Peat Moss vs. Coco Coir: Which Should You Use?

by Matt Gibson and Erin Marissa Russell

Coconut Coir, the widely-used hydroponic growing medium, is in recent years rising in popularity as a soil conditioner, in many cases replacing the use of peat moss, as both are very similar products. So, the question is, which one is the best for modern gardeners? This argument usually comes down to a discussion about sustainability and effectiveness. 

Sphagnum peat moss and coconut coir are both great soil additions. Both are all-natural and plant based. Both mediums help to break up heavy clay soils and improve water retention in sandy soils. Each has its own separate group of nutrients that are beneficial to the soil, and both encourage natural microbial populations. Though there are many similarities between the two mediums, they have their differences as well, and that’s where we will be better able to discern the better choice between the two. 

What Is Coir?

Coir, or coconut fiber, in its many forms, is the new kid on the block in terms of all-natural soil alternatives. Coco coir has long been used in hydroponic gardening due to its water retention and its deterrence of fungus gnats and certain diseases, as well as its root-supporting structure. Though its popularity has risen in the recent past, it functions in the garden very much like sphagnum moss.

Coco coir is a byproduct of coconut processing. The fibrous husks of coconuts are ground or decomposed in order to produce a product that is very similar to peat moss in weight and texture, but darker in color. The majority of the world’s coconut fiber comes from Sri Lanka or India.

What Is Peat Moss?

Peat moss is a traditional soilless growing medium that comes from peat bogs. Peat bogs are swamps or marshes that are filled with a decomposed sphagnum moss. Most peat moss in the United States comes from Canada. The final product is a light, fluffy, soil-like material.

Peat moss became available to gardeners in the mid-1900’s and has had a strong impact on the way we grow plants today. It has an incredible ability to manage water efficiently and hold onto nutrients that, in other mediums, tend to leach out of the soil much more quickly. In addition to these benefits, peat moss also improves the texture and consistency of the soil.

Advantages of Each

The pith of the coconut, from which coco coir is made, contains high amounts of lignin and cellulose that prevent the substance from decomposing and shrinking. This allows coir the ability to hold more water than peat moss, but it is not able to hold the water as long. Coir has a pH of 5.8 to 6.8, which is close to the neutral range enjoyed by a wide variety of plants. This means that coir is more suited to a wide variety of plants without needing the addition of limestone to adjust the acidity levels.

Peat moss soaks up to 20 times its own weight in water and releases that water very slowly. If you don’t water your plants very often, they will likely survive on the water that is stored in peat moss. While being acidic may be a disadvantage in cultivating many plants, it can be an advantage if you water your plants with tap water, which is often alkaline. Peat moss is somewhat less expensive than coco coir.

Disadvantages of Each

Cows roam freely in India, and that can be a problem for coconut coir manufacturers, as coco coir can easily be contaminated with animal manure. Fresh water is used to extract fiber from ripe coconuts. However, if the coconuts are not fully ripe, they are then processed with brine, which can cause high salt levels in the coir. Coir is more expensive than peat moss in the US because of the shipping costs of transporting it from Asia. Using coir also requires cutting back on potassium in fertilizers and increasing nitrogen levels.

Peat moss has an acidic base, usually around 3.5 to 4 pH. Some plants like the high acidity levels of peat moss, but otherwise, limestone must be added to raise the pH level. Peat moss can often contain bacterial and fungal spores that can contaminate plants. It also attracts snails, which show no interest in coir.

Sustainability

Though industry officials tend to disagree, peat moss is considered by wetland ecologists to be harvested at unsustainable rates. Associate professor Alan Meerow of the University of Florida IFAS Extension believes that peat moss is unsustainable, as they take up to 25 years to renew after harvesting.

However, the Canadian Sphagnum Peat Moss Association, and Jeff Ball from Garden Rant make an interesting case for the renewability of peat. According to their studies, only one of every 6,000 acres of peat moss in Canada is harvested each year, and as peat bogs are considered living entities, they are believed to grow 70% more peat moss than what is harvested each year.

