How to Make Your Own Coco Coir Potting Mix

One of the biggest advantages of coco coir is that you can create custom potting mixes tailored to exactly what you are growing. Pre-mixed bagged composts are convenient, but making your own gives you better results at a fraction of the cost.

Why Make Your Own Potting Mix?

• Cost savings — a 5kg coco coir brick expands to 75 litres for a fraction of the price of premium bagged compost
• Quality control — you know exactly what goes into your mix
• Customisation — different plants need different ratios of drainage, moisture, and nutrients
• Consistency — commercial peat-free composts vary between batches; your own mix is always the same
• Peat-free — fully sustainable with no environmental guilt

Essential Ingredients

Coco Coir (Base)

The foundation of every mix. Provides moisture retention, structure, and aeration. Always use buffered coco coir to prevent calcium and magnesium issues.

Perlite (Drainage)

Volcanic glass expanded into lightweight white granules. Adding perlite prevents waterlogging and improves root aeration. Available from most garden centres.

Vermiculite (Moisture + Minerals)

Holds water and provides trace minerals. Use instead of (or alongside) perlite when you want higher moisture retention.

Worm Compost or Garden Compost (Nutrients)

Adds slow-release organic nutrients. Worm compost (vermicast) is the gold standard — see our guide to setting up a worm farm with coco coir.

Slow-Release Fertiliser (Optional)

Granular feeds like Osmocote or Vitax Q4 provide 3–6 months of nutrition. Useful for outdoor containers where regular liquid feeding is inconvenient.

DIY Potting Mix Recipes

All-Purpose Mix

Suitable for most houseplants, annuals, and container vegetables.

• 70% coco coir
• 20% perlite
• 10% worm compost or garden compost
• Optional: 3g slow-release fertiliser per litre of mix

Seed Starting Mix

Fine, clean and safe, and moisture-retentive for delicate seedlings.

• 80% coco coir (finely sieved)
• 20% fine perlite or vermiculite
• No fertiliser — seedlings use energy stored in the seed for the first few weeks

Succulent and Cactus Mix

Fast-draining for plants that hate wet feet.

• 50% coco coir
• 30% perlite
• 20% coarse sand or grit

Raised Bed Mix

Nutrient-rich and well-structured for raised bed growing.

• 40% coco coir
• 30% garden compost
• 20% topsoil
• 10% perlite
• Add slow-release fertiliser at the recommended rate

Tomato and Vegetable Mix

Moisture-retentive with good nutrient capacity for heavy feeders.

• 60% coco coir
• 20% perlite
• 20% worm compost
• Add tomato fertiliser or slow-release granules

How to Mix

• Step 1: Hydrate the coco coir brick in a large container or wheelbarrow.
• Step 2: Add perlite and compost. Mix thoroughly with your hands or a trowel.
• Step 3: If adding slow-release fertiliser, sprinkle it in and mix evenly.
• Step 4: Moisten the mix until it feels like a wrung-out sponge. It is ready to use.

Storage Tips

Mixed potting compost stores well in sealed bags or bins for several months. Keep it in a cool, dry place. Coco Coir does not harbour mould or pathogens, so your mix will stay fresh much longer than soil-based composts.

Cost Breakdown

A 5kg coco coir brick (75 litres) plus a bag of perlite and some compost gives you 80–100 litres of premium potting mix for roughly half the price of branded bagged compost. The 15kg 3-pack (225 litres) brings the per-litre cost down even further.

Making your own coco coir potting mix is simple, cost-effective, and gives you complete control over what your plants grow in. Once you start, you will never go back to pre-mixed bags.