What Is Coco Soil? Coconut Husk, and It Is Not Really Soil

Coir is the fibre left over from coconut processing, used as a peat substitute. It holds water well, has almost no nutrients, and needs buffering.

By Zakaria October 12, 2026 3 min read Save to Pinterest

A coconut split open with a hammer, showing the fibrous husk inside — Photo: Hans, Pixabay Content License, via Pixabay

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Coconut husk fibre — and it is not soil. Coir contains no mineral soil and almost no nutrients. It is a physical medium that holds water and air; you supply the feeding. Most of it also needs buffering before use.

The short answer

Coco soil, properly called coir, is fibrous material from coconut husks sold compressed into bricks or loose, used as a growing medium and peat substitute. It contains no mineral soil and almost no nutrients, so it holds water and air while the grower supplies all feeding. It rewets easily where dried peat repels water, and is a waste product rather than a mined resource. Raw coir holds potassium and sodium that displace calcium and magnesium from feed, so it needs buffering unless sold pre-buffered.

Coconut husk fibre, not soil — no minerals, no nutrients
Holds water and air; you provide all the feeding
Rewets easily where dried-out peat repels water
Needs buffering unless the bag says pre-buffered
Best as a third to a half of a mix, not neat in a garden pot
Coarser chip grades for plants that dislike wet roots

Coir against peat

This table answers the question on its own

	Coir	Peat
Source	Coconut waste product	Mined from peat bogs
Rewetting when dry	Easy	Repels water stubbornly
Drainage	Slightly freer	Holds tighter
Nutrients	Essentially none	Essentially none
pH	Near neutral, 5.5–6.8	Acidic, 3.5–4.5
Preparation	Rinse and buffer	None
Environmental cost	Shipping	Habitat that takes millennia to form

Why buffering matters

Raw coir holds a lot of potassium and sodium on its exchange sites. When you feed the plant, the calcium and magnesium in the feed displace them — which both wastes your fertiliser and delivers a salt dose to the plant.

Buffering just means pre-loading those sites

Soak the coir in a calcium and magnesium solution before use, so the exchange sites are already occupied. Good coir is sold pre-buffered and says so on the bag. Cheap coir usually is not — and cheap coir is also the kind most likely to arrive salty from poor washing.

Rehydrating a block

Big container — a 5 kg brick makes far more than it looks like it will.
Several times its volume in warm water.
Twenty to thirty minutes, breaking it up by hand as it swells.
Squeeze a handful: damp and springy, with only a few drops coming out.
If it is sodden, let it drain before use.

Using it

As a mix component — roughly a third to a half, with compost for feeding and perlite for drainage. This is the right answer for ordinary garden use.
Neat, hydroponically — works, and routine among hydroponic growers, but you must supply all the nutrition.

Pure coir with no feeding regime fails predictably

You get healthy-looking young plants that stall and yellow within weeks, because there was never anything in the medium to feed them.

Water holding

Fine coir pith is very absorbent and can stay wet in a pot with poor drainage. Coarser chip grades hold more air.

Same fix as any over-wet mix: add perlite, and choose the coarse grade for orchids, succulents and anything prone to root rot.

Common questions

What is coco soil?

Coco soil, usually called coir, is the fibrous material from the husk of a coconut, left over after the fibre industry has taken what it wants. It is sold compressed into bricks or loose, and used as a growing medium or as a peat substitute in potting mixes. Calling it soil is a misnomer — it contains no mineral soil and almost no nutrients, so it is a physical medium that holds water and air while you supply the feeding.

Is coco coir better than peat?

It is comparable on performance and much better on environmental grounds, which is the main reason to use it. Coir rewets easily where dried-out peat repels water stubbornly, it drains a little more freely, and it is a waste product rather than a mined resource from habitats that take millennia to form. Against that, it is shipped a long way, needs rinsing and buffering, and some cheaper coir arrives salty.

Why does coir need buffering?

Because raw coir holds a lot of potassium and sodium on its exchange sites, and when you feed a plant the calcium and magnesium in the feed displace them, which both wastes your fertiliser and can give the plant a salt dose. Buffering means soaking the coir in a calcium and magnesium solution beforehand so those sites are already occupied. Good quality coir is sold pre-buffered and says so; cheap coir usually is not.

How do you rehydrate a coir block?

Put the brick in a large container, add several times its volume in warm water, and leave it for twenty to thirty minutes while it expands — a standard 5 kg block makes a surprisingly large volume, so use a bigger tub than seems necessary. Break it up with your hands as it swells, then squeeze a handful; it should feel damp and springy with only a few drops coming out. If it is sodden, let it drain before use.

Can you grow in pure coir?

Yes, and hydroponic growers routinely do, but it requires you to supply all the nutrition since coir provides essentially none. For ordinary garden use it is better as a component — roughly a third to a half of a mix alongside compost for feeding and perlite for drainage. Pure coir in a garden pot with no feeding regime will give you healthy-looking young plants that stall and yellow within weeks.

Does coir hold too much water?

It holds a great deal, which is usually its strength and occasionally a problem. Fine coir pith is very absorbent and can stay wet in a pot with poor drainage, while coarser chip grades hold more air and suit plants that dislike wet roots. The practical fix is the same as for any mix that holds too much — add perlite, and choose a coarser grade for orchids, succulents and anything prone to root rot.

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A handful of dark potting mix with white perlite granules visible through it

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