How do you make comfrey feed?

Pack comfrey leaves into a container, weigh them down, and collect the dark liquid that drains off over a few weeks (or steep leaves in water). Dilute the concentrate about 1:10–1:15 with water before using — it is high in potash, great for tomatoes and fruit.

Is nettle tea good for plants?

Yes — steeping nettles in water for a couple of weeks makes a nitrogen-rich feed good for leafy growth in spring. It smells strong, so dilute it well (about 1:10) and use it on growing crops.

Are banana skins good for the garden?

They contain some potassium, but burying or soaking skins releases very little usefully. They are better chopped into the compost heap, where they break down and feed the soil properly.

Homemade Plant Feeds: Comfrey, Nettle and More

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The short version

Comfrey tea is the star — pack leaves in a lidded bucket, leave 4–6 weeks, dilute the concentrate 1:10–1:15. High in potash, ideal for tomatoes, courgettes and fruiting crops in summer.
Nettle tea for spring leaves — steep young nettle tops 2–3 weeks, dilute about 1:10. Nitrogen-rich, good for young plants and leafy greens early in the season.
Wormery and bokashi liquid are free bonuses — dilute worm liquid around 1:10 and bokashi around 1:100 before watering growing plants.
Wood ash gives a little potash — use sparingly, keep it dry, only from untreated wood, and away from acid-lovers like blueberries.
Skip the folklore feeds — banana skins, coffee grounds and eggshell water all under-deliver; compost them instead, where they actually do good.
Feed properly — only during active growth, never onto dry roots (water first), little and often at weak-tea strength.

You can make genuinely good liquid plant feeds for free, from things growing in your garden or your local hedgerow. Comfrey and nettle teas are the two that really earn their place, and they cost nothing but a little time and patience.

But homemade feeds are also where a lot of garden folklore creeps in. Plenty of the popular tricks — burying banana skins, watering with eggshell soak, scattering coffee grounds — do far less than the internet promises. So here is the honest version: what actually works, how to make it, and what to quietly skip.

This sits within our wider guide to reusing and recycling in the garden, where free materials do real jobs rather than imaginary ones.

Comfrey tea: the best free feed there is

Comfrey is the star of homemade feeding. Its deep roots pull up nutrients — especially potash (potassium) — from well below the surface, and its leaves store them. That makes a comfrey feed high in potassium, which is exactly what fruiting and flowering plants want.

It is brilliant for tomatoes, courgettes, beans, strawberries, chillies and any flowering or fruiting crop. Think of it as a homemade tomato feed, because that is essentially what it is.

How to make comfrey concentrate

There are two methods.

The drained concentrate (best, but smelly). Cut a good armful of comfrey leaves and cram them into a container with a small hole or tap at the bottom — a lidded bucket or a length of drainpipe stood upright both work. Weigh the leaves down with a brick on a plate. Over three to six weeks the leaves rot down and a dark, thick liquid drips out. This concentrate is strong, so you dilute it heavily before use.

The steeped version (easier, even smellier). Pack leaves loosely into a bucket, cover with water, put a lid on, and leave for four to six weeks. Strain off the liquid. This is simpler but produces a properly pungent brew, so keep it well away from the back door.

Fair warning on the smell

Rotting comfrey smells genuinely awful — there is no polite way round it. Use a lid, site the bucket at the bottom of the garden, and you will be fine. The drained-concentrate method smells a little less than the water-steeped one.

How to dilute and use it

The concentrate is too strong to use neat. Dilute it roughly 1 part feed to 10–15 parts water — aim for the colour of weak tea. Water it onto the soil around growing plants every week or two during the main growing season.

Use it from when tomatoes and other fruiting crops start to flower, right through summer cropping. It pairs naturally with growing tomatoes, courgettes and strawberries, all of which respond well to a potash-rich feed once they are setting fruit.

Grow your own supply — and choose Bocking 14

If you plant comfrey, choose the cultivar 'Bocking 14'. Unlike wild comfrey, it is sterile and does not set seed, so it will not spread itself all over the plot — it only grows where you put it. You can cut it several times a season, and it dies back over winter. One small patch in a corner will feed a whole vegetable garden.

Nettle tea: a nitrogen feed for spring

Where comfrey is about potash for fruit, nettles are about nitrogen for leaves. Stinging nettles are rich in nitrogen, which drives green leafy growth — so a nettle feed is most useful in spring and early summer, on young plants and leafy crops getting established.

It suits lettuce and other salad and leafy greens, and gives seedlings and young plants a boost as they put on growth.

How to make it

Wear gloves and cut young nettle tops before they flower (older, seeding nettles are best left out — you do not want to spread the seed). Pack them into a bucket, cover with water, put the lid on, and leave for two to three weeks, stirring occasionally. Strain off the liquid.

Like comfrey, it smells strong, so keep the lid on and the bucket out of the way.

How to use it

Dilute nettle tea about 1:10 — again, weak-tea colour. Water it around leafy crops and young plants every week or two while they are actively growing in spring and early summer.

Comfrey and nettle do different jobs

A simple way to remember it: nettle for leaves in spring, comfrey for fruit in summer. Nitrogen builds the plant; potash helps it flower and fruit. Many growers make a bucket of each and switch over as the season moves on.

