. But I usually wait about 10 minutes and go to the next step.
6.) Pull liner up and out, letting water drain .
First let the majority of the extra water drain out into the bucket, then place the liner in the tub or on the ground so it can continue to let water drain out slowly.
7.) Pour half the 8-quart bag of perlite on top of your coco coir
8.) Mix in perlite with hands
Make sure to mix everything thoroughly, and check around the sides too, where you’ll often find pockets of perlite or straight coco coir. It’s really easy and quick. Just stick your hands in and mix everything together until it looks even all the way through 🙂
This moving gif should hopefully give you an idea.
After mixing, your potting mix will feel light and kind of soggy. You should end up with something that looks like this.
9.) Fill your containers with potting mix
One batch makes about 5 gallons of potting mix, so it should easily fill a 5-gallon container. You could also use it to fill 3 x 2-gallon containers or 2 x 3-gallon containers, though in both cases you’ll be a little short.
Don’t worry if the mix feels soaking wet, it will dry in the fabric pots once you have a fan blowing over them in your grow tent.
10.) Repeat steps for second brick of coco coir & remaining half of perlite bag
Now you fill the rest of your fabric containers and possibly solo cups for seedlings.
Note: If you do use solo cups, make sure to cut holes into the bottom so that water can drain out after you’ve watered your plants. Always test to make sure water runs through cup freely. If you have a hard time filling up an empty solo cup with water because it’s running out the bottom, you have added the right amount of drainage.
Recap: Do you have everything you need to make your coco coir mix? You’ll need the following items to complete the tutorial above.
- 2 x 650g coco coir bricks
- 8-quart bag of perlite
- 10-gallon fabric pot
- 4 x 2-gallon Smart Pots (or a total of about 8 gallons)
- 5-gallon bucket
The above tutorial should leave you with about 10 gallons of potting mix.
Or Buy a Pre-Made Coco Coir Mix!
How to Grow Cannabis in Coco Coir
Now that you’ve got your mix ready (or purchased a pre-made coco coir mix), it’s time to start growing!
This isn’t the only way to grow cannabis in coco coir, but this is what I do and it works great. It directly follows the tutorial above for rehydrating coco coir and creating a coir-perlite potting mix.
Which Nutrients for Coco Coir?
Any quality cannabis nutrients made for hydroponics will work well as long as you also use a Cal-Mag supplement.
I personally like the General Hydroponics Flora trio plus Calimagic (a Cal-Mag supplement) for growing in coco coir.
This is a tried and tested nutrient system for any type of hydroponic growing including coco coir. You can actually follow their nutrient schedule listed on the included nutrient schedule; it’s formulated for plants like cannabis.
Note: After adding nutrients (or even if you’re giving just plain water), always pH your water to 5.5-6.5 before giving it to your plants. This is important!
Like nearly all cannabis nutrients, the included schedule is aggressive and can burn your plants if given with every watering. No matter what nutrient system you’re using with your coco coir, I recommend giving plain water every other watering to prevent nutrient buildup.
Whenever using liquid nutrients, you will need a way to test pH so your plant roots are able to easily absorb all the nutrients they need. I use a simple General Hydroponics pH test kit. Learn more about managing pH here: https://www.growweedeasy.com/ph
How much Cal-Mag should I use for coco coir?
Give Cal-Mag at full strength alongside your nutrients for at least two weeks at the beginning of your grow. You may also add Cal-Mag with your other other nutrients if needed throughout the grow, though you may want to give it at lower doses.
What Else Do You Need?
- Grow Lights
- Plant Containers – I like fabric pots
- Solo cups (optional)
- Rapid Rooters (optional)
If you followed the above tutorial to make your own coco mix, you’ll have about 10 gallons of potting mix. This can be used to fill 2 x 5 gallon pots, 3 x 3 gallon pots, or 5 x 2-gallon containers.
I recommend larger containers for larger plants and to water less often. I recommend smaller containers for smaller plants, and when the grower is willing to water more often.
Step-by-Step Grow Cannabis Coco Coir Tutorial
1.) Germinate seeds in fresh Rapid Rooters on top of the moist but not soaking coco coir in your solo cups. Some growers will plant their seeds directly in the coco coir, and that works well, too. You can also place the Rapid Rooters in a tray, making sure there’s a very shallow pool of water at the bottom to keep them moist. Fresh Rapid Rooters give some of the best germination rates, but of course there’s other ways to start your plants. Learn about other ways to germinate cannabis seeds here: https://www.growweedeasy.com/germinate
2.) After seedling grows first set of “real” (serrated) leaves, water with nutrients at normal seedling strength , and add a regular dose of Cal-Mag (Calimagic). Keep giving water until you get about 20% runoff out the bottom of the solo cup. The first set of leaves are round, but the second set are serrated and pointy. Once you see those leaves, it’s time to water your seedling with nutrients.
