Natural Fertilisers: What Works, What Does Not, and What You Can Make

Search for homemade plant food and you will find eggshells, coffee grounds, banana peel and comfrey recommended in the same paragraph, as though they were equivalent. They are not. Some homemade feeds have real substance behind them; several of the most-repeated ones are essentially folklore, and mixing the two makes it impossible to know what is worth your time.

This guide sorts them honestly. But it starts with a distinction that matters more than any individual recipe: feeding the soil and feeding the plant are different jobs, and knowing which one you are doing determines whether feeding is necessary at all.

Soil Feeding vs Plant Feeding

The FAQ sets it out; here is the practical consequence:

Improve the soil first, and feed directly only where the soil cannot do the job. Repeatedly liquid-feeding a border is treating a symptom of poor soil; a mulch of compost each year is the actual fix, which is the position the no-dig, mulching and soil guides all take.

The Feeds That Genuinely Work

Comfrey and nettle liquid feeds

The two homemade feeds with real substance, and both are free. Comfrey is deep-rooted and accumulates potassium in its leaves, making comfrey feed a reasonable homemade equivalent of the high-potash feeds the tomato, pepper and fruit guides recommend at flowering. Nettles are relatively high in nitrogen, better suited to leafy growth earlier in the season.

1. Pack leaves into a container — a lidded bucket or barrel.
2. Either add water (roughly filling the container) or weigh the leaves down and let them rot without water, which yields a more concentrated and considerably less pungent liquid.
3. Cover and leave for several weeks.
4. Dilute heavily before use — to about weak-tea colour for the watered version, much more for the concentrate.
5. Site it away from doors and windows. The smell is genuinely bad and is the main practical objection.

A comfrey patch in a corner is one of the more useful things a garden can host: cut several times a season, it supplies feed material, compost activator and mulch. Choose a non-seeding variety if you do not want it spreading.

Compost, manure and leaf mould

• Garden compost — the backbone. Improves soil and supplies nutrients gradually. The compost bin and worm bin guides cover making it.
• Worm castings — richer and more concentrated than ordinary compost, excellent as a potting booster and top-dressing, and the liquid drainings dilute into a good feed.
• Well-rotted manure — a strong soil improver. Must be well rotted: fresh manure scorches roots and can carry weed seeds. Ask about the source, since manure from land treated with certain persistent herbicides has caused serious problems for gardeners.
• Leaf mould — low in nutrients but exceptional for structure, per its own guide. A conditioner rather than a feed.
• Green manures — crops grown to be dug in or cut down, adding organic matter and, in the case of legumes, nitrogen.

Bought organic fertilisers

Where a genuine nutrient boost is needed, organic options work well and are worth knowing: seaweed feeds and biostimulants, pelleted poultry manure as a general-purpose feed, bone and blood-based products for specific nutrients, and rock-based minerals for slower release. They are not free, but they are effective and honest about what they contain — which is more than can be said for some homemade suggestions.

Understanding What Fertiliser Labels Mean

Fertiliser packaging carries three numbers, usually shown as N-P-K, and knowing what they mean makes every feeding decision easier. N is nitrogen, which drives leafy green growth — the right emphasis early in the season and for leafy crops, and the wrong one later, since excess nitrogen produces soft sappy growth that attracts aphids and delays flowering and fruiting. P is phosphorus, associated with root development and establishment. K is potassium (potash), which supports flowering, fruiting and general hardiness — the reason tomato feed is high in it and the reason comfrey is worth making. A balanced general feed carries roughly even numbers; a tomato or fruit feed is weighted heavily toward K; a lawn feed is usually weighted toward N. Beyond the big three, fertilisers may list trace elements, which matter in small quantities and are usually supplied adequately by compost and organic matter in a well-managed soil. Reading those three numbers tells you what a product is actually for, regardless of what the marketing on the front says.

Feeding Different Plants

The Ones That Do Not Work

The FAQ covers the main offenders; the full sorting:

The consistent thread: most of these are perfectly good compost ingredients and poor direct fertilisers. Route them through the heap or the worm bin, where they break down properly, and you get the benefit in usable form.