Wormery and bokashi liquid

If you run a kitchen-waste system, you may already be producing a free feed without realising it.

A wormery collects a dark liquid in its base — often sold as "worm tea" or leachate. Drain it off, dilute it heavily (around 1:10, until it looks like weak tea), and water it onto growing plants. It is a useful general feed and a tidy way to use a by-product you would otherwise tip away.

A bokashi bin, which ferments kitchen scraps, also produces a liquid you tap off every few days. It is acidic and strong, so dilute it well (roughly 1:100) before watering plants — or simply pour it neat down the drain, where it helps keep pipes clear. Either way it is a bonus, not the main event; the bokashi solids go on to be buried or composted.

Both of these tie in with composting your kitchen waste, which is the real prize — the liquid is just a handy extra.

Wood ash: a little potash, used carefully

Wood ash from a bonfire or untreated firewood contains some potash, plus lime, so in small amounts it can be useful — particularly around fruit and on the compost heap.

But it needs care:

Use it sparingly. It is alkaline (it raises pH like lime), so do not pile it on, and keep it away from acid-loving plants such as blueberries.
Keep it dry until you use it. Rain quickly washes the soluble potash out of ash left in a heap outdoors, leaving you with not much. Store it somewhere dry and apply a light scattering.
Only burnt wood and paper. Never use ash from coal, painted or treated timber, or anything with plastics or chemicals in it.

A light dusting around gooseberries and currants, or a sprinkle into the compost, is the sensible scale. It is a minor helper, not a main feed.

The honest myth-checks

Now the part the internet gets wrong. These three are everywhere, and they all under-deliver.

Banana skins

The claim: banana skins are packed with potassium, so bury them by your tomatoes or soak them in water for an instant feed.

The reality: banana skins do contain some potassium, but burying a whole skin or soaking one in water releases very little of it in any useful, available form. A soggy skin sitting in the soil mostly just sits there, and "banana water" is weak stuff. Worse, buried scraps can attract flies or vermin.

The better answer is simple: chop them into the compost heap. There they break down properly along with everything else, and the nutrients end up in finished compost that genuinely feeds your soil. Composting is where banana skins do real good.

Coffee grounds

The claims are everywhere: coffee grounds are a great fertiliser, they make a slug barrier, they acidify the soil for your blueberries.

The honest picture:

As a fertiliser, used coffee grounds are mostly spent — the brewing has already pulled a lot out — and what nitrogen remains is locked up as the grounds break down. Scattered thickly they can even cake and repel water.
As a slug barrier, the popular claim does not hold up. Tests have repeatedly failed to show grounds reliably stopping slugs and snails; it is one of those tips that sounds plausible and simply does not work in the garden.
As a soil acidifier, used grounds are close to neutral, not the strong acid people imagine.

So treat coffee grounds the same way as banana skins: add them to the compost heap, where they are a perfectly good "green" ingredient in moderation. That is the use that actually stands up.

Eggshell water

The trick: soak crushed eggshells in water and use the "calcium water" as a feed, or to fix problems like blossom end rot.

The reality: the amount of calcium that dissolves out of eggshell in water is negligible. Eggshell is calcium carbonate, which barely dissolves — the water you pour off carries almost nothing useful, and crushed shells in the soil break down extremely slowly too.

Crucially, eggshells do not cure blossom end rot. That problem is about the plant's inability to move calcium to the fruit, usually caused by uneven watering — not a shortage of calcium in the soil. Adding eggshell does nothing for it; consistent watering does. We cover this properly in our guide to using eggshells in the garden, and the real causes in blossom end rot.

If you have eggshells, the best home for them is — yes — the compost heap, where they slowly add a little mineral content over time.

The pattern here

Notice the theme: banana skins, coffee grounds and eggshells are all real materials with a sliver of truth behind the hype — but the magic-feed versions do not work. In every case, composting them is the honest, effective answer.

How and when to feed

A good homemade feed only helps if you apply it sensibly. A few rules cover almost everything.

Feed during active growth. Liquid feeds are for the growing season — roughly late spring through summer — when plants are putting on growth, flowering and fruiting. There is little point feeding dormant plants in winter.
Never feed onto dry roots. Feeding bone-dry compost can scorch roots and the feed runs straight through. Water first, then feed, or water the diluted feed in well. This matters most for pots and grow bags, which dry out fast.
Dilute properly. Comfrey concentrate 1:10–1:15, nettle and worm liquid around 1:10, bokashi liquid around 1:100. Weak-tea colour is a safe rule of thumb — too strong does more harm than good.
Feed little and often. A weak feed every week or two beats an occasional heavy dose.
Match the feed to the job. Nitrogen-rich nettle for leafy growth and young plants in spring; potash-rich comfrey for flowering and fruiting crops in summer.

Container plants need feeding most, because they quickly use up the nutrients in their compost — see growing food in containers for how often.

And remember that liquid feeds are a top-up, not a foundation. The real engine of healthy plants is good soil, built with home-made compost and a steady habit of improving your soil. Feeds give a seasonal boost; the soil does the heavy lifting.

If you want a comfrey patch of your own — the only kit worth buying for any of this — a few 'Bocking 14' crowns will pay for themselves many times over.

For more free-and-honest ideas across the whole garden, head back to reuse and recycle in the garden, or browse the wider getting started guides.