In recent years a new growing medium became extremely popular among gardeners: coconut coir. What is it, why is it getting so established, and why should you use it?
Coconut coir is obtained by processing the coconut husk’s inner layer, a mass of thin fibers and small size, dust-like, pieces of material. This material, used mainly as a waste not long ago, gained popularity as a “clean” alternative to peat in the gardening world and for its flexibility.
Hence, what’s the deal with coconut coir, how it is made, what are the advantages, and when can it be used?
Coconut coir is obtained by processing the internal hairy layer of the coconut husk. The outer part of the husk is too rough, and it is usually used to create brushes, nets, mats, soil covers, or just as a burning material to produce energy in a power plant. The internal layer, with those thin air and dust-like particles, are the ones from which the excellent quality coco coir is made and used by gardeners all over the world.
One of the best coco coir commercially available is the Plantonix shown below. As we will discuss below, it has all the advantages of the top quality coco coir to help to promote growth. However, check more how to use it (cannot be used as soil on its own)
Interesting enough, coconuts are fruit like the apples rather than nuts. The coconut shell (that woody clean and smooth you buy at the supermarket) has already been cleaned by its outer layer called the husk. This husk is made of rough, brown fiber-like material and is smaller, very short threads of around 0.04 inch long made of a substance that is a mix between wood and a leaf, as discussed in this study.
Previously we discussed the environmental benefits of coco coir. Is coco coir an environmental blessing then? No. This is related to how coco coir is produced.
As discussed by the philippine department of agriculture (Philippine is the second top country after Indonesia for the production of coco coir) and the FAO detail discusses the process here summarised:
- Extraction: the husk is separated by the nut. This can be done through machines although often, is done manually;
- Soaking: this is a long process that lasts up to a year to get rid of the salt. Indeed, as coconuts are grown in their natural (close to the sea) environment, they can get really salty. This process also allows bacteria in the water to operate making the fibers easy to process;
- Cleaning: fibers are extracted by hand, washed, and dried. A further manual process is required to lose the fibers;
- Drying: it is not merely leaving the coconut coir to dry in the open air. Indeed, the main coco coir producer countries are also those with the most torrential tropical rains and high humidity. Hence, no surprise that drum drying is used. This is essentially a hot drum that rotates in which the pit is placed in;
- Shipment: this is one of the most underrated points of the coco coir production. The number two countries producing the raw material for coco coir are in the Asia area. This implies long travel on cargo to arrive in the EU or even further in the USA;
- Compression: coconut coir comes in convenient blocks. These are produced by compressing machines and, often, assembled by the manufacturer locally.
Below you can check a video showing some of the steps discussed above. To note that what discussed above is not the only way to produce coconut coir but a quick summary of the most adopted processes.
Hence, you now know that coco coir is not the perfect environmental-friendly product you might have thought at first as:
- It requires intense manual labor undertaken mainly by women in underdeveloped countries;
- The workers in coco-coir factories are exposed to high concentrations of dust. Even though research has found no correlation with workers’ respiratory issues in coco-coir factories, breathing inert dust for hours, even if not harmful, is not one of the best working conditions (workers do not wear a mask);
- It does involve an important transport system as coconut production is not typical of the USA or the EU.
Coco coir became extremely popular last year, becoming the stronger contender of peat moss and, in general, as a growing medium (even for more advanced applications as hydroponic). Hence, what are these advantages compared to peat?
The main reason justifying the adoption of coco coir is to be used as an environmentally friendly replacement of peat moss. Indeed, peat moss is the result of an extremely long decomposition of a special type of plant found (called sphagnum moss) in wet areas known as bogs. In many countries around the world, the rate of extraction is much higher than that by which peat is naturally created . In simple words, in such areas, peat is going to exhaust very soon.
Moreover, the presence of peatlands (bogs) is important as a natural carbon capture system and their water filtration and regulation capability, as discussed in this study. Extracting peat moss is likely to reduce or remove such peatlands and all the benefits mentioned above.
Coco coir, on the other hand, is a bioproduct of the coconut industry that does not affect the environment as peat moss was shown to do. Indeed, coconuts are produced for food consumption and oil production, and the husk (from which the coco coir is produced) comes with it.