Coir, on the other hand, is always available, as it is a waste product of coconut harvests. The outer husks are removed with water, and processed into many products, one being soil amendments. Because coconut fiber is constantly available and grows on trees, it is widely considered to be a more sustainable resource than peat moss.

But not everyone believes that coir is as sustainable, nor as eco-friendly as it claims to be. Robert Pavlis at Garden Myths, believes that coir has been overhyped in this regard. Coir requires significant amounts of processing that uses lots of valuable water, which is already a limited resource in India, and leaves the water polluted after processing. His blog also cites a study that claims that working conditions in coir processing facilities cause worker health problems that would make such work illegal in Europe and the US.

Perhaps the most impactful long-term problem from coconut coir processing is the depletion of soil nutrients caused by growing coconuts in bulk and exporting the organic matter needed to replenish the soil. If you take into account the environmental damage that can be attributed to coconut farming and coir production, it hardly seems fair to label it as sustainable and eco-friendly in comparison to peat moss.

Cost

Though mentioned in the advantages and disadvantages sections that coconut coir is slightly more expensive than peat moss, the difference in cost is minimal, and is largely due to shipping costs for transportation of the products, as coconut coir costs more to transport to the USA from Sri Lanka and India than peat moss, which usually only travels from Canada to the US in comparison.

pH

Peat moss is acidic, with a pH level around 3.3 to 4.0, which is great for acid-loving plants, but could cause harm to plants that are less tolerant of low pH levels. Because of its low pH, peat moss is often used as a soil amendment to adjust and acidify soils that are too alkaline. For most planting needs, a neutral pH is preferred, so lime is often added to peat based soils before planting can occur. Most peat moss-based potting soils also include lime. Coconut fiber, in comparison, has a pH range of 5.2 to 6.8, which is much more acceptable to a much wider range of plants without the need of additives.

Water Absorption

Peat moss tends to shed water when first wetted, and coconut coir adjusts to water more easily than peat moss. Needing less time to become saturated, coir also needs less water. However, despite reports that coir has a greater water holding capacity, sphagnum peat moss holds 10 to 20 times its weight in water, while coir only holds an average of 8 to 9 times its weight. Peat and coco coir products also come in varying textures which can affect their ability to hold water.

Which medium is better for modern gardens?

With the results of varying studies and each medium having a different set of drawbacks as well as advantages, a clear winner is not easily discernible. Both mediums have their place in the gardening world, and both will continue to be used to improve garden soils around the world. With all of the information in hand, only you can decide which soilless potting alternative is right for you and your garden.

Common Questions and Answers About Peat Moss Versus Coconut Coir

Can coconut coir be used as mulch?

Coconut coir is a renewable resource that makes an excellent mulch for gardeners who need a mulch that offers plenty of drainage. At the same time, coir holds water—30 percent more than peat—keeping moisture accessible to plants. To use coir as mulch, soften the bricks in water for at least 15 minutes in a large container, as they will expand up to five to seven times in size after they’re hydrated. Then apply them as you would any mulch, in a layer two to three inches thick, taking care not to touch plants or trees with the mulch material. You can read more about the benefits of using coconut coir as mulch in our article on the topic.

Can I reuse my coco coir?

When the growing season is over, you can use coconut coir again the next season, as long as you take the time to recondition it properly. The fibers can last for years without decomposing, so it’s just a matter of removing leftover debris and washing the material to prepare it for reuse. First, use your hands to go through the coir, breaking up and removing any leftover roots that remain in the coir. There are enzymes on the market you can use to help with breaking down and removing old roots from the coir before using it again if you like. Then wash it thoroughly in distilled water to flush out salts left behind. Allow the coir to dry before using it again.

Can I use coconut coir for succulents?

The drainage that coconut coir offers makes it well suited to be a component in soil for growing succulents. Some gardeners recommend using a mixture of half pumice and half coconut coir, while other use three parts of a prepackaged soil blend designed for succulents, two parts pumice, and one part coconut coir. These mixtures are not only perfect for growing succulents; they work well for cacti as well.

Can plants grow in sphagnum moss?

