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Tips for Growing Autoflowers in Coco Coir

Coco, how to use it and tips for making your own mixes.
15 June 2022
7 min read
Tips for Growing Autoflowers in Coco Coir

  • 1. The qualities of coco coir
  • 2. What types of coco i can find?
  • 2. a. Coco in a brick
  • 2. b. Loose coco
  • 3. Choosing the right type: inert or amended
  • 3. a. Inert coco
  • 3. b. Amended coco
  • 4. Different types of additives
  • 4. a. Perlite
  • 4. b. Soil
  • 5. Watering and feeding
  • 6. Different medium mixes
  • 7. In conclusion

Coco coir (also known as coco fiber) is an organic medium extracted from the outer layer of coconuts, it is primarily known for absorbing and retaining water better than any other medium, you can find it pre-mixed with nutrients or amend it yourself, mix it with additives (like perlite or soil). To help you choose what suits you the best, we've separated a couple of tips.

Coco-coir is quickly becoming a favorite medium among both novice and experienced growers alike. It is a forgiving medium, and thanks to the fact that it is a soil-like substrate that can be controlled in a similar way to a pure hydro set up in terms of nutrient selection and dosing, it offers most of the advantages of both soil and hydro combined while cutting down on many of the cons. 

In many ways, it is also the most budget and eco-friendly substrate currently available for cannabis cultivation, so let’s jump in and see why almost everyone is in love with coco-coir!

1. The Qualities of Coco Coir

Coco is a very good medium to use, thanks to it being fibrous and strong, it resists weathering, can be reused, holds onto water and nutrients and has a light texture, so it provides a good amount of oxygen to the roots.

2. What Types of Coco I Can Find?

Coco may come in loose fibers or compressed in a brick, quality is usually the same although sometimes depending on the brand it may be stronger or more brittle.

Coco in a Brick

Usually, people buying coco fiber in a brick are looking to save space and a couple of bucks. It's cheaper because you have a bit of work before using it and it saves up space because it comes compressed into a brick.

Tips for Growing Autoflowers in Coco Coir: coco in a brick

Compressed coco coir in a brick will make you work a bit harder but it's cheaper.


We recommend to bake it in the oven for a minimum of 4hs (up to 6hs) at 95 Celsius (203F) to kill any bug eggs left in it.

After letting it cool down, you have to immerse the whole brick in a big tub of water (25L, about 6.6 gal), you can use a mix of water and 10% bleach, but if you already used the oven technique, it may be an overkill.

Loose Coco

With loose coco you'll spend a little bit more but you can skip the oven, it's ready to use out the bag.


Tips for Growing Autoflowers in Coco Coir: Loose Coco

Loose coco ready to be used right out the bag.

If you can't find a good brand and you want to be 100% sure it's clean, you could do the following:


Rinse coco to remove dust, if you suspect there are bugs in it, you can leave the fibers for a couple of hours in a tub with a mix of water and 10% bleach, it's important to rinse them thoroughly with water only and then let them dry overnight, you don't want to hurt your plants with any bleach left.

These days though, almost every single reputable nutrient brand is producing their own coco-coir mix available for use straight out of the bag. We recommend CANNA Coco Professional Plus (available in a loose or compact form - we like the loose form better), Roots Organics Coco Soilless Mix,  FoxFarm Coco Loco, and Mother Earth Coco Mix. 

3. Choosing the Right Type: Inert or Amended

Inert Coco

Coco coir mostly comes inert, which means it does not have any nutrients in it, although you can find a wide variety of amended coco, and it definitely will ease your work, it comes pre-mixed so you cannot control the quantities and will not always be the best choice.

Amended Coco

If you're going to use amended coco we recommend testing it before or go for a low level of NPK and feed after if you see your plant is getting hungry.

For best results, you should buy inert fiber and mix with a powder nutrient mix of your choice, this way you can control the quantity of every single nutrient your plant will have access to.


Tips for Growing Autoflowers in Coco Coir: Amending Inert Coco

Amending inert coco with fiber and a powder nutrient mix.

We recommend organic feeding, you'll have a happier plant with an overall better harvest, generally producing more terpenes. You will taste the difference!

Always keep in mind that you will have to adjust the quantities to be used with your autoflower. Nutrients generally come with instructions to be used with photoperiods. An excess of inorganic nutrients in the medium can burn the plant (compromising your harvest) or end up killing it.

An excess of organic nutrients will not kill your plant but you'll be spending way more than you should.