However, as discussed above, coconut coir has an impact on the environment and the working conditions of the people who produce it in third-world countries.
Is the coco coir production worse than peat moss? Here my point of view.
It is extremely hard to tell. You have a finite (or slow producing material) resource such as peat moss. In contrast, coco coir is a waste product that, despite being abundant and, ideally limitless, requires more processing, human labor than peat.
Here my personal view.
In areas of the world where peat is limited (like in the UK, for instance), coco coir is a better alternative. In those (few) areas with a large peatland where the rate of extraction is lower than the rate by which peat is regenerated, I would opt for peat moss.
Check the case of Canada, for instance. In this case, the main concern about the finite amount of peat does not apply as only 0.03% of Canadian peatland has been used for peat production. Hence, here, peat might be a better option as it also avoids the massive transport required for coco coir.
Coco coir is compressed in dry rectangular bricks. This presents two important advantages over peat moss:
- Volume: this allows having a large amount of material in a small space. Indeed, water uses a massive amount of space in those growing mediums (like compost, for instance, or peat moss) that contain them. This allows to transport more in the same space (less carbon emission);
- Rectangle: it is very easy to transport effectively something that can be piled up. This saves space, reducing the carbon emitted during transport;
- Weight: The lack of water also has the advantage of reducing weight. Important? Yes, as this also reduces the fuel consumption (both via ship cargo and trucks)
This is a controversial argument against the coco coir. Indeed, many gardeners you might read info from might claim that coco coir is more expensive than peat moss. This was true a few years back when coco coir was still something new, and the market was still at its infancy. However, nowadays, the coco coir’s price per pound (kg) is comparable if not cheaper than peat moss.
Moreover, do not forget that coconut coir sold as a brick is almost totally dry and when watered expands many times. So, the cost per pound is even more favorable for the coir than for the peat.
Coco coir is known for its antifungal properties. This is also confirmed by a few studies such as this one where soil pathogens where repressed from developing. More precisely, mycelial (well-known fungi that create spider-like white webs on top of the soil).
Coco coir inhibited mycelial growth of various soilborne pathogens by up to 75%University of California
On top of such suppressive properties, how coco husk is processed to produce coco coir (through soaking and cleaning) reduces the chances dramatically to have fungi spores and harmful bacteria when compared to peat.
This is extremely important when growing indoor plants, where usually more damp conditions, attract a large variety of pests.
Mold can develop on pure coco coir medium, although with way less frequency (as discussed above) than other growing mediums. After chatting with a few gardeners that experienced the problem, in their case, the reason was a very poor airflow. Indeed, to grow seedling airflow is important for two reasons: 1) make the stem stronger and less floppy, 2) allow better aeration preventing mold and fungi formation.
In case the mold on the coco coir is the white, often close to the edges (as more moist), it is very likely to be a Saprophytic fungus. This is not harmful to the soil or the plant itself, so nothing to be worried about. If you want to get rid of it, just let the coir dry and rub it off with your hands or any tool.
Is coco coir acidic or pH neutral? Good quality coco coir (as this one on Amazon) is pH neutral (around 5.9 and 6.5 generally). However, be careful, this is not always the case. If you buy cheap coco coir, chances are that it will be acidic. Why?
Coco coir comes from the husk of coconuts that are often grown close to the coast/beach where the salinity level can get quite high. This, in turn, makes the husk of the coconut naturally acidic. That’s one reason why coco coir manufacturers need to soak and clean the husks (discussed before on the section “how coco coir is made”).
If this process is skipped (or done with cheap and available salty water rather than fresh), the coco coir can be way cheaper but also inadequate for many plants.
Is the pH neutral of coco coir an advantage compared to peat moss? Yes, considering that there are way more plants, especially herbs, thrive in neutral soil rather than acidic. Hence, chances are that you need a pH neutral soil. Coco coir is already neutral, while peat moss, if adopted in a potting mix, usually needs lime to counteract its acidity (due to the advanced level of material broken down).
Coco coir is a great material that I do use often. However, it is important to know that it comes with some drawbacks (although nothing major).
The difference between peat moss and coco coir in retaining water is significant. Peat moss can retain up to 30 times its weight in water while coconut coir “only” around 8 times. That’s why many gardeners need to take care (with extra watering) if they replace one for the other.
