Organic Fertilisers

Organic fertiliser is plant food whose nutrients sit in natural materials — milled meals, seaweed, composted matter, mined minerals — and are released by soil organisms over weeks rather than dissolving the moment you water. In the garden centre sense it means “not a manufactured soluble salt”, which is why mined minerals such as rock phosphate and sulphate of potash still count. It is not the same as a whole-product organic certification logo on every bag: look for named inputs and a published rate. This collection is the browse answer for the full range; the sensible default bag inside it is All Purpose 4-4-4.

Useful examples, not a spammy top-ten: garden compost and well-rotted manure (soil builders); seaweed meal (traces and alginates); milled plant meals such as alfalfa or rapeseed (slow nitrogen); animal meals where listed, such as bone meal (phosphorus and calcium — not vegan); and mined minerals such as rock phosphate, polyhalite, gypsum and sulphate of potash. Bagged multi-input blends combine several of those so one application covers N, P, K plus calcium, magnesium, sulphur and traces. Sort by job — soil building, general feed, or a single-nutrient correction — then browse this range rather than chasing a numbered list.

It supplies the major nutrients plants take up as ions, and it feeds the soil life that unlocks them. You get steadier growth and less scorch risk than a harsh soluble feed, plus secondary nutrients many thin NPK bags skip. Organic matter left behind improves structure and water holding over seasons, not overnight. It will not “fix” dead soil in a weekend, it stalls in cold ground, and it will not correct a problem that is waterlogging, drought or root damage. For mixed plots the default bag is All Purpose 4-4-4; crop blends and singles sit beside it in this collection when the job is clearer.

At the root, plants take up the same nutrient ions either way. The real advantage is to the soil: steadier release, less salt spike, organic matter that builds crumb structure over seasons. Trade-offs, stated plainly: slower to act (often 2–6 weeks for granules), a lower and more variable analysis so you apply more by weight, more bulk to store, and almost nothing happens below about 4°C. “Really better” depends on the job — synthetic wins a same-week rescue; organic is the better long-term default for most British gardens. More on the choice at why choose organic fertiliser.

There is no single best bag for planting, home gardens, “all plants”, or a top-ten chart. Compost builds soil; a balanced 4-4-4 feeds generally; a potassium-led blend suits fruiting crops; singles fix deficiencies. Be wary of anything sold as best for everything with no full ingredient list. If you want one default bag from a UK range with every input named, start with All Purpose 4-4-4, then use this collection to browse crop blends and single nutrients when a plant has a clear seasonal job. That is how to choose — not a celebrity ranking.

Work granules into moist soil or compost before planting, or top-dress around growing plants and water in; keep them off leaves and stems; always use the rate on the pack in front of you. On beds, most granular blends sit around every 4–6 weeks in the growing season; pots run out faster (often every 2–4 weeks) because there is less soil and more watering. Granular meals usually start within 2–6 weeks in warm, moist soil and can feed for 6–8 weeks; liquids act in days but fade fast; cold soil stalls everything. Timing detail: how often to apply. A 1.5 kg crop-blend bag is roughly a season for a small greenhouse or raised bed — check each product page.

Yes. Scorch is uncommon at normal garden rates because release is gradual, but too much nitrogen still pushes soft, floppy growth that flowers poorly and attracts aphids. Phosphorus accumulates and is slow to leave soil; surplus potassium can interfere with magnesium and calcium uptake. Modest analyses such as 4-4-4 are harder to overdo than a concentrated extract, which is not a licence to heap it on. Stick to the published rate, water in, and do not reapply after ten days because “nothing happened” — nothing was going to yet.

Garden answers usually split two practical families rather than a tidy textbook pair. First: plant and animal meals and composted matter — proteins and fibres that soil organisms mineralise over weeks (the usual “slow-release organic” bag). Second: mined minerals permitted in organic growing — rock phosphate, sulphate of potash, polyhalite, gypsum — which are not carbon-based but are not synthetic salts either. Coated synthetic pellets are a different tool again, even when the shelf says “slow release”. Meal-based slow release is covered in more depth on our organic slow-release fertiliser notes.