Sphagnum moss’ capacity for water retention makes it a good choice for plants that thrive in moist soil. To use sphagnum moss in your container garden, first pick through the moss to remove any large pieces of grass, weeds, or other foreign debris it may contain. Soak the moss in a container of lukewarm water for a while, then remove it when you’re ready to use it and squeeze it out to remove most of the water so it isn’t saturated. Add a layer of sphagnum moss to the bottom of the container you’ll use, then add the plant, positioning the root ball in the middle of the container and filling in around the edges with more sphagnum moss. Pack the moss tightly enough to keep the plant in place when the container is tipped to one side. Water deeply, or you may choose instead to submerge the container in lukewarm water and let it soak until it stops producing air bubbles. Whenever the moss begins to dry out, it’s time to water the plant again. Try not to let the moss become completely bone dry in between waterings for best results. Use a fertilizer appropriate for what you are growing to feed your plants, as sphagnum moss doesn’t offer much in the way of nutrients.

Can you compost coconut coir?

Coir makes an excellent ingredient for composting because the carbon it contains helps to counterbalance the nitrogen in other ingredients, such as kitchen scraps. Use two parts coconut coir to one part green materials or one part coconut coir to one part brown materials. You can read our article on compost ingredients to learn about green and brown materials and what is suitable for composting.

Can you grow plants in just peat moss?

Plants that thrive in moist conditions can be grown in peat moss alone, or you can mix it with potting soil if your plants don’t need as much moisture. Use peat moss as you would any planting soil, watering when it becomes dry but not allowing it to dry out completely before the next watering. As an alternative to standard watering methods, you can soak container plants growing in peat moss in lukewarm water until they stop producing air bubbles for a deep watering. Because peat moss doesn’t offer much nutrition, be sure to use an appropriate fertilizer to keep your plants healthy.

Can you mix coco coir with soil?

You can mix coconut coir with soil, using up to 80 percent coir, to create a soil blend that drains well and lasts for years without decomposing. Coir is often sold in bricks that need to be soaked in water before use. Refer to the package for instructions on how much water to use with your brick of coir, and soak it in a large container. Coconut coir will expand up to five to seven times in size when it’s hydrated. Once it’s soaked, mix the coir with your hands to break up any clumps and separate the fibers. Then mix it with the soil you plan to use. The standard ratio is half coir and half soil. You can add compost at this time if you desire, or add one part perlite or vermiculite to further increase drainage. Then use your coir and soil blend as you would any planting medium.

Can you mix peat moss with potting soil?

Yes, peat moss makes a perfect component when mixing your own potting soil, especially for plants that need extra moisture. You can create your own blend by mixing one part peat moss with one part sand or vermiculite and one part compost. After combining these ingredients, add half an ounce of pelleted limestone and a quarter of an ounce of super phosphate or triple phosphate for each gallon of soil mixture. Increase the peat moss for moisture-loving plants, or add more perlite if you’re growing plants that require a drier soil.

Can you over water coco coir?

As with any planting material, it’s possible to give plants too much water when they’re growing in coconut coir. Generally, water plants growing in coir every day or two, and keep adding water until the moisture drips from the bottom of the container. If the coir is drying out before the day is up, consider moving plants to a larger container that will hold more moisture, keeping the water available longer so you don’t have to water them as often.

Can you start seeds in peat moss?

Because peat moss holds moisture so well, it’s optimal for starting seeds. You can start seeds in peat moss by itself or create a blend using one part peat moss along with two parts soil and two parts sand or vermiculite. Wet the soil before sowing seeds, and follow the directions for the seeds you have regarding how deep to plant them, as different types of seeds should be planted at varying depths. Lightly mist the seeds once they’re planted and cover them to keep humidity up with a lid, if your container came along with one, or use a clear plastic bag. Mist as needed to keep the soil evenly moist. Keep the seeds somewhere that stays between 65 and 75 degrees Fahrenheit where they will receive bright indirect light.

Do you water coconut coir every day?

Most plants growing in coconut coir need to be watered every day or two. You should water your plants until the moisture drips from the container’s drainage holes. If the coir is drying out too quickly, moving plants to a larger container will keep you from having to water them so often.

Does adding peat moss make soil acidic?

