How Garlic Peels Can Feed Plants and Deter Pests

Across Europe and North America, households discard kilos of edible food scraps each year, even as balcony and garden soil gradually becomes depleted. With food costs increasing, small-scale home growing returning to favour and distrust of synthetic products rising, many people want solutions that are both useful and inexpensive.

Turning kitchen waste into a plant booster

Italian researchers and city gardeners have focused on an item that is usually thrown away without thought: garlic peels. These 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 trials undertaken at the University of Bologna from 2021 to 2023, involving potted herbs and ornamental plants, indicate that this straightforward infusion may modestly promote growth. 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 be particularly relevant for households trying to make every pound or euro go further. Keeping garlic peels steeping in a jar costs nothing, creates no additional packaging and can replace part of a household's fertiliser spending. It also supports a broader move towards more circular routines at home: less waste, more reuse and fewer externally purchased inputs.

How to make garlic peels into liquid fertiliser

The technique promoted by Italian gardening groups is remarkably uncomplicated, helping to 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 substantial 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 it loosely, then leave at room temperature for 24 to 48 hours.
• Strain the mixture, compost the peels and water plants with the infusion once each week.

According to tests cited by Italian horticultural associations, ornamental and aromatic plants watered with this mixture achieved an average 12% increase in leaf density against control plants. It will not transform basil on a windowsill into a jungle, but over several weeks it may improve foliage and 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 in the pot

Although the process remains under investigation, agronomists identify two principal effects. Firstly, the infusion supplies a mild blend of nutrients and organic compounds. It cannot offer the accuracy of a commercial NPK fertiliser, but it may stimulate microbial activity in potting compost, allowing roots to reach minerals already available in the growing medium.

Secondly, the sulphur compounds associated with garlic seem to affect certain soft-bodied insects and mites. Peel water contains far lower concentrations than garlic-oil sprays, but regular application appears to make conditions less appealing to many pests.

Garlic peels as a quiet pest deterrent

Urban gardeners in northern Italy, who track pests on balconies and rooftop growing beds, have noted a consistent pattern. In over 60% of their recorded cases, plants regularly watered with garlic-peel infusion had fewer aphids and spider mites than untreated plants growing under comparable conditions.

It is not a contact insecticide, but rather acts as a background deterrent. The faint garlic aroma remaining in the soil and around leaves seems to disorient or repel insects looking for a suitable host. Some UK allotment holders now pair it with netting and companion planting, particularly for soft herbs and lettuces that commonly draw sap-feeding pests.

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

For households reluctant to spray chemicals in compact indoor areas, this is significant. Watering plants with an infusion made from an everyday cooking ingredient can seem less worrying than using a brightly coloured product carrying warning labels, especially where children and pets are present.

How often to use it and which plants suit it

Researchers at CREA, Italy's national agricultural research council, advise gardeners not to overuse garlic infusion. It can be beneficial in moderation, but frequent applications at high strength may upset the balance of potting compost, particularly for sensitive plants.

Suggested frequency	Best-suited plants	Notes
Once a week	Culinary herbs, leafy vegetables (lettuce, spinach, chard)	Supports root strength and leaf regrowth
Every 10–14 days	Flowering plants (geranium, petunia, balcony mixes)	Skip during peak flowering if plants show stress
Avoid frequent use	Acid-loving plants (azalea, blueberry, some ferns, orchids)	Risk of gradual pH shift in the substrate

Anyone wishing to try the technique on delicate plants should begin cautiously: use a half-strength infusion once a month on only one or two pots, and retain other plants as controls. Changes in leaf colour, growth speed or root condition over several weeks can offer a practical guide to whether treatment should continue.

Signs to stop treatment

• Ongoing yellowing in young leaves that cannot be attributed to overwatering.
• A white crust appearing on the compost surface despite using soft water.
• A distinct unpleasant odour from the pot, suggesting anaerobic conditions.

Pausing garlic-infusion use and flushing the container with clean water will generally restore the balance. For some worn-out pots, repotting into fresh compost can give the container a new lease of life.

Reducing costs and food waste

At household level, this may appear to be a small change. Across an entire city, however, the combined impact can become meaningful. Italian figures indicate that households with a compact urban garden or numerous balcony pots may reduce annual fertiliser costs by around 5% by using garlic peels alongside other homemade feeds.

Meanwhile, every handful of skins used to nourish plants rather than being binned lowers the amount of organic waste municipal services must process. The reduction may initially seem negligible, yet analysts associate it with reduced transport emissions and less demand on waste-treatment facilities. At a time of rising food and energy prices, every resource loop completed within the home can carry strategic importance.

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 is seldom enough to meet all a plant's nutritional needs, especially in containers where nutrients are quickly washed away. As a result, many gardeners use it as one part of a broader homemade fertiliser toolkit. Coffee grounds, crushed eggshells and banana skins provide different nutrients and textures when applied carefully.

• Coffee grounds: a light nitrogen addition, ideally composted or blended into soil in small quantities.
• Eggshells: a slow-release calcium source when dried and crushed finely.
• Banana skins: provide potassium and are frequently steeped in water in the same way as garlic peels.

Alternating these feeds over the growing season can help prevent nutrient imbalances. One month of garlic infusion, followed by another using a weak compost tea, then a period with clean water alone, brings variety without overloading sensitive root systems.

Risks, limits and realistic expectations

Garlic peels cannot transform exhausted soil into a productive field, nor can they replace quality compost, sufficiently sized pots or dependable watering. Relying too heavily on one homemade mixture may conceal more fundamental problems, including depleted compost or persistent underwatering.

There is also a limited risk of adding too much organic material in enclosed indoor settings. Garlic skins left steeping too long in warm conditions can ferment, creating strong smells that linger in rooms. Keeping infusion periods shorter and using the liquid promptly helps to minimise this issue.

For people in very limited spaces, including flat residents in London or New York, garlic peels can provide an introduction to more ambitious circular gardening practices. Once people become accustomed to turning scraps into something useful, many go on to try balcony composting, worm bins or shared local compost hubs. That approach can then extend to collecting water, saving seeds and sharing tools.

As food systems respond to climate shocks and geopolitical tensions, modest low-tech household actions can matter more than their scale implies. A reused glass jar on the kitchen counter, holding garlic skins rather than stale water, becomes one of many understated, practical experiments that can make homes slightly more self-reliant and plants somewhat more resilient.