Growmore, blood fish and bone, or chicken manure pellets — which should I use?

These three sit on the same shelf, cost broadly similar money, and are bought largely on habit. They are genuinely different — one is a mineral salt mix that dissolves on contact with moisture, the other two are organic materials that soil microbes have to break down first — and that difference decides which one is right for cold soil, for a quick correction, or for a long-term soil-building programme.

Safety

Step by step

1. Understand Growmore.A balanced mineral fertiliser, conventionally 7-7-7. All three nutrients are in mineral salt form and become available as soon as the granules dissolve, which means it works in cold spring soil when biological products have not started. Cheapest per unit of nutrient. Contributes nothing to soil organic matter, and it leaches readily from light soils.
2. Understand blood, fish and bone.Dried blood for nitrogen, fishmeal for nitrogen and phosphorus, bone meal for phosphorus and calcium. Typically around 3-9-3 or similar, so it leans towards phosphorus. Released by soil microbes over four to eight weeks, so it needs warmth. Adds a little organic matter. Attracts dogs and foxes strongly.
3. Understand chicken manure pellets.Composted and dried poultry manure, usually around 4-2-2 or 5-3-3, so nitrogen-leaning. Released over six to eight weeks by soil biology. Adds the most organic matter of the three by a distance, and improves soil structure alongside feeding. Bulky, so you apply and store much more of it for the same nutrients.
4. Choose by soil temperature if you are applying early.In February and March, soil biology is barely working and an organic product releases almost nothing. Growmore is genuinely better in cold soil. From late April onwards the organic products come into their own.
5. Choose by what the soil needs beyond nutrients.On a poor, low-organic soil, chicken manure pellets do two jobs at once and are the best value even though the nutrient cost is higher. On a soil already rich in organic matter, the extra bulk is not buying you anything.
6. Choose by phosphorus need.Blood, fish and bone is phosphorus-heavy, which suits establishing plants and root crops. But most long-cultivated British garden soils already have ample phosphorus, and repeatedly applying a high-phosphorus product builds it up further with no benefit. If you have never tested, this is a reason to.
7. Apply at the pack rate and rake in.All three go on as a base dressing before planting, scattered evenly and raked into the top 50mm. Water afterwards. Do not leave organic products on the surface where dogs and foxes can find them.
8. Do not treat any of them as a top-up feed for containers.They are base dressings for open ground. In a pot they are slow, unpredictable and easy to overdose. Use controlled-release granules and liquid feed for containers.

Tips

• For most gardeners the honest answer is that any of them, at the right rate at the right time, does the job — and the annual compost mulch matters more than which bag you chose.
• Chicken manure pellets are often the best-value organic option when compared per unit of nitrogen, and they are far easier to store and spread than fresh manure.
• Fish, blood and bone is the one to avoid if you have a dog. They will dig, and they will find it.
• Sulphate of potash added alongside any of these gives a potash-led base dressing for fruit, which none of the three provides much of.
• Buy the largest pack you will use within a season. All three keep well if sealed and dry, and none of them keeps well once damp.

Alternatives

• Seaweed meal: A slow soil amendment rather than a fertiliser — trace elements and alginates over months. Worth adding alongside one of the three rather than instead of it.
• Controlled-release granules: Coated mineral fertiliser that meters itself over three to six months in response to warmth and moisture. The right choice for containers, and overkill for open ground.
• Garden compost and manure: Lower in immediately available nutrients and far better for the soil. On an established, well-mulched bed this is often all that is needed.
• Sulphate of ammonia or dried blood: Single-nutrient nitrogen products for a specific correction — a nitrogen-hungry crop or a bed where woody material was incorporated. Not general feeds.

Questions people ask