3.) Maintain seedlings. Some growers will put their Rapid Rooters in solo cups, while others put their seedlings directly in their final container. Either way, your job is the same. Make sure your seedlings get plenty of light while making sure that it’s never too hot for your seedlings. Place your hands where your seedlings are and wait 10 seconds, if it’s too hot for you, it’s too hot for your plants.
- Continue to water plants at full seedling strength of the included nutrient schedule for the General Hydroponics Flora Series plus Cal-Mag.
- When watering, keep giving water until about 10-30% extra runs out the bottom. Then don’t water again until the top inch or so starts feeling dry to the touch. If you notice water is not draining out, you need to fix that right away. Water should be able to drain freely soon after you start watering.
- Wait until the seedling has grown 3 sets of leaves…
3b.) If you started in solo cups, you should transplant to bigger containers once the seedlings have grown about 3 sets of leaves. Once your seedling has grown 3 sets of leaves, it’s time to transplant to a bigger container!
Dig a small hole in your coco coir containers so there’s room for the new seedlings. Take a butter knife and carefully slide it all around the edges of each solo cup, then carefully transplant your seedling into your bigger coco coir containers.
4.) Maintain vegetative plants until they are half the final desired size.
Cannabis nutrients tend to have schedules that give too high levels of nutrients for proper growth. If you’re using the custom nutrient schedule I created for you above, you can simply follow the instructions. But if you’re using a different nutrient system, I encourage you to start providing all nutrients in the water at half strength.
Continue to water plants with nutrients with 10-30% extra runoff. Continue to always adjust pH water to 5.5-6.5 before giving it to plants.
- If desired, this stage is when you start plant training (I recommend waiting a few days after the transplant to make sure plant isn’t stressed before starting any training).
Note: If you are growing auto-flowering plants from seed, it’s recommended you don’t use any plant training techniques besides LST.
- If you notice the lower leaves are starting to yellow, and the yellowing seems to be climbing up the plant from the bottom, it probably means you have a nitrogen deficiency. Look at the nitrogen deficiency page to make sure. If you have a nitrogen deficiency at this stage, it means your plants need higher levels of nutrients. If so, increase your nutrient levels slowly, watching closely for signs of nutrient burn (which means too high levels of nutrients). Remember that yellow leaves will likely not turn green again, so don’t look to old leaves for recovery. What you’re looking for is making sure the problem isn’t still spreading to different leaves. It’s also likely that any improvement may take a few days after you provide increased nutrient levels. So don’t keep upping your dose until you’ve given your plant a few days to a week at the new level!
- If you have any other problems besides a nitrogen deficiency, consult this page: https://www.growweedeasy.com/7-step-cure
- Once plants are half the desired size, switch to the flowering stage (if you have auto-flowering plants, they will automatically switch to flowering after about 3 weeks).
This stage lasts until your plant is about half the size you want it to be in the end. After your plant has grown half the desired size, it’s time for the next step.
5.) Switch to the flowering stage. With regular plants, you do this by changing your light schedule to 12-12 (12 hours of light, plus 12 hours of uninterrupted darkness). With auto-flowering strains the switch to the flowering stage happens without you needing to do anything. Learn more about cannabis life stages and switching the flowering stage.
6.) Maintain flowering plants until they are ready to harvest. Care is basically the same as before, except during the flowering stage it becomes more important to control temperature and humidity than ever. Cannabis plants are much more finicky in the flowering stage, and it’s easy to trigger problems if you aren’t controlling your environment. Watch over plants closely, and make every effort to expose all bud sites to light and a breeze. You can still train plants by gently bending too-tall colas, but avoid any major training once the plant has started making buds.
7.) Harvest buds when ready. This tutorial will explain everything you need to know about when to harvest your plants: https://www.growweedeasy.com/harvest
Here are some additional nutrient suggestions for growing in coco coir:
Nutrient Picks For Growing in Coco Coir
Often when growing cannabis in coco coir, it is helpful to supplement with extra Calcium and Magnesium as calcium deficiencies & magnesium deficiencies are relatively common in coco coir. There are many supplements that provide a boost of these nutrients, and pretty much all of them will work fine. A commonly seen one called “Cal-Mag” by Botanicare works well (and is pretty inexpensive), and so does “CaliMagic” from General Hydroponics. Coco coir is an excellent growing medium as long as you maintain the pH between 5.5 – 6.5 and make sure the plants have enough calcium and magnesium.
Any quality cannabis nutrients made for hydroponics will work well for growing in coco coir as long as you also use a Cal-Mag supplement.
I personally like the General Hydroponics Flora trio plus Calimagic (a Cal-Mag supplement) for growing in coco coir. This is what I use for my coco coir grow. You can follow the nutrient schedule provided by GH as long as you provide plain water every other watering. Or…
You don’t need any other nutrients to grow marijuana; the Flora trio + Cal-Mag will give your cannabis plants what they need to flourish through the vegetative and flowering stages.
For the easiest coco coir growing, get a smart pot (pot made out of fabric – they work perfectly for growing cannabis and have good drainage).
Ever wondered how to use coco coir blocks to make a cannabis-friendly rich potting mix? This tutorial breaks it down…