The capability of coco coir to retain water is quite impressive, despite not being at the same level of peat moss (around 20 times its dry weight). This is one of the main features that made coco coir an attractive replacement of peat moss after its environmental friendliness.
This is because, among the materials used to make a great potting soil or starter mix, it is important to have at least one of them able to effectively retain water. That’s also why it is very hard to grow anything in the sand (due to its high drainage).
What is the coco coir to water ratio?
When you buy coco coir, as discussed above, it comes in a brick form. However, coco coir cannot be used straight away in this brick form. You need to water it. How much? Well, given that it absorbs around 8 times its volume in water, you need an 8:1 water to coco coir ratio.
How to water the coco coir brick?
Place the brick inside a large bucket. Pour a large amount of water (but way less than 8 times the volume of your brick) on top of the brick and let it sit until the water is absorbed. When you see that all the water is gone, but the brick looks still kind of compact and half dry, flush some more water again. Repeat until you have a fluffy and broken down medium.
That’s what I do, so you avoid overwatering the coco coir as it might get difficult to get the excess water out if you pour a massive amount from the beginning.
Trick: after the first watering tries to break down the brick with your hand or a tool. This will accelerate the absorption of water. For more, check the video below (starting from minute 3 as the guy talks a lot).
Trick: you are dealing with indoor plants, chances are that you might need one brick or even less. In this case, do not soak the whole brick. Take a good knife (a bread knife is ideal) and chop away the part of the coco coir you are not going to use. This will avoid wasting.
Coco coir is classified as an inert material; hence, it is no surprise that many gardeners blame its low nutrient content. However, the low nutrient content of coco coir is not a disadvantage compared to peat moss, as shown in the table below:
Nutrition-wise coco coir is famous for being more abundant in potassium (6 times more than nitrogen). However, this is not as good as it might sound.
Indeed, an excess of coco coir can cause excess potassium. Why?
Coco coir is a chemical magnet that attracts calcium and magnesium very strongly. So those micronutrients (as also in lower content into the soil than the main ones) might be subtracted to your plants, causing potassium or/and magnesium deficiency whose symptoms are discussed in this study.
Hence, is coco peat a fertilizer?
Coco peat cannot be used as fertilizer because, differently from a fertilizer, its nutrient content is so low that its benefits to the nutrient profile of the soil to which it is added are minimal. Moreover, coco coir manufacturers do not specify its nutrient content (NPK) as it is not meant to be used as fertilizer.
A fertilizer is a chemical (either organic or artificially produced) that provides a high concentration of nutrients in a low volume. Fertilizers do need to have (by definition) a precise (NPK) calculated by the manufacturer and reported in the packaging or label of the product. This is not the case for coco coir.
Can You Use Coco Coir Instead of Soil?
Coco peat should not be used instead of soil to grow plants and herbs. This is because of its low nutrient content, high water retaining capability. Indeed, if not for a few exceptions, it cannot provide the number of nitrogen plants that need to thrive. It can get too soggy if not watered with extreme care and, over time, as a base on material closely related to wood, tends to decay.
Here the info for the pro.
Although I do not recommend growing a plant entirely (or almost) in coco peat, especially if you are a beginner, it is still possible to do so. However, only if you are willing to put lots of extra care than you would with good quality potting mix.
To grow a plant entirely in coco coir, you need to compensate for what is missing in a good and balanced potting mix, mainly nutrients, and drainage. Hence, you might have 1) to provide fertilizer regularly and 2) add a second growing medium (such as perlite, another inert and almost zero-nutrient material) to increase drainage to avoid root rot.
However, even if you follow the above instructions, your plant growth will be stunted, developing fewer leaves (smaller and yellow in color). Below an experiment showing how the coco coir based tomato managed to produce tomatoes despite being weaker and unhealthier.
Coco coir can be used as a potting mix component, seed starting medium, in hydroponic, as a mulch, and in a compost pile.
Using coco coir as part of a balanced potting mix is by far the most common application for this material. It is advised to not use more than a third of the potting mix weight in coco coir as it can become a too soggy medium.
