This article is for coco coir that is not labeled as “buffered.” If your coco coir is already labeled as buffered, skip everything below and plant away. Otherwise, read on! It is best to assume any coco coir without a label is unbuffered. Don’t fall for the label “washed,” as this is not the same and buffering is still needed.
At Richmond Hydroponics, we love coco coir. It’s affordable, sustainable, mostly inert, and – paired with perlite or rice hulls – holds the perfect amount of water while also draining well for all growth stages. The problem is with the words “mostly inert.” In its natural state, coco coir contains too much sodium, potassium, and various micronutrients for ideal use. This is where buffering comes in. By rinsing the coco coir with a calcium nitrate and magnesium sulfate solution, we can replace the sodium and potassium with calcium and magnesium, while the sulfates flush out unwanted micronutrients. This gives us a fresh start for an ideal grow.
What you’ll need:
- A gram scale capable of at least 1g precision. It does not need to be fancy.
- 0.14 oz or 4 grams of Magnesium Sulfate, also known as unscented epsom salt
- 0.5 oz or 14 grams of Calcium Nitrate. This will come as a powder and is different than “cal-mag”
- at least one 5 gallon bucket
- a container in which to hydrate your coco coir if it needs hydrating
- a container with drainage holes. This should be big enough to fit your hydrated coco coir. The pots that you intend to plant in will work too.
- Perlite or rice hulls. Not used for buffering, bit great for planting with.
If any of these items are difficult for you to source, we would be happy to help.
If you have a compressed block of coco coir, place it in a container large enough to hold its hydrated volume. Most labels will tell you what this volume is. If this is your first time hydrating a coco coir block, don’t worry about it too much – you’re just adding water. This can be tap, distilled, or you could even get a head start and use the buffering solution that we will prepare below. A compressed block absorbs more water than you’d think, but start out by at least covering the block and waiting until everything is absorbed. Then, if there is still dry coco coir, you can add more water. You’ll get a feel for it pretty quickly.
To prepare the buffering solution: Add 5 gallons of water to your bucket, followed the 0.14 oz (or 4 grams) of magnesium sulfate, and stir until dissolved. Now add the 0.5 oz (or 14 grams) of calcium nitrate and stir again. Depending on how much coco coir you have, you will likely need to make multiple batches. A good rule of thumb is to use 2 gallons of buffering solution for every 1 gallon of coco coir.
Next, take your hydrated coco coir and add it to the container with drainage holes. Wash the coco coir with your buffering solution. It might be easier to use a watering can for this, but you can also pour straight from the bucket so long as you pour evenly enough to cover everything. It is most effective to wash your coco coir in stages; add half your solution, let it drain, mix your coco coir around, then add the rest and allow it to drain again.
If you’re feeling particular, you can prepare more buffering solution and wash until you are content with how clear the runoff is. If you have an EC meter, knowing that the coco coir is fully buffered is as easy as measuring the solution and the runoff. When they are the same, your coco coir is buffered.
That’s it! Mix your buffered coco coir with perlite or rice hulls (we like a 3:1 or 2:1 coco:perlite ratio) and get planting!
*Many tutorials say to use “Cal-Mag.” While this works for removing sodium and potassium, it will not remove micronutrients that may be in excess. By using Calcium Nitrate and Magnesium sulfate – two molecules that can’t exist in a concentrated single part solution together (and the primary reason why fertilizers have a part A and part B) – you will get a better planting medium. If we really wanted to go all out, Disodium EDTA could be added to the buffering solution to remove even more of the micronutrients, but this is excessive and generally not even done in commercial grows.
**One reason not to be too neurotic about washing the coco coir in excess of the 2:1 gallon ratio: If you’re using our Green Grow every time you water from the start, it will act as a supplemental buffering solution and continue to remove excess sodium after the first few waterings.
Great Article!