How to grow marihuana with coco coir

Today, coco coir is the favourite substrate of many growers for growing cannabis, either indoors or outdoors. Although it is mainly used by experienced farmers, growing with coco coir is easy if you follow a few basic steps. Using EC and pH meters is almost mandatory if you choose this media, since you have to carefully check this values before watering your plants. In this post we tell you a few tips to successfully harvest your plants with coco coir.

All the pictures you’ll see were taken from Amnesika 2.0 crops, both in pots and coco slabs.

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Cannabis plants growing in coco slabs

What is coco coir?

Coco coir, or coir, is a natural fibre extracted from the husk of coconut trees and represents 35% of the seed. During decades, it became a major concern in countries like India or Sri Lanka, where the husk of the seeds was piled up creating a perfect environment for the reproduction of insects and rodents. Today, this residue is washed, dehydrated and pressed into bricks, thus getting a cheap, light and efficient growing media.

We normally find 3 types of coco coir: coco dust, fibres and bricks. The most used one in Europe is coco dust.

Coco is an inert substrate so we must pay close attention to the feeding schedule for our plants. In this way, if we are using pure coco coir we can talk about hydroponic techniques.

[caption id="attachment_8387" align="aligncenter" width="1024"]Philosopher Seeds Coco dust ready to be used

Advantages of growing with coco coir


The main feature of this substrate is its perfect water retention level and excellent oxygenation of the roots. This allows the plant to grow more vigorously and thus produce more flowers. Indeed, yields with coco coir are superior and some growers even claim that it shortens a few days the flowering period of plants.

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Growing in coco slabs

We’ll normally use smaller pots than those used with organic soil, getting the same results – or even better.

We can also use coco slabs, which come filled with coco coir so we just have to plug our plants and make a few holes at the bottom of the slabs to improve drainage. Slabs are practical and clean, since you don’t even touch the substrate at any time, and are ideal for using the SOG technique.

Another main advantege of coco coir is that it is reusable; we have successfully performed 3 crops with the same substrate and without problems.

Growing cannabis indoors with coco coir

Coco coir is formed by micro-sponges that can absorb up to 9 times their weight in water without losing its oxygenation capacity. This makes it perfect as hydroponic growing medium, also to mix it with soil and get a softer and lighter substrate.

Strains like Black Bomb, Orange Candy / Naranchup, Heaven’s Fruit, Sugar Pop or Amnesika 2.0 are strains that perform much better when grown with coco coir.

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Plants flowering in coco slabs

Philosopher Seeds
Amnesika 2.0 in coco coir

It has high contents of lignine, which promotes the presence of microbial life like Trichoderma, which creates a perfect symbiosis with the roots of the plants.

As we already mentioned, we don’t need large pots when using coco. Plants get bigger and grow more vigorously with this substrate, something to keep in mind especially if growing indoors. While we won’t have much problems with Indica strains, Sativas can grow too vigorously, so a very short growth period is advised when using mostly Sativa híbrids.

Depending on the number of plants per square meter, removing the lower branches is recommended to promote a single main cola or to enhance production on the tops of the plants.

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We pruned the lower branches

pH and EC for growing cannabis with coco

Getting the correct and stable pH value is essential when using coco, since plants need accurate values for proper nutrient uptake. Here you have a table adapted to all Philosopher Seeds hybrids.

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pH and EC in coco coir

Rehydrating coco bricks to grow cannabis

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Re-hydrated coco slabs

Coco is often sold as dehydrated pressed bricks, which are great because they are light, discreet and compact. The first thing to do is rehydrating the pressed substrate, soaking the bricks in a container large enough for the final volume of the substrate (it can easily quadruple its volume once hydrated). Generally, we’ll adjust the pH level of the water used to hydrate the bricks at 5.0-5.2, since most coco coir on the market is too alkaline for growing marijuana and we must lower its pH value a little bit.

When the substrate is spongy we can fill our pots. Some growers mix 90% coco with 10% perlite. When hydrating coco slabs, just make a small hole and soak them or use a hose to fill it with water. Wait some minutes and check the texture, which should be soft, spongy and moisturized.

How to water and fertilize cannabis plants with coco coir?

Philosopher Seeds
Cutting in rockwool cube plugged into a slab

The high absorption capacity of coco allows an extremely vigorous growth of plants. The ideal would be to perform several waterings per day, so using small pots and automatic irrigation systems is recommended for best results. Of course, we can also water our plants manually, but we’ll get better yields - and have less work to do - if we use an automated system. Water the plants until you see the pots draining. Stop the pump at this moment and now you know the exact irrigation time. Wait until the surface of the substrate is dry to water the plants again, which is easy since coco becomes clearer when dry. Now we know the time between waterings. You can increase this time with the lights turned off, or even not water your plants at all during the night period. Roots grow healthy and vigorously with this system!

