Get Started With Coco Coir in Your Garden

Coconut coir, also known as coco coir or coco peat, is fast becoming one of the most popular growing mediums in the UK and for a good reason, but if you’re new to using coir in your garden, check out my guide to the seven things you need to know before you start.

What is Coco Coir?

Coco coir is a by-product of the coconut industry and is made from the husk, which traditionally was discarded as a waste product of little value.

The coir is a fibrous material which can be used by gardeners as a growing medium as it’s similar to peat but is far more environmentally friendly.

How is Coconut Coir Made?

The process of turning coconut husks into coir is long and involves soaking the material in either fresh or saltwater for months to loosen it from the coconut shell.

Good quality manufacturers then wash the coir to remove any salt, treat it to kill off any bacteria so it’s as inert as possible with a neutral pH.

The coir is then dried, packed and shipped.

Gardeners buy coir in dry, compressed bricks, which are lightweight but they will need to hydrate it with water to reconstitute it before using it in the garden.

I’ve used coco coir several times in my garden and in pots and it can also be used in hydroponic setups.

7 Things Every Gardener Should Know Before They Start With Coco Coir

Here’s my guide to getting started with coco coir in your garden:

1) Coco Coir Has No Nutritional Value

Many gardeners that I’ve spoken to seem surprised when they first realise that coco coir has no nutritional value whatsoever and that it won’t feed their plants.

Coco coir can still be an excellent product to grow plants in, and if used correctly, your plants will develop strong roots that will maximise the number of nutrients the plant can uptake from other sources.

2) You’ll Need to Add Nutrients.

As coco coir has no nutrients in it, you’ll need to your own, and you have a few options:

• Add compost – a simple and easy step that will provide nutrients for well over a month.
• Add wormcasts, manure or similar.
• Add slow-release fertiliser pellets.
• Add quick-release fertiliser dissolved in water.

I try to think of coco coir has a base material where I can then customise the nutrients specifically for the plants I intend to grow. The coir retains nutrients very well, so once added, they won’t just flush out with every watering.

3) It Can be Very Forgiving to Over or Underwatering

Coir is well known for its water-retaining properties; it can hold moisture well without the material becoming clogged, it also remains very well aerated, even after heavy watering. That means the roots of your plants have access to moisture but are unlikely to rot due to overwatering.

You might be surprised to know that coir holds between 8 and 10 times its volume in water. I’ve seen this myself as when I added water to the dry bricks they expanded to several times their size and weight.

I feel coco coir is very forgiving to overwatering, underwatering and even irregular watering, making it perfect for lazy or busy gardeners,

I try to think of coco coir as an excellent moisture regulator, while the surface may appear dry, it takes a long time for the coir in pots and baskets to fully dry out.

4) Not All Coco Coir is Made The Same

Coconut waste products can be used to make many dozens of different items, from hanging basket liners to doormats, rope and even animal bedding material.

However, as the coconuts are grown close to the sea and usually soaked in seawater as part of the manufacturing process, coco coir may have a high salt content. Salt can be detrimental to plant growth and can block plants from uptaking calcium, magnesium and iron.

Good quality manufacturers should thoroughly flush the coco coir. If gardeners wish to use it as a growing medium, it should also be treated with a calcium, magnesium and iron solution, so the salts don’t create nutrient deficiencies in the plants, this process is called buffering.

For plants sensitive to iron, magnesium and calcium deficiencies, I recommend Canna Coir, it’s more expensive than some other brands but is a professional grade product that’s also popular with commercial cannabis growers.

My first experience of using coco coir was with a cheap brand and led to iron and calcium deficiencies in our long trailing petunia plants and also a high pH number which I discovered after testing the soil.

After correcting the coir with some additives, the plants went from strength to strength and have significantly outgrown the petunias I grew in regular compost.

If you want to flush and buffer the coir yourself, go with any brand but if you’re just starting out, try a trusted name like Canna:

Canna coco coir is:

• Treated for bacteria and viruses.
• Fully buffered, eliminating the side effects of growing in coco coir.
• Pure and organic, better for the environment than peat.
• Professional grade.
• Perfect as a base for mixes including compost and organic matter.

5) It Will Breakdown and Degrade – Eventually

Coco coir is 100% organic but is long-lasting and takes years to degrade and breakdown in the soil.

If you’re using coco coir on its own, you can reuse it the following year.

Mixing coir with composts and organic matter for pots, hanging baskets and containers? Just dig the waste material into your flower beds at the end of the season, it will help aerate the soil and won’t cause any issues whatsoever.

6) It Works Great With Perlite, Grit and Vermiculite

Perlite and vermiculite are minerals that absorb and slowly release moisture, they also create air pockets when added to a potting mix.

Used with coir, they improve moisture control and aeration even further.

The end result? With the correct nutrients, you can expect the roots to grow in near-perfect ground conditions; moist but never saturated media, plenty of aeration with no compaction or issues with lack of oxygen. Also, coir absorbs and holds onto the added nutrients.

Horticultural grit is often found in potting mixes for seeds, seedlings and cuttings as it helps to aerate the mix, making it easier for the young roots grow. 

You can add grit to coir, along with perlite, vermiculite and organic material, together they make a great potting mix for containers and baskets.

Perlite is:

• Perfect for adding aeration to soils and potting mixes.
• Retains moisture so keeps the soil moist but not waterlogged.
• Harmless and safe to use.
• Can be used with coco coir, vermiculite, grit and fertilisers.
• Often in potting mixes for seeds, seedlings and cuttings.

7) Coir is an Eco-Friendly Alternative to Peat

Gardeners have been using peat as a growing medium for years, but the process of digging up peat bogs produces considerable amounts of CO₂.

Read more: The Guardian on peat and the environment.

Coco coir is an environmentally friendly alternative that growers can use in gardens and hydroponics. You do, however, need to be aware of potential issues with high salt/potassium content blocking the uptake of iron/calcium and magnesium in some plants.

Suggested Potting Mix

I feel the following mix would be perfect for hanging baskets or window boxes and is a good starting point for anyone looking to use coco coir for the first time:

• 50% coco coir.
• 30% nutrient-rich material, ie compost, manure, worm castings or a mixture of these.
• 20% perlite, vermiculite and horticultural grit.
• Slow-release fertiliser pellets.
• Quick-release water-soluble fertiliser to top up as required.
• Sequestered iron with magnesium which cures leaf yellowing (interveinal chlorosis) in line-hating plants.

See more of our suggested potting mixes here.

My Experience With Coco Coir

In 2020 I experimented by using coco coir in all my potting mixes and by adding it to troughs, hanging baskets and containers.

I liked that it was lightweight and came in bricks which expanded when soaked in water – I wanted to reduce my reliance on peat and compost, and coir seemed like a good option.

Overall, I’ve had a positive experience with coco coir but I did have to pay more attention to the nutrients I fed the plants as coir is essentially inert. 

I found that the mix held moisture well, didn’t dry out too quickly, and the plants thrived.

Based on my experience, I believe coco coir best suits younger plants when the roots require some space to grow into.

Inspiration and Ideas

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