Properly preparing and buffering your coco coir ensures that you are growing in the best possible medium for your plants. This tutorial walks you through the process of selecting, preparing and buffering coco coir. We review the options you have for selecting pre-buffered coco coir products or purchasing a dehydrated coco coir brick. Brick coco is far cheaper and easier to ship but it requires that you learn how to buffer coco coir for yourself. We provide step-by-step instructions for how to buffer coco coir and provide guidelines for the best coco/perlite ratios in different container sizes. We also provide a video of the complete rinsing and buffering process.
In this Tutorial:
Recommended Coco Coir Products
When purchasing new coco coir, you have many options. You can get a cheap brick of dehydrated coco, or a relatively expensive, already prepared product. Pre-buffered products are available that allow you to skip the steps for rinsing and buffering. You simply rehydrate the coco and add your perlite. However, these products are expensive to purchase and ship. Brick coco is very economical, but it does require some work to buffer it as we describe below. In either case, the quality of the final product will be the same. Purchasing a prepared product is the equivalent of hiring someone to do the rinsing and buffering for you.
Pre-Buffered Coco Products
There are two options for pre-buffered coco products which we have experience with and can endorse.
Both the Canna and Roots Organics products are pre-rinsed and pre-buffered. They come in bags with fibers that are dehydrated, but not compressed. The Canna Organic Substrate contains 50 liters which enough coco for four 5-gallon pots. The Roots Organics Cocopalms contains 42 liters which is more than enough for three 5-gallon pots.
To prepare these products for use, you need to simply rehydrate them and mix with perlite. You may use tap or bottled/filtered water to rehydrate. Once rehydrated you need to mix with perlite and verify EC as described below, but you can skip the rinsing and buffering process.
Dehydrated Brick Coco Products
There are numerous products available online for dehydrated coco bricks. All compressed bricks of coco should be rinsed and buffered before use regardless of the brand or claims on the packaging. If you follow the instructions below you can transform any brick of coco into a superior growing medium for cannabis. However, some bricks provide a better product to begin with and you end up with more quality coco fibers in the end. I recommend the Plantonix Organic Coco Bliss. It is an excellent deal and after rinsing and buffering it becomes a very high quality coco product. Each brick is ten pounds, which produces more than enough coco for six 5-gallon containers.
Perlite to Mix with Coco
Regardless of the type of coco that you start with, perlite is critical to help with drainage. Almost any perlite will do, but this 18 quart bag from Hoffman Horticultural is lightweight and natural. It has a good mix of particle sizes, which help to improve drainage and aeration.
Preparing Coco Coir for Cannabis
There are many reasons that coco is a superior growing medium for cannabis: it has excellent water retention and drainage properties, offers abundant root space, and, if buffered, it will not interfere with plant nutrition. These features of coco enable the style of high frequency fertigation that we recommend (See “How to Grow Cannabis in Coco Coir: Principles of Fertigation”).
However, if you purchase a brick of coco and you do not rinse and buffer it, you are not growing in a superior medium. Un-rinsed coco is laden with “coco peat”, which are small dust sized particles. The coco peat does not retain air like the larger coco fibers do and as a result, you can run into problems with drowning your roots if you grow in coco with a lot of coco peat.
Buffering is an even larger issue! Coco must be buffered with calcium (Ca) and Magnesium (Mg) before it becomes a superior growing media.
Why You Need to Buffer Coco Coir
There are cation exchange sites in coco that will interfere with nutrition until they are buffered. The cation exchange sites in coco naturally come loaded with sodium (Na) and potassium (K) cations. However, the Na and the K are only weakly held to the exchange sites. In the presence of calcium (Ca) or magnesium (Mg), the sites will release their Na or K cations and lock onto the Ca or Mg. These processes are known as “cation exchanges”.
Buffering coco is accomplished by soaking it in Ca and Mg. This allows the cation exchanges to take place prior to adding plants. Simply soak your coco in a solution of Cal/Mag water and the exchange sites will release their K and Na cations and lock onto the Ca and Mg. When the cation exchange sites bond with Ca and Mg rather than Na and K, it is “buffered”. The bonds that hold the Ca and Mg to the sites are very strong and cation exchange will largely stop. This means that all of the nutrients that you add to the water will be available to the plant at the ratios that you provide them.
