Coco coir has become a staple on my balcony. I seriously have to thank like 90% of my harvests in total to that awesome inert growing medium!

A few years ago, I hated this stuff. All plants I put in there died and it got stanky really quick. Fail.

Then, I figured out that these cheap bricks have a lot of junk in there that needs to be flushed out. In particular, high amounts of sodium (nearby sea water), which can be toxic even in small amounts for plants.

But also, there's one even bigger threat: cation exchange. Coco coir wants ALL the calcium and magnesium it can find. So it steals it from your plant.

Even worse is, that it gives off LOTS of potassium (and sodium) in exchange, completely massacring the plant.

BONUS: The roots will suffocate too. Coir absorbs water TOO well.

Despite learning all of that, I found it to be the most versatile, cheap, and easy growing medium ever. It just needs a few steps of preparation.

Preparing the buffering solution

Create a double strength nutrient solution, containing calcium and magnesium. You could use only CalMag too if you have it around.

I also added some silicate.

Dissolve 10 l in a bucket.

Brick

Enclose the coco coir brick in a washing bag for bras. The ones with a zip tie.

And throw it into the bucket.

It will expand to 10 l in the next minutes, soaking up most of the solution.

The EC climbed to 6 mS! More than the nutrient solution provided.

Now, let it soak over night. And knead it like bread dough a few times if you want 🙂

Add some perlite

Drain it by lifting the bag out. Add 1 l (10% by volume).

Flush

Press out the bag and add 10 l of osmosis or rain water.

Let it soak a few hours, moving it sometimes.

Measure the EC.

Repeat.

500 mS in the second flush. Would be good enough for growing big crops like chili or weed.

I, however, want the good stuff. Seedlings could develop badly for example.

It also still looks filthy, and these microparticles allow less aeration.

Third flush.

This is great now. I use it on sensitive seedlings without issues.

Dry it

Place the bag somewhere outside to dry. Some rain showers on top are great. But it should be dry in a few days when hot.

Result

Coco can hold immense amounts of water.

If you now add between 10-30% perlite it can even stand in nutrient solution for days without root rot, while still holding to moisture.

The now "modified" media is now almost completely inert (no more nutrient stealing issues) and pretty much can't decompose, even when constantly moist.

It's ultra cheap (1€/ brick for 15 l of substrate) and also sustainable, while being "disposable" at the same time. Even better when you mix it into your garden compost after hydro use for airy moisture retentive soil.

I fucking love this stuff!