Peat moss is acidic, so depending on the pH level of your soil, it can increase its acidity. The pH level of peat moss is around 4.4, while neutral soil will have a pH of around 7. Some plants thrive in acidic soils, such as blueberries and azaleas. If your soil is already acidic and you aren’t growing acid-loving plants, peat moss is probably not the best planting medium for you. If you aren’t sure of your soil’s pH level, you can learn about testing to determine pH in our article “How to Test pH in Your Soil”.

Does coco coir go bad?

It takes years for coconut coir to decompose—some sources say decades. It can be reused for the next season, too, since it lasts so long. If you’d like to reuse your coconut coir, after the growing season has ended, go through the material to remove plant debris and any root pieces. Then soak it in lukewarm water for a while to clean it. Dry the coir before replacing it in your garden.

Does coco coir have nutrients?

Coconut coir does not provide plants with much nutrition, so it’s important to either use it mixed with a potting soil that contains the nutrients your plants need or to use it in conjunction with an appropriate fertilizer. Coconut coir is high in potassium, however, and it also contains manganese, copper, iron, and zinc.

Does coconut coir decompose?

Coconut coir does decompose, but it takes a long time. Your coir will be durable for years, and some sources even claim it lasts for decades. It can also be washed and reused season after season.

Does peat moss add nitrogen to soil?

Peat moss is low in nutrients and does not add nitrogen to soil.

Does peat moss go bad?

Peat moss that has not been used does not expire and can be used after a period of storage. However, peat moss that has been used may have reduced ability to retain water as well as reduced acidity.

Does peat moss have any nutrients?

Peat moss is low in nutrients, so it’s important to either combine it with nutrient-rich potting soil or use an appropriate fertilizer if you’re growing plants in peat moss.

How do you amend soil with peat moss?

To amend soil with peat moss, first put the peat moss in a large container and add water, then stir. Allow the water and peat moss to soak for a while, then add more water. Continue this process until the peat moss is completely saturated. When you squeeze a handful of the peat moss, a drop or two of water should come out, but you don’t want it so wet that a stream of water escapes when it’s squeezed. Then spread a layer of two or three inches over the area you wish to amend. Till or mix the top twelve inches of soil to work the peat moss through your garden’s topsoil.

How do you rehydrate coconut coir?

Coconut coir is usually sold in dehydrated bricks that you must rehydrate before the coir is ready to use in your garden. Use a large container to rehydrate your coconut coir, as it will expand five to seven times in size when rehydrated. Refer to the instructions on the packaging to tell you how much water needs to be added for your specific brick of coir. Allow it to soak, then mix the rehydrated coir with your hands to break up any clumps and separate the fibers. After you’ve mixed it, the coir should loosen and have a fluffy texture. Once it’s fluffy, it is ready to use.

How much lime do I add to peat moss?

When using dolomite lime to raise the pH of peat moss, the amount of lime to add varies depending on what you will grow. Plants that thrive in acidic soil, such as blueberries or azaleas, do best with just a sprinkling of lime. For growing vegetables and other plants that don’t thrive in acidic conditions, add between half an ounce and one and a half ounces of dolomite lime per gallon of peat moss.

How much water do I add to coir bricks?

The amount of water you’ll need to rehydrate a brick of coconut coir varies depending on your particular brick, but as a general rule, use eight parts water to one part coir.

How often do you feed in coco?

Because coconut coir does not offer any nutrition to your plants, use fertilizer each time you water them.

How often should I water plants in coconut coir?

Most plants growing in coconut coir need to be watered every day or two. You should water your plants until moisture drips out of the container’s drainage holes. Should you find that your coir dries out quicker and you’re having to water your plants more frequently than once per day, you can move them to larger containers so you don’t have to water them as often.

Is coco peat the same as coir?

Coconut coir and coco peat are the same material; the terms are interchangeable.

Is coconut coir organic?

Coconut coir can be an organic product when it is manufactured under organic conditions. However, not all coconut coir is organic. Check the packaging of coconut coir for the term “organic” when shopping if you’re looking for organic coir.

Is coconut coir flammable?

Coconut coir is not flammable.

Is coconut coir good for seed starting?