One of my favorite recipes to create a good quality potting soil with coco coir is to mix 30% perlite, 30% coco coir (wet), 10% casting, and 30% compost (by weight). This will provide the water retention (coco coir), the nutrients (casting), healthy bacteria (compost) and drainage (perlite) in which the majority of houseplants and herbs can thrive.
Coco coir is a great medium for seed starting. As discussed in the detailed seedling start guide, a good seed starting medium should be:
- Sterile to reduce fungi formation, otherwise very likely to appear and affect the seedling development given the high moist level and temperature required;
- Retain water: this because seedlings require a consistent moist medium to emerge;
Moreover, if the medium is used only for seed starter, nutrients are not necessary as the seeds contain everything it needs to develop the first roots, stems, and pair of fake leaves.
Coco coir tick all the boxes to be an ideal seed starter mix. I use it often to grow microgreen (chia among my favorite). Research also demonstrated the ability of a pure coco coir mixture to promote seed germination.
Coco coir is widely used as a hydroponic medium due to its ability to hold water.
However, despite not being an expert in hydroponic, I would use nutrients specifically designed for coco coir medium. Why?
As discussed above, the potassium content in coco coir makes it a chemical magnet for calcium. Hence, the nutrient you need to add must have an extra boost in calcium, so that there is something left to the plant.
This means that, due to the potassium presence in coco coir, the hydroponic liquid nutrient should have a higher concentration of calcium. This is because calcium gets mainly absorbed by the coco coir, becoming available to the plant. Here is a good one on Amazon.
Coco coir is compostable. Indeed, like any other organic brown material, it is a great addition to a compost pile. Many gardeners use their leftover coco coir (for instance, after using it as a seedling mix) and throw it (still wet) in the compost pile. It absorbs pockets of water that prevent oxygen exchange (essential to maintain a healthy compost and avoid anaerobic bacteria to take over) without letting the mixture dry (as it holds it). It helps suppress odor and does not attract pests, as many other materials do.
If you use out of the package coco coir, take the time to soak it in water and, only once fully expand, you can place it in the compost pile.
Such terminology is widely used in gardening, and to be honest, I was quite confused for a while. Here then the difference;
Coco pith, peat, coir: these are three different ways to indicate the same thing. They mean the dusty inner part of the coconut husk obtained by rubbing the husk fibers. Coco coir is a term widely used in the USA, while coco peat is more common in other areas of the world such as India. Coco pith is a more specific name for it.
Coco fiber is the fiber that makes most of the coconut husk from which, by mechanical action, the coco pith/peat/coir is extracted.
Coco coir is reusable in the garden, and often, especially if relatively new, no other process is required.
If the coco coir is old (a few months to a year) and got totally dry, you just need to place it on a rinse with large holes if possible, and then you water it (tap water is fine). The rinse is a good idea to let the coco coir dust (coming from the breaking down of the larger fiber) to flow away. Once, the water coming out from the rinse is decently clean, just place the coco coir in a buck and repeat until all your old coco is clean. If possible, also remove any large branch that might still be there.
This process is not necessary if you just used your coco for microgreens, and, after a week or so, you want to use it again for a new batch of microgreens. Just water it again, remove some small chunk of plants that might be left and repeat.
Another, even easier way to deal with coco coir, as discussed above, is to throw it in the compost pile as it does improve the composting process, especially if the compost pile has an excess of water.
Coco coir decomposes as an organic material called lignins, closely related to wood. However, it is worth noting that due to its high carbon to nitrogen ratio, and cellulose content, it tends to degrade very slowly, as discussed in this study.
Fungus gnats can develop in coco coir as well. Many gardeners experienced such problems, especially using coco coir as a starter mix where temperature and moisture need to be kept high. For more information, check the guide on how to remove fungus gnats.
Here the most critical takeaways in your choice between coco coir and peat and, more importantly, to understand the characteristics of this great growing medium.
- Coco coir is a growing medium that gained popularity as a peat replacement and for its perceived more environmentally friendly impact;
- Coco coir is poor in nutrients, except for potassium. This can be a problem for the absorption of calcium. In hydroponic a liquid solution designed for coco coir should be chosen;
- Transport, price, pH, antifungal properties, and flexibility in use are the most known features of coco coir.
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