“Natural fertiliser” is the usual synonym in garden centres, and people also say organic plant food or organic feed. Natural is a loose word: it usually means the material is milled, dried, composted or steeped rather than made as a soluble salt — not that it is automatically gentle or certified. Wood ash is natural and will raise pH if you use enough of it. In chemistry, “organic” means carbon-based, which is why some mined minerals sit awkwardly in the word but still belong in organic growing. Browse this collection for named bagged options; compost remains the free bulk answer underneath.

Comfrey liquid is the best-known homemade feed for fruit and flowers (potassium-led); nettle liquid suits leafy growth (nitrogen-led); compost is the best homemade soil feed. Seaweed meal or alfalfa pellets can be steeped as a quicker drench. Coffee grounds: their nitrogen is bound in material that takes months to break down, so as a direct fertiliser they do little — fine on the compost heap. DIY is cheap and variable; it will not match a labelled analysis for a hungry crop in a pot. Soft option when you want a measured bag: All Purpose 4-4-4 in this range.

In British garden folklore, “poor man’s fertiliser” usually means diluted urine — a free nitrogen source if used carefully, heavily diluted, and not treated as a casual spray on salad leaves close to picking. Compost and well-rotted manure are the saner free bulk route for most plots. Neither replaces a bagged blend when you need a known NPK, calcium and traces in a small volume of compost. This collection is for those labelled bags; free soil-builders still belong underneath them.

Home compost and well-rotted manure win on cost per square metre because they use waste you already have and improve structure as well as feeding lightly. Bagged feeds cost more per unit of nutrient than a supermarket soluble, and organic analyses are lower, so you apply more by weight — that is the honest trade. Within a bagged range, buy the analysis and ingredient list you need rather than the cheapest sticker: a thin NPK-only bag can waste a season. Start with compost; add a default bag such as All Purpose 4-4-4 when the crop asks for more.

At farm scale in the UK, fertility still rests on rotations, green manures, livestock manures and composted organic matter, topped up with materials on the organic standards’ permitted list — things like rock phosphate, sulphate of potash, and certain plant or animal by-products where allowed. It is not one miracle bag. Home gardens borrow the same logic at smaller scale: build soil with organic matter, then use named meals and minerals (or a finished blend) for the nutrients compost cannot concentrate. Browse those bagged options here; farm certification rules are stricter than a garden-centre label, so do not assume every garden blend is farm-licence certified.

In agronomy folklore, urea is often nicknamed the “king of fertilizers” because it is a very concentrated nitrogen source (around 46% N). That is a synthetic nitrogen story, not a badge the British garden trade hangs on one organic bag. In the garden, nitrogen, phosphorus and potassium each “rule” different jobs — leaf and stem, roots and flower set, fruiting and hardiness — so the honest answer is to match the nutrient to the plant stage, not chase a royal nickname. For a balanced organic default, use All Purpose 4-4-4; for a single nutrient, browse the nitrogen, phosphorus or potash options in this range.

A blend if you want one bag to cover a crop for the season. Single ingredients if you have a specific deficiency to fix, or you are building your own programme and want to control each element. If you are unsure, start with a blend.

Yes, all of it. Pots, grow bags, raised beds, allotments and open ground.

Two things. The blends are multi-input, so a single bag carries N, P and K plus calcium, magnesium, sulphur and a full trace element set, rather than NPK alone. And every ingredient is named on the label. For a worked comparison against the feeds most people already own, see five UK tomato feeds compared.

Yes. Made with organic ingredients, with no synthetic chemicals, plant protection products or harmful additives.

It depends on the crop and the area, and the rate is on each product page. As a rough guide, a 1.5kg bag of a crop blend covers a season for a small greenhouse or a raised bed.

Granular blends generally go on as growth starts and the soil warms; single minerals when a soil test or the plant tells you something is short. Rates are on every product page, and how often to apply organic fertiliser goes into the timing in more detail.