How Garlic Peels Make a Liquid Fertiliser for Plants

Across Europe and North America, households discard kilos of edible food scraps each year, even as balconies and gardens contend with depleted soil. With food bills increasing, small-scale home growing making a comeback and distrust of synthetic products rising, many people want solutions that are useful as well as inexpensive.

Turning kitchen waste into a plant booster

Italian researchers and city gardeners have turned their attention to an item that is usually thrown away without thought: garlic peels. The papery, translucent skins contain sulphur compounds, natural antioxidants and trace quantities of minerals. Left in water for one or two days, some of these components seep into the liquid, ready to be added to a watering can.

Research conducted by the University of Bologna from 2021 to 2023 on potted herbs and ornamental plants indicates that this basic infusion may give growth a modest lift. On average, plants given garlic-peel water developed denser foliage than those watered only with tap water.

What usually lands in the food waste caddy can act as a free liquid feed and a mild shield against pests.

This can make a difference for households trying to make every pound or euro go further. Keeping garlic peels steeping in a jar costs nothing, creates no extra packaging and can cover at least some of the usual fertiliser expense. It also reflects a broader move towards circular habits in the home: less going into the bin, more being reused and fewer bought-in inputs.

How to make garlic peels into a liquid fertiliser

The technique promoted by Italian gardening communities is remarkably straightforward, which helps explain why it has spread so quickly across social media.

Basic garlic-peel infusion recipe

• Save the dry skins from three garlic cloves, taking out any larger pieces of garlic flesh.
• Put the skins into a clean glass jar or jug.
• Add one litre of non-chlorinated water, either filtered or left standing overnight.
• Cover the container loosely and keep it at room temperature for 24 to 48 hours.
• Strain the mixture, compost the peels and use the resulting infusion to water plants once weekly.

According to trials cited by Italian horticultural associations, ornamental and aromatic plants watered with the solution recorded an average 12% increase in leaf density compared with control plants. It will not transform basil on a windowsill into a jungle, but over several weeks it may improve foliage and encourage root activity.

One litre of garlic-peel infusion per week, used consistently over a season, can support a small balcony garden without buying bottled fertilizer.

What happens inside the pot

The exact process remains under investigation, although agronomists point to two principal effects. Firstly, the infusion provides a mild mix of nutrients and organic compounds. It cannot offer the precision of a commercial NPK fertiliser, but it may stimulate microbial activity in the potting compost, helping roots obtain minerals that are already available.

Secondly, the sulphur compounds associated with garlic seem to place pressure on certain soft-bodied insects and mites. Peel water contains these compounds at far lower concentrations than garlic-oil sprays, but repeated applications appear to make conditions less attractive to many pests.

Garlic peels as a discreet ally against pests

City gardeners in northern Italy who track pests on balconies and rooftop planters have observed a distinct pattern. In over 60% of recorded cases, plants regularly watered with garlic-peel infusion had fewer aphids and spider mites than untreated neighbouring plants growing in similar conditions.

It is not a contact insecticide. Instead, it works more as an ongoing deterrent. The faint garlic odour remaining in the compost and around the leaves seems to disrupt or discourage insects looking for host plants. Some UK allotment holders now pair it with netting and companion planting, particularly for tender herbs and lettuces that often draw sap-feeding pests.

Garlic peel water will not “cure” a heavy infestation, but it may slow outbreaks before they explode.

That distinction is important to people reluctant to spray chemicals in compact indoor areas. A watering can containing an infusion made from a familiar cooking ingredient can feel less concerning than a brightly coloured container covered with warning labels, particularly in homes with children or pets.

How often to use garlic-peel fertiliser and on which plants

Researchers at CREA, Italy’s national agricultural research council, advise gardeners not to overuse it. Garlic infusion can be beneficial in moderation, but frequent applications at strong concentrations may upset the balance of potting compost, especially for sensitive plants.

Anyone wishing to trial the approach on sensitive plants should begin cautiously: use a half-strength infusion once a month on only one or two pots, while leaving comparable specimens untreated as controls. After several weeks, changes in leaf colour, growth speed or root condition can provide a useful guide to whether treatment should continue.

Signs that treatment should be stopped

• Young leaves keep turning yellow for reasons unrelated to overwatering.
• A white crust develops on the compost surface despite using soft water.
• The pot gives off a clear unpleasant smell, signalling anaerobic conditions.

In most cases, stopping the garlic infusion and flushing the container with clean water will restore the balance. For especially tired pots, repotting into fresh compost can give the container a new lease of life.

Reducing costs and food waste

For an individual household, this may seem like a small adjustment. Across an entire city, however, the combined impact becomes more meaningful. Italian figures indicate that families with a compact urban garden or a balcony planted with pots could reduce annual fertiliser costs by around 5% by partly using garlic peels and other homemade feeds.

Each handful of peel used on plants rather than sent to the bin also lowers the amount of organic waste municipal services must process. The initial reduction is slight, but analysts associate it with reduced transport emissions and less strain on treatment infrastructure. At a time of rising food and energy prices, every household loop that can be closed carries strategic value.

What used to be a silent journey from chopping board to bin becomes a micro-cycle: kitchen offcuts return as nutrients, not rubbish.

Combining garlic peels with other simple fertilisers

Garlic infusion will rarely meet every nutritional need of plants, particularly in containers where nutrients are quickly washed away. Many gardeners therefore use it as one element of a broader homemade toolkit. Coffee grounds, crushed eggshells and banana skins each add different nutrients and textures when applied carefully.

• Coffee grounds: provide a light nitrogen boost and are best composted or incorporated into soil in small quantities.
• Eggshells: offer slow-release calcium once dried and finely crushed.
• Banana skins: supply potassium and are often steeped in water in the same way as garlic peels.

Alternating these feeds during the growing season can help prevent imbalances. One month of garlic infusion, followed by another using a weak compost tea, then a period of plain water only, creates variety without placing delicate root systems under too much pressure.

Risks, limits and sensible expectations

Garlic peels will not turn poor compost into a high-yielding plot, nor can they replace quality compost, sufficiently large pots or regular watering. Depending too heavily on any one homemade treatment can conceal more serious underlying problems, including worn-out soil or persistent underwatering.

There is also a limited risk of adding too much organic matter in enclosed indoor settings. Garlic skins left steeping too long in warm conditions may ferment, creating strong odours that linger in a room. Keeping infusion times short and using the liquid promptly reduces this effect.

For people with very limited room, including flat residents in London or New York, garlic peels can be an introduction to more ambitious circular gardening practices. Once people become used to turning kitchen scraps into something useful, many progress to balcony composting, worm bins or shared local compost hubs. The same way of thinking can then extend to collecting water, saving seeds and sharing tools.

As food systems respond to climate shocks and geopolitical tensions, small low-tech household actions can matter more than their scale would suggest. A reused glass jar on the worktop, holding garlic skins rather than stale water, becomes one of many quiet and practical experiments that can make homes slightly more self-reliant and plants a little more robust.