You can use coconut coir for seed starting, and many gardeners report success starting seeds in this growing medium. Rehydrate your coir blocks, referring to the packaging to determine how much water to add. Use a large container when rehydrating, as the coir will expand five to seven times. Mix it with your hands to separate the fibers and break up any large clumps until the coir is fluffy in texture. Then it’s ready to be used for seed starting just as you’d use any other planting medium.

Is coconut coir toxic to dogs or cats?

While coconut coir is not poisonous to dogs or cats, the dehydrated coir will expand when water is added. If the dehydrated coir is ingested, it can expand in the pet’s digestive system and cause intestinal blockage. If your pet has consumed dehydrated coir, contact your veterinarian.

Is coconut coir toxic to humans?

Coconut coir is not likely to be ingested as it is not particularly appetizing. However, should dehydrated coir be eaten, it will expand when water is added, and if this expansion occurs in the digestive tract, it can cause intestinal blockage. If a person eats dehydrated coir, they should contact their doctor or the Poison Control Hotline at 800-222-1222.

Is peat moss good for clay soil?

Peat moss is a good amendment for clay soil because it loosens the clay’s thick, heavy texture. Spread peat in a two-inch layer over the area you wish to amend, then mix it to a depth of four to six inches. For more on how to optimize clay soil for gardening, refer to our article “Amending Clay Soils”.

Is peat moss good for blueberry bushes?

The acidity peat moss adds to soil makes it especially beneficial for acid-loving blueberry plants.

Is peat moss toxic to dogs or cats?

Peat moss is not poisonous to dogs or cats. However, if pets ingest peat moss, they may suffer gastrointestinal irritation, including nausea, diarrhea, or vomiting. If your pet has digestive irritation after ingesting peat moss, contact your veterinarian. If pets roll in peat moss, they may also experience skin irritation. If your pet’s skin is irritated by peat moss, rinse their coat with fresh water. If peat moss comes into contact with the eyes of your dog or cat, it can also cause irritation. Should this occur, hold one eye open at a time, and rinse your pet’s eyes out with fresh water, saline, or pet eye wash. Continue until they have been rinsed out well. If eye irritation continues, consult your veterinarian.

Is peat moss toxic to humans?

Peat moss that contains the fungus Sporothrix schenckii can infect humans with sporotrichosis if the spores enter a person’s bloodstream through broken skin, such as a cut. When using peat moss, gardeners should reduce the risk of contracting sporotrichosis by wearing gloves, long sleeves, and long pants so skin is not exposed.

Is there a difference between peat moss and sphagnum peat moss?

Sphagnum peat moss and peat moss come from the same plant, but sphagnum moss is made of the dried plant, which may be milled to shorten the fibers. Peat moss that is not labeled sphagnum moss is made of the dead layers of moss that live moss grows on top of. As such, peat moss may contain parts of other plants, twigs, or anything else that was on the ground before the next layer of moss grew on top of it. Sphagnum moss has a neutral pH, while peat moss is more acidic, with a pH level around 4.4.

What are the advantages of coir?

Coconut coir has many advantages in gardening. It provides excellent drainage while still holding moisture to make it available for plants. It takes years to decompose and can be washed and reused season after season. It is also sterile and free of bacteria that can spread diseases to plants.

What are the benefits and advantages of peat moss?

Peat moss has many benefits and advantages in the garden. It adds acidity to soil, making it particularly beneficial to acid-loving plants like blueberries and azaleas. It takes years to decompose, making it an economical and practical soil medium or amendment. It also retains water well, holding several times its weight in moisture and keeping it available for plants. Although peat moss does not provide nutrients, it retains nutrients from fertilizers well so plants have easy access to them. It also does not contain the seeds from weeds and detrimental microorganisms that can be found in some composts.

What grows well in peat moss?

Peat moss has an outstanding capacity for holding moisture, making it optimal for seed starting. Its acidity also makes it a good choice for any plant that thrives in acidic soil, such as blueberries, azaleas, or camellias.

What is coconut coir made of?

Coconut coir is a natural material that is made of the fibers between a coconut’s hairy coat and its hard outer shell. 

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