Growing in Un-Buffered Coco
Many growers are unaware of the need to buffer the coco and they try to grow plants in unbuffered coco. In unbuffered coco, the cation exchange sites will strip the nutrient solution of the Ca and Mg and replace those cations with Na and K. This creates a sub-optimal Nutrient Element Ratio (NER) and renders Ca and Mg unavailable to the plant.
Failing to buffer the coco is why so many growers suffer calcium deficiencies in coco grows. Manufacturers of prepared coco products try to exploit these problems and convince growers that only their proprietary products are suitable for growing. However, it is actually very simple to properly buffer your coco yourself. This tutorial walks you through the process and provides all the information you need to turn even the cheapest brick of dehydrated coco into a superior growing medium.
How to Prepare and Buffer Brick Coco Coir
Rehydrate and Rinse
When starting with a dehydrated brick of coco, it should first be rehydrated in tap water. Rehydration is fast as coco loves to absorb water. The slurry that is produced should then be rinsed over a screen to remove the finest coco particles, known as “coco peat”, which retain too much water. Your goal at this stage is ending up with larger coco fibers. Use a 1/8” mesh screen or a perforated strainer. I use a perforated strainer which you can see me doing in the video above. This is my new strainer, which is perfect for rinsing coco. It is not the strainer I used in the video.
Buffer Coco to Satisfy the Cation Exchange Sites
After rinsing the coco, you need to buffer it prior to use. I recommend double buffering, which ensures that the cation exchange sites are fully satisfied with Ca and Mg. After buffering, cation exchange will no longer interfere with your grow and the plants will take nutrition (including Ca and Mg) directly from the nutrient solution.
To Double-Buffer Coco:
- Prepare buffering solution:
- Tap water may be used for buffering solution
- Add at least 7.5 ml/Gal of General Hydroponics CaliMagic
- Electrical Conductivity (EC) of the buffering solution should be 1200-2000
- pH of the buffering solution should be greater than 6.2
- Place coco in a fabric pot - and then place that into a 5-gallon bucket
- Soak coco completely submerged in buffering solution for 8+ hours
- Raise fabric pot and allow to drain - dump bucket
- Soak again completely submerged in fresh buffering solution for 8+ hours
- Drain and it is ready to be mixed with perlite
Mixing Coco with Perlite
Perlite dramatically improves water drainage and aeration in coco. Mixing perlite at the ratios given in the chart below makes it very difficult (but not impossible) to overwater. Also, since it improves water flow through the medium it improves the flushing of unwanted salts. Coco without perlite does not drain as well. However, in small containers, drainage is better, and you can reduce the perlite percentage to increase root space. When following a transplant strategy, perlite percentage should be mixed at ratios needed for final containers.
Coco Perlite Recipes:
|Container Size||Quantity of Media||Perlite %||Perlite Volume||Coco Dry Weight|
|2-gallon||2 gallons||0-20%||0-1 quart||450g|
|3-gallon||3 gallons||30%||2 quarts||550g|
|5-gallon||4 gallons||40%||4 quarts||650g|
|7-gallon||5.5 gallons||50%||6 quarts||800g|
|10-gallon||8 gallons||50%||9 quarts||1250g|
Once buffered and mixed with perlite, coco is an unbeatable grow medium for cannabis!
Verify Electrical Conductivity (EC) Prior to Adding Plants
Before adding seedlings or plants to your coco/perlite mix, you should always verify that the EC is in the appropriate range for their stage of growth. Since the buffering solution is high EC, you may need to rinse the coco with plain water prior to adding plants. Seedlings in particular are vulnerable to being burned by the residual EC in the coco remaining after the buffering process.
Fill the container you will be using with coco/perlite and add water slowly until you can collect run-off. Measure the EC of the first run-off water to leave the pot and confirm that it is in the appropriate range for seedlings (less than 400 or 0.4 EC) or vegetating plants (less than 1000 or 1.0 EC). If the EC is high, continue pouring plain water through the pot until run-off readings are in the appropriate range. After rinsing the EC down like this, it is a good practice to then fertigate (add water with fertilizers) at the appropriate EC prior to adding plants.
If you are unfamiliar with EC or unsure why or how to measure it. Be sure to read our article, “Understanding Osmosis and EC”. Managing EC is easy and meters to measure EC are cheap. Measuring EC allows you to manage your coco grow like a pro!
Growing in Coco Coir
Once you have prepared and buffered your coco, you are set to begin. To take full advantage of the miraculous growing properties of coco coir be sure to read our articles and tutorials on Growing in Coco!
About Our Product Recommendations
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