TL;DR Summary

John Innes composts are classic soil-based growing media developed in the 1930s by horticultural scientists at the John Innes Horticultural Institution. They remain excellent for structured, long-term container growth — but differ completely from today’s soilless Multipurpose Composts (MPCs). The formulas are public domain and can be made at home using garden soil, sand and fertiliser; many modern “John Innes” bags are only loosely based on the original science.

What Is John Innes Compost?

“John Innes compost” refers to a set of standardised, soil-based potting mixes created in the 1930s at the John Innes Horticultural Institution (now the John Innes Centre, Norwich).

Researchers William Lawrence and John Newell designed the recipes to provide reliable seedling survival and balanced nutrition for laboratory and greenhouse trials.

• Sterilised loam (garden soil)
• Peat (for moisture retention)
• Sharp sand (for drainage)
• John Innes Base fertiliser — hoof & horn, superphosphate, sulphate of potash
• Ground limestone to buffer acidity

The original formulas were published openly for public benefit — there is no commercial ownership, though the John Innes Manufacturers’ Association later formed to encourage recipe consistency.

The Classic Recipes: Seed, No 1, No 2 and No 3

Mix	Typical Use	Nutrient Level	Comment
John Innes Seed	Germinating seeds & cuttings	Very low	Fine-textured, minimal fertiliser
John Innes No 1	Potting-on young plants	Low	Gentle feeding after pricking out
John Innes No 2	Established plants & vegetables	Medium	Balanced all-purpose mix
John Innes No 3	Mature plants, shrubs, trees	High	Long-term feeding for large containers

Each mix uses the same base ratio (7 parts loam : 3 parts peat : 2 parts sharp sand) and varies only in fertiliser loading.

Why the Recipe Works Scientifically

• Loam adds cation-exchange capacity (CEC) and nutrient buffering
• Sand and grit ensure aeration and drainage
• Lime stabilises pH around 6.5–7
• The fertiliser base provides slow-release nutrition
• Predictable, repeatable performance for pot culture

Drawbacks commercially: heavy to ship, requires sterilised loam, peat dependence (now phased out), costlier than lightweight MPCs, and not suited to high-speed retail mixing lines.

How to Use John Innes Compost

• Start with Seed mix for germination or cuttings.
• Pot into No 1 when seedlings have roots or 2 true leaves.
• Move to No 2 as plants grow and feed demands rise.
• Finish in No 3 for long-term pots, shrubs, or trees.
• Top up feeding after 6–8 weeks if growth slows.

Remember: these are structured soil mixes, not “fluffy” Multipurpose Compost blends — they retain water and nutrients differently.

Can I Make My Own John Innes Compost?

Absolutely — and unless convenience is essential, you should. Because the recipes are public domain, any gardener can recreate them.

DIY John Innes Base Recipe (by volume)

• 7 parts good garden soil (loam) — sieved and weed-free
• 3 parts composted organic matter (old compost, coir, or bark fines)
• 2 parts sharp sand or grit
• Per 10 L of mix: 1 heaped tablespoon of John Innes Base fertiliser (or NPK 5-7-10)
• Add 1 teaspoon of ground limestone (omit for ericaceous plants)

Tip: Lightly sterilise your garden soil (e.g. heat at ~80°C for 30 minutes) for a clean, peat-free, John Innes-style mix.

Is Multipurpose Compost the Same as John Innes?

Feature	John Innes	Multipurpose Compost (MPC)
Base Material	Soil (loam) + sand + peat/peat-free substitute	Loamless organic materials (bark, coir, green waste)
Texture	Dense, structured, heavy	Light, spongy
Nutrient Buffering	High	Low
Weight / Handling	Heavy	Light
Durability	Long-term stable	Breaks down quickly
Best Use	Container shrubs, trees, long-term pots	Short-term bedding, sowing, patio planters

Many retail bags labelled “Multi-purpose with added John Innes” contain only a token amount of loam or grit — useful, but not a true JI mix.

What About Peat-Free John Innes?

• Wood fibre
• Composted bark
• Coir
• Occasionally biochar

These substitutes differ chemically, so lime and fertiliser ratios need adjusting. Performance varies — check drainage, pH and structure before bulk use.

Why the Term “John Innes” Is Often Misunderstood

• The name describes a recipe, not a brand.
• Many commercial “John Innes” composts contain minimal loam.
• The John Innes Manufacturers’ Association promotes best practice but cannot enforce strict composition.
• Always check the ingredient list for loam and grit content.

Historical Timeline Snapshot

Date	Milestone
1904	John Innes dies, leaving his estate for horticultural science
1910–1930s	John Innes Horticultural Institution established
1938	Lawrence & Newell publish the JI compost formulae
1950s–1970s	Widespread commercial adoption in UK nurseries
1980s–2000s	Shift toward lighter, peat-based MPCs
2020s	Transition to peat-free John Innes versions
Today	JI recipes remain a gold-standard reference for soil-based media

Summary

John Innes composts represent a technically excellent, soil-based growing system born from early horticultural science. While many modern “JI” bags deviate from the original, the underlying idea — structured, buffered, biologically stable media — remains unmatched.

Unless you need convenience, make your own John Innes — sieve your own soil, mix in sand and a little fertiliser, and you’ll have a superior, peat-free, low-cost medium.