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Continuous pH and EC meters

Since coco coir is an inert substrate, we need to use fertilizers from the start. There are plenty of different nutrients for coco on the market today, even organic fertilizers. We can find base nutrients, root stimulators, bloom enhancers, PK boosters, enzymes,etc.

We always recommend to check the pH and EC values of our nutrient solution when using this substrate, since plants depend on the nutrients we are providing and need certain values to grow properly.

The softer the water we use, the better, since in this way we can add more nutrients to our solution. An initial EC value of 0.4 would be perfect.

Add nutrients to the water until reaching the desired EC level. We recommend 1-1.5 for growth and around 2 during the bloom phase. Depending on several factors – genetics, growing conditions, etc. – these parameters may vary.

We’ll also flush the roots of our plants regularly to avoid any kind of overfeeding or nutrient accumulation on the growing media. Water your plants abundantly with tap water every 15-20 days and check the EC level of the drainage water.

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Automatic irrigation system for coco clabs

Also, flush your plants at the end of the flowering stage as you would do with any other type of substrate.

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Coco coir becomes clearer as it dries

Growing marijuana outdoors with coco coir

This growing media is also suitable for outdoor crops, achieving similar results than plants grown directly in the ground. If you can only grow in containers, coco coir is an excellent option.

It should be used in the same way than indoors, but we must pay attention to rains, which will flush our coco and leave our plants with no nutrients. If your climate is rainy, cover the surface of the substrate with plastic or something similar so you know exactly what is happening in the root area. Also, remember to use stakes to avoid damage from strong winds.

Philosopher Seeds
Amnesika 2.0 grown outdoors with coco coir

If you have any doubt or comment in regard with coco coir, please leave a comment here and we’ll be pleased to reply it!

All our best vibes!

Comments in “How to grow marihuana with coco coir” (4)


herb 2022-06-17
Hey i have a question about how to work with the runoff ec/ph in coco coir. I have always a low runoff ph between 4.5-5.1, what could be the cause for this problem? I tried flushing the plants and it doesnt change the ph of the coco. I did a 1/1,5 extraction method - 100ml ro water and then coco coir filled to the 250ml mark, steer it and let it sit for some hours - the ph was the same as the runoff ph because it should give me more accurate readings what is happening in the rootzone. Do you know what could maybe cause this low ph ? The only thing i think is, it is caused by some pathogens in the rootzone. How do you work with ec/ph runoff when growing in coco coir? I tried to find any informations about this problem and the only thing i found was that pathogens/root rot would cause this problem.

Philosopher seeds Staff

Tim 2022-07-08
Hi, thanks for your comment and question. Rather than root pathogens, I imagine that the problem could be caused by accumulated salt residue in the coco leading to a low runoff pH. This can happen if you're watering with small amounts each time or leaving the coco to get too dry between waterings. Aim for the humidity of the coco to fluctuate between 70% and 40% and aim to get at least 10% runoff with each watering, which ought to prevent any buildup of salts affecting the runoff pH. The frequency and amount of irrigation will depend on several factors like the size of the container and the size and life stage of the plant itself. The regular use of enzyme products in irrigation can be a big help in preventing salt residues too. I hope that helps solve the issue. Best wishes!


Uk 2021-09-02
Hi what feed schedule do you use? What neutrients and boosters? By the way really good explanation to grow in coco.

Philosopher seeds Staff

Tim 2021-09-02
Hi and thanks for your comment. We like to combine BioBizz Coco Mix substrate with the BioBizz range of organic nutrients and boosters. Another nutrient brand that we can recommend is BAC who do a great range of nutrients specifically aimed at coco growers. As for the feeding schedule, we prefer to use the charts provided by the manufacturer at first, then adjusting the amounts to get the best results from the plants once we see how they react. I hope that helps, best wishes!


Marko Stevo 2019-02-12
Hi everyone.iv got a question im growing in coco oudoors in pots and my ph is at 6.3 to 6.8 and it loves it b4 that used to be realy yellow and thin stems after the adgasmemts to that range it's green as growing left right and centre.why is this loving so high range then 5.5 to 6??


Charlotte S. McCluskey 2018-08-10
Do you know you can buy the coco coir already in grow strips for cannabis cultivation? Or grow bags of all sizes ready to set into trays? They can be customized to any dimentions and arrive ready to hydrate and plant

Philosopher seeds Staff

Dani 2018-08-10
Hi Charlotte, You can try here. Best!

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