Signs of Over-Feeding

Under-feeding is visible and easily fixed; over-feeding is subtler and does more damage, so it is worth recognising. The signs: lush, dark, soft growth with few flowers or fruit, which means too much nitrogen and is the commonest form; aphid infestations concentrating on that soft sappy growth, since it is exactly what they prefer; scorched leaf edges or a white crust on compost surfaces and pot rims, indicating salt build-up from concentrated or over-frequent feeding; sudden wilting after feeding, which can mean root scorch; and plants that grow tall and floppy and then need staking they should not have needed. The remedy for salt build-up in containers is to flush the pot thoroughly with plain water, and thereafter to feed at the recommended dilution rather than by generosity. In beds, simply stop feeding and let the soil balance out — established plants in decent soil recover quickly once left alone.

When and How Much to Feed

• Containers need it most — compost nutrients run out within weeks, so weekly liquid feeding through the growing season is standard, as every container guide on this site repeats.
• Switch to high potash at flowering for fruiting and flowering plants — the tomato feed principle, and where comfrey earns its place.
• Nitrogen early, potash later. Nitrogen builds leaves; potash builds flowers and fruit. Feeding nitrogen all season gives you a large green plant with little crop.
• Stop feeding in late summer for perennials, shrubs and roses, since soft late growth is what frost damages — the rose and frost guides both make this point.
• Do not feed a stressed plant. Fertiliser on damaged roots or a drought-stressed plant adds injury, and the diagnosis guide's sequence — water, light, roots — comes first.
• Follow dilution rates. More is not better; over-concentrated feed scorches roots and leaves.
• Water before feeding, not onto dry compost, for the same reason.

Making Compost Tea, Honestly

Compost tea — steeping finished compost or worm castings in water and applying the liquid — is widely promoted, and deserves a measured assessment. As a mild liquid feed it is perfectly reasonable: it delivers some soluble nutrients and is a sensible use of the drainings from a worm bin, which the worm composting guide already recommends diluting and using. The stronger claims made for actively aerated versions, involving pumps and added sugars to multiply microorganisms, are less settled, and a poorly made brew can go anaerobic and smell foul. The practical position: if you have a worm bin, dilute and use the liquid, because it is free and mildly useful. If you want to steep some compost in a bucket of water for a week and water plants with it, that is fine too. But treat it as a supplement rather than a replacement for actually spreading compost on the soil, which delivers far more benefit for far less effort.

The Sustainability Case

Beyond cost, there is a reasonable environmental argument for this approach. Synthetic fertiliser manufacture is energy-intensive, and nutrients washed out of over-fed gardens contribute to water pollution. A garden run on compost, mulch, homemade feeds and targeted organic fertiliser closes more of its own loops: kitchen and garden waste becomes compost, comfrey and nettles become feed, autumn leaves become leaf mould, and the soil holds more of what it is given rather than leaching it. That is the same principle the reduce-plastic, food-waste and rainwater guides all follow — use what you already have, and stop the outputs leaving. It is also, usefully, the cheaper option in every case.

The Classic Mistakes

1. Feeding plants when the soil needed improving — treating the symptom.
2. Nitrogen all season, producing leaves instead of flowers and fruit.
3. Over-concentrated feeds that scorch roots.
4. Feeding a plant whose actual problem is water, light or root damage.
5. Scattering eggshells and banana peel and considering the plant fed.
6. Fresh manure applied without rotting.
7. Feeding late in the season and inviting frost damage on soft growth.

The Bottom Line

Get the distinction right first: feed the soil with compost, manure, leaf mould and mulch, and it will feed most plants in open ground without further help. Reserve direct feeding for the situations where the soil genuinely cannot deliver — containers, baskets and heavy croppers — and use it deliberately, with nitrogen early and potash once flowering starts, stopping in late summer. Make comfrey and nettle feeds if you have the space, because they work and cost nothing; buy organic fertiliser where you need something specific. And route the eggshells, coffee grounds and banana peel through the compost heap rather than around the base of a plant, where they achieve very little except the feeling of having done something.