Coco Coir Compost vs. John Innes Composts
Background – Why Potting Media Recipes Have Changed
John Innes compost is not a brand but a set of soil-based compost recipes developed in the 1930s at the John Innes Horticultural Institution. These mixes, originally used in the Dig for Victory campaign, rely on sterilised loam, peat, and coarse sand for structure, along with base fertilisers such as hoof and horn meal, superphosphate, sulphate of potash, and ground chalk.
Traditional John Innes recipes became popular due to their stable structure, good buffering capacity, and presence of essential trace elements. The soil component helps regulate water and nutrient availability, making it easier to manage than entirely soil-free composts.
However, several factors have contributed to significant changes in potting media:
- Environmental concerns about peat: Extracting peat releases carbon and destroys valuable peatland ecosystems. UK regulations now prohibit the sale of peat-based compost to amateur gardeners, and many horticultural bodies support a transition to peat-free alternatives.
- Shortage of loam and ingredient variation: Loam, a key component in the original formula, is now in short supply. Many modern versions of John Innes compost replace loam and peat with substitutes such as composted bark, coir, or other organic materials.
- Inconsistent quality: Reports from gardening groups and trials show a decline in consistency and performance of modern John Innes composts. Some now contain very little loam and exhibit poor germination rates, leading gardeners to question their reliability.
These changes have led to increased interest in alternative potting media—such as coco coir compost.
What is Coco Coir and How It’s Produced
Coco coir is an organic, renewable material derived from coconut husks. During processing, the husks are soaked, beaten, and sieved. The longer fibres are removed for other industries, leaving behind a spongy, fine-textured pith. This pith is washed to reduce salt levels, dried, and compressed into blocks or bricks.
When rehydrated, coir has a neutral pH of approximately 6.0–6.8 and is primarily composed of lignin and cellulose. As a by-product of the coconut industry, coir is considered environmentally sustainable and has a significantly lower ecological impact than peat.
Properties and Benefits of Coco Coir Compost
Water Retention and Aeration
Coco coir retains water well while remaining aerated, making it ideal for seedling root development. Its light, porous texture allows air to circulate while keeping the roots moist, reducing the risk of fungal diseases such as damping-off.
Root Development and Microbial Activity
Coir supports healthy root growth and encourages beneficial microbial activity. As it is sterile and free from weed seeds or pathogens, coir reduces the risk of seedling disease during the vulnerable early stages of growth.
Buffering Capacity and Nutrient Exchange
While coco coir does have some cation exchange capacity, it is lower than that of loam. It can hold and release nutrients but is less effective at long-term retention. This makes it important to supplement coir-based composts with regular feeding, especially for long-term crops.
Environmental Sustainability
Coir is a sustainable choice because it is a by-product of the coconut industry. Its production does not damage natural carbon stores and provides an effective way to use agricultural waste.
Other Benefits and Limitations
Coir has a neutral pH, is consistent across batches, does not shrink or crack when dry, and is pleasant to handle. On the downside, it holds fewer nutrients than peat or loam and breaks down over time. If not properly washed, it may contain salts—so sourcing from a reputable supplier is key.
Comparing Coco Coir Compost with John Innes Composts
| Feature | John Innes Composts | Coco Coir Compost |
| Origin and Ingredients | Developed using loam, peat (or substitute), sand, and fertilisers | Made from coconut husk pith; inert and low in nutrients |
| Consistency and Quality | Variable across brands; declining loam content in many versions | Physically consistent; sterile and seed/pathogen-free |
| Water Retention & Drainage | Holds moisture well but may compact with low loam content | Excellent moisture retention and aeration; reduces damping-off |
| Nutrient Content | Naturally rich due to loam and added fertilisers | Very low; must be supplemented with fertilisers |
| pH and Buffering | Peat-based mixes are acidic; buffering via loam and chalk | Neutral pH; lower nutrient buffering capacity |
| Environmental Impact | Peat extraction harms habitats and releases carbon | Renewable, low-impact by-product of coconut production |
| Cost and Availability | Widely available but quality varies; often inconsistent | More expensive, but expands well; cost-effective in bulk |
Practical Advice for Gardeners
- Use Coir for Seed Sowing and Cuttings
Its light structure and moisture balance make it excellent for germination. Because seeds contain their own food reserves, coir’s low nutrient content is not an issue early on. - Supplement Nutrients
Once plants grow beyond the seedling stage, add a balanced fertiliser or blend the coir with loam-based compost. Apply liquid feeds weekly from around six weeks onwards for best results. - Monitor pH and Salt Levels
Choose coir products that have been washed and buffered. Occasional pH testing can help guide fertiliser choices, especially for plants with specific needs. - Re‑use and Recycle Coir
Coir can be reused if properly fertilised and sterilised between uses. Old coir can also be used as a soil improver in garden beds, where it enhances aeration and moisture retention. - Choose Quality John Innes Products
If you prefer soil-based compost, select John Innes mixes that are clearly labelled as peat-free and look for signs of quality assurance to ensure consistency.
John Innes composts still have a role to play in gardening, especially for long-term container growing due to their nutrient content and buffering capacity. However, modern issues—such as inconsistent quality and environmental concerns—have prompted many gardeners to look for alternatives.
Coco coir compost stands out as a reliable, peat-free option. It offers excellent aeration, water retention, and root support while being sustainable and consistent. Though it lacks nutrients and may cost more, these drawbacks can be addressed with proper feeding and sourcing.
For those focused on sustainability and dependable germination, coir compost—used on its own for seedlings or blended with loam for more mature plants—provides a practical and eco-friendly solution.
