John Innes

A recipe, not a brand

The first thing to know about John Innes is that it isn't a make of compost — it's a set of standard recipes. They were developed in the 1930s at the John Innes Horticultural Institution so that gardeners could buy a known, repeatable mix rather than gamble on whatever a supplier happened to bag up. Any company can make John Innes compost, as long as they follow the formula, which is why you'll see the same numbers on bags from completely different UK brands.

Every John Innes mix is loam-based. That means the backbone is sterilised loam (a balanced soil), blended with peat-free material or peat, sharp sand or grit for drainage, and a measured amount of fertiliser. The loam is what sets it apart from the lightweight, peat-free multipurpose bags most people reach for first.

The numbered grades

The numbers don't mean better or worse — they describe how much plant food the mix contains, which suits different stages of a plant's life:

• John Innes Seed Compost — low in nutrients and finely textured, made for sowing seeds and rooting cuttings, where too much feed can scorch tender roots.
• No.1 — a small amount of fertiliser, for pricking out and potting up young seedlings.
• No.2 — roughly double the feed of No.1, for general potting on of established plants into medium pots.
• No.3 — the richest, for hungry, vigorous plants and long-term residents like tomatoes, shrubs and fruit in big containers.

As a rough rule, the bigger the plant and the longer it'll sit in its pot, the higher the number you want. Move plants up the scale as they grow rather than starting a seedling in No.3.

When loam-based beats multipurpose

A loam-based mix has real advantages over a bag of multipurpose compost. The soil content gives it weight, so tall plants and top-heavy pots are less likely to blow over. It holds on to nutrients and water more steadily, and it doesn't shrink, dry out or break down as quickly — which matters for anything staying in the same pot for a season or more.

That makes John Innes the sensible choice for permanent and long-term plantings: patio trees, shrubs, fruit bushes, and big tomato or pepper pots. Many growers mix it half-and-half with peat-free multipurpose to get the best of both — lighter to handle, but with the staying power of loam.

Where multipurpose still wins is cost, weight to carry, and quick crops like salad leaves or bedding that won't be in their pots for long. For those, a standard bag is fine. Keep John Innes for the plants that need to stay put and stay fed.