How to Use Coconut Coir in the Garden (Questions and Answers)

Coconut coir is a versatile growing medium that can be used as an ingredient in potting mix, in hydroponics, and even for growing mushrooms. You may have seen people using it or just noticed it in nurseries or online while shopping for garden supplies. Is it worth using in your garden?

Read more to learn about what coconut coir actually is, how to use it, and answers to other common questions about this alternative to peat moss.

What Is Coconut Coir?

Coconut coir, also called coco coir, coco peat or just coconut fiber, is the fiber removed from the woody outer husk of coconuts.

Coconut fiber is a natural by-product of coconut cultivation and processing, and until recently was mostly a waste product. However, it’s become a useful fiber for textiles and ropes, and in recent years has seen a surge in popularity among gardeners.

Because coconut coir is just fibrous plant matter that absorbs a lot of water, it’s often used as an alternative to peat moss. Not only that, but coco coir has become popular among hydroponic growers looking for a soilless growing medium.


How to Prepare Coco Coir for Use

For most of us, we are going to get coco coir in large compressed blocks which need to be soaked in water before we can use them. They don’t look like much, but they will expand several times their size once fully hydrated. Most packages will say roughly how much volume they take, but as a rule of thumb, 2.2 lbs (1 kg) of compressed coco coir will expand to fill up nearly 4 gallons (15 L) of volume. To fully hydrate coco coir, use about 0.5 gallons of water per 1 lb compressed coco coir. However, you can simply add more water and wring out the excess later.

The simple way to hydrate coco coir:

  1. Take the whole compressed block or chunks of it and place it into a large container (at least 2-3 times the size of the amount of coco coir you’re hydrating).
  2. Pour hot water over your coco coir and let it soak for at least 15 minutes.
  3. Break up, mix, and fluff up your coco coir until it’s evenly moist. Add more water or squeeze out excess water as necessary.
  4. Let your coco coir cool down before planting anything in it.

Pro-Tip: If when you pick up a handful of coco coir it’s still dripping with water, it has too much water. Squeeze out the excess and you can use it in containers, raised beds, or seed starting mixes.

Pro-Tip: For mushroom cultivation, the optimal hydration level is at field capacity which is when you get a few drops to barely a stream of water after squeezing the coir hard in your hand.

Does Coco Coir Need to Be Washed?

If you buy unprocessed bulk coco coir, it should be washed to remove excess sea salt. However, if you are using garden-grade or hydroponic-grade coco coir, it has already been washed and is immediately ready to use.

Because most coconut fiber is processed along the sea, it naturally has a higher salt content, which can be disastrous if using it in the garden. Fortunately, most coconut coir blocks for gardening have already been washed. Be sure to buy coco coir labelled for garden or hydroponic use, otherwise you will have to wash it by soaking it in water and draining several times.


Do You Need to Sterilize Coco Coir?

Whether you sterilize coco coir or not depends on what you’re using it for.

In most garden applications, you do not need to sterilize coco coir, although some gardeners will sterilize it to make seed-starting mix. For growing mushrooms, coco coir should always be sterilized before use.

Coconut coir is naturally non-sterile and has fungal spores which are generally harmless to plants. If you are making seed-starting mix, as an added precaution you can sterilize it beforehand as coco coir rarely may have pest eggs in it as well.

If you are using coco coir as a medium for mushroom cultivation, you should sterilize it so the mycelium of your mushrooms have no competition for nutrients.

How Do You Sterilize Coco Coir?

To sterilize (or more accurately, pasteurize) coco coir, bake it in a 180-200°F (82-93°C) oven for at least 30 minutes.


Coconut Coir Mix Recipes

Basic Coconut Coir Potting Mix Recipe

  • 40% coconut coir
  • 40% compost
  • 20% perlite

Basic Sterile Coconut Coir Seed-Starting Mix Recipe

  • 60% coconut coir
  • 40% perlite or vermiculite

Note: Since neither coconut coir and perlite/vermiculite have nutrients, you will need to lightly fertilize your seedlings after they grow their first set of true leaves (= the leaves after their first two seed leaves).


Related Questions About Coconut Coir

Does Coco Coir Have Nutrients?

Coco coir does not have any plant-available nutrients.

Since coco coir doesn’t have nutrients, you will need to keep this in mind if using it as a growing medium or alternative to soil. Being made of natural fibers, coco coir will gradually be broken down by soil life and help enrich the soil, but this process is too slow if you are just growing plants in coco coir.

Is Coir Peat the Same as Peat Moss?

Coco coir or coco peat is not the same as peat moss. Coco coir is extracted coconut husk fiber while peat moss is partially decomposed and dried spaghnum moss. Coco coir will have close to neutral pH while peat moss has a more acidic pH. Both, however, are readily interchangeable in potting mix recipes.

Is Coco Coir More Sustainable than Peat Moss?

There are some questions about whether coco coir is a more sustainable alternative to peat moss in the garden. This is a hotly debated topic but the answer is not cut and dried.

Coco coir and peat moss both have sustainability costs and benefits. Coco coir is a by-product of coconut cultivation and highly renewable, however it’s produced mostly in countries with fewer labor standards. Peat moss regenerates much more slowly, however, most peat is produced in Canada with sustainable peat mining operations.

Is Coconut Coir Good for a Garden?

Coconut coir can be added to a garden much like peat moss, either as part of a potting mix or mixed in with soil. Coco coir can also be used as a mulch, although it’s not as economical as using wood chip or straw mulch.

The benefits of coconut coir include increasing water retention and adding bulky organic matter to soil. In addition, coconut coir breaks down naturally over time, which will improve soil structure.

Can You Use Coco Coir Instead of Soil?

Using only coco coir as a soil substitute can be done but it doesn’t have as much drainage as a coir-based potting mix with added perlite or vermiculite. You will also need to fertilize regularly.

Can You Grow Vegetables in Coco Coir?

Coco coir can be used for growing vegetables. When used as part of a potting mix, you can grow nearly any kind of vegetable. Gardeners have grown peppers, tomatoes, leafy greens, and even melons in coir-based potting mix.

Note that vegetables grown in homemade coir-based potting mix will need to be fertilized regularly unless compost or other rich organic matter is added.

Is Coconut Coir Biodegradable?

Yes, coconut coir is 100% biodegradable.

It will break down over time if left outside or mixed with soil. In fact, some gardeners specifically add coconut coir to their garden beds to help improve the soil.

Does Coco Coir Go Bad?

Dry coco coir doesn’t spoil or go bad, as it’s a tough plant fiber. That said, coco coir is biodegradable and will break down over time if left in soil or outside. Furthermore, mold and algae can grow on moist coco coir. But dry coco coir will maintain its quality almost indefinitely.