4. Different Types Of Additives

Before talking about additives, we need to talk about our climate. Being indoors or outdoor, our relative humidity should be around 60% and temperatures should be between 20 - 25 degrees Celsius (around 68 - 75 F). Obviously, that's a general rule and may depend from strain to strain.

Tips for Growing Autoflowers in Coco Coir: Perfect Conditions to grow cannabis

Make sure you have perfect conditions for your plants.

If our climate is not good enough we could have problems like our medium drying too quickly, holding too much water or roots not receiving enough oxygen. To achieve a good mix, we should learn about the qualities and characteristics of additives. A perfect medium should be fluffy enough for the roots to get oxygen but also hold a good amount of water.


To have 100% clean additives, we recommend rinsing with water and letting dry before using. 


Perlite is the small balls made mostly of silicon that is commonly found in many different potting and soil premixes found in all gardening stores. It is porous and should be used if you are watering too much, they'll help protect you against mold and will keep the medium oxygenated. Almost every single coco-coir mix will have perlite available in it, with many using a 70% coco-coir 30% perlite ratio. 

Tips for Growing Autoflowers in Coco Coir: Perlite

Perlite protects your plant against mold and keeps your medium oxygenated.


Perlite can be washed and reused for several harvests.


Soil + coco is usually mixed when you want to use pre-amended soil but need to hold more moisture. We recommend a mix of 50/50 soil to coco and adjust according to your preferences. You can mix amended soil or inert, also can mix your own mix of powdered nutrients to the inert soil of your preference.

5. Watering and Feeding   

When watering coco, you should never let it dry out, try to keep the medium always slightly wet or at least damp. There are some situations where this statement is not 100% correct though. Many cultivators like to let the medium (whether that be coco-coir or soil) totally dry out once a week to promote vigorous root development. Think about it, if the roots are constantly supplied with the perfect amount of water then there is no use in them searching energetically for a new source, right? By depriving the root zone of water on the odd occasion, you can help that root ball develop into a monster. This sort of root training should only be done during the vegetative growth stage though, as the plant needs all the care it can get during the flower production stage. 

When using a drip feeding irrigation system you’ll need to water up to 4 times a day in coco, depending on the climate and the stage the plant is in. When feeding inorganic, mix nutes with water, adjust pH and water.

If you’re using a top dressing or you already mixed nutrients in the medium just water, you don’t need to feed unless the plant is hungry.  With organic feeding you don’t need to adjust pH, just mix nutes and water normally, if you’re using a top dressing or already have nutes mixed in soil only feed if the plant is hungry.

If you are hand watering then once a day is fine, but always remember to water or feed until you see a decent amount of runoff. This will ensure that there will be no buildup of nutrients in the medium, which is the leading cause of a nutrient lockout. 


Try to use osmosis water or at least filtered water when feeding inorganic to you autoflower.

6. Different Medium Mixes

Here we leave a couple of recipes for different cases:

•  General mix recipe: 30% coco, 20% perlite and 50% soil or 80% coco to 20% perlite. 

•  For a well-drained medium: 70% soil to 30% perlite.


Tips for Growing Autoflowers in Coco Coir: Coco Coir Recipes

Obs: Different recipes will affect how often you have to water your plants.

  • For a well-aerated medium: 80% coco to 20% perlite.
  • If your soil is drying too quickly: 70% soil to 30% coco.

If this is a little confusing then just go for about 70% coco-coir to 30% perlite. This will cover most bases in most cases, and there’s no need to overthink this aspect too much, especially if you are new to cannabis cultivation. Remember to always add a decent layer of clay balls at the bottom of the pot to help with drainage, and to add an extra drainage hole or 10. Most store-bought plastic pots only come with a couple of drainage holes but trust us when we say the more the better.

3. In Conclusion

You need to remember not all plants are the same, there can be variations even in plants of the same strain. We recommend knowing each individual plant to deliver the optimal mix of nutrients and soil but like everything, there are exceptions.

Sometimes you’ll find plants that do well without nutrients, that’s the case of our Purple Lemonade, a cross between Purple and our citrus Cali genetics. 

Purple Lemonade Auto
5 out of 5
I can’t wipe the grin off my face. Too soon to comment on the smoke as it needs more curing but at least it’s knockout potent.
Verified customer
Reviewed 5 October

This autoflower will do exceptionally well without nutrients but will perform exquisitely with good quality nutrients and proper feeding. 

15 June 2022