Garlic Peel Fertilizer for Plants: What Science Supports and How to Use It

Garlic peels are often promoted online as a homemade fertilizer for houseplants and gardens, but the evidence is more nuanced than many gardening recipes suggest.

Recent research does support using garlic peel as an organic soil amendment. In a 2025 study published in Scientific Reports, soil amended with garlic peel showed substantially higher water-holding capacity, while rice seedlings grown under water stress performed better than untreated stressed plants.

That does not mean garlic peel is a complete fertilizer or that every popular garlic-water recipe has been scientifically tested. The most evidence-supported use is as organic material added to soil or compost, rather than as a replacement for a balanced fertilizer.

Table of Contents

Is garlic peel good for plants?

Potentially, yes — particularly as a soil amendment.

Researchers have found that garlic peel contains large amounts of structural fiber as well as phenolic compounds, proteins, minerals and other plant-derived compounds. A recent Scientific Reports study found that garlic peel had the highest fiber content among the Allium peels tested and that adding it to soil improved water retention.

In the same experiment, rice seedlings grown under water-limited conditions performed better when garlic peel was incorporated into the soil. The researchers observed improvements in plant growth, hydration and several physiological indicators compared with water-stressed plants grown without the amendment.

These results are promising, but they came from a controlled rice experiment. They should not be interpreted as proof that garlic peel will produce the same response in every vegetable, flower or houseplant.

What does science actually show?

Garlic peel is not especially rich in sulfur

One widespread claim is that garlic peel is valuable mainly because it is exceptionally rich in sulfur. Recent measurements complicate that idea.

In the Scientific Reports study comparing garlic, red onion and yellow onion peels, garlic peel contained the lowest measured sulfur concentration of the materials tested.

Garlic peel still contains useful organic material and nutrients, but describing it primarily as a “sulfur-rich fertilizer” overstates the available evidence.

Its high fiber content may actually be one of its more interesting soil benefits. Researchers linked fiber content with improved soil water-holding capacity after Allium peel amendments were added.

Garlic peel may improve soil water-holding capacity

Water retention is where the research becomes particularly interesting.

The 2025 study evaluated garlic and onion peels as amendments under restricted irrigation. Garlic peel had the highest crude-fiber content among the materials analyzed, and soil containing garlic peel showed a substantial increase in water-holding capacity compared with untreated soil.

That could make agricultural and food-processing waste more useful as a soil-conditioning material, particularly in sandy soils or other growing media where moisture retention is limited.

However, the experiment was conducted under controlled conditions. Garden soils vary greatly in texture, organic-matter content, drainage and microbial activity, so the effect in a home garden may be smaller or different.

Can garlic peel actually increase plant growth?

In the same controlled experiment, rice seedlings grown under water stress responded positively to garlic-peel-amended soil.

Researchers reported increases in shoot growth, fresh weight and chlorophyll measurements compared with the water-stressed control group. Plants also showed improved water status and lower indicators of oxidative stress.

The study suggests that garlic peel may function as more than a source of mineral nutrients. Its fiber and bioactive compounds may also change the physical and biological environment around plant roots.

For gardeners, however, the practical takeaway should remain conservative: garlic peel can be a useful source of organic matter, but it has not been demonstrated to outperform conventional compost or properly formulated fertilizers across common garden crops.

Does garlic peel contain antifungal compounds?

Garlic peel does contain biologically active compounds.

A separate peer-reviewed study examining garlic peel tissues found proteins and metabolites associated with plant defense. Garlic peel extracts also inhibited germination of Fusarium oxysporum spores under laboratory conditions.

That finding is scientifically interesting, but it does not establish garlic peel as a proven fungicide for gardens.

Laboratory inhibition of a pathogen is very different from controlling fungal disease on tomatoes, roses or other plants outdoors. Concentration, environmental exposure, formulation and plant sensitivity all affect whether an antimicrobial compound works in practice.

What is the best way to use garlic peel in the garden?

Based on the available evidence, the safest and most defensible methods are the simplest ones: composting the peels or incorporating modest amounts of them into organic soil amendments.

1. Add garlic peel to compost

This is the easiest option.

Dry garlic skins can be mixed with other kitchen and garden waste in a compost pile or bin. Once decomposed, the resulting compost provides a much broader nutrient profile than garlic peel alone.

Garlic skins are dry and carbon-rich, so they should be mixed with wetter, nitrogen-rich materials such as grass clippings or fresh plant waste rather than forming a thick layer by themselves.

2. Use small amounts as a soil amendment

Dry peels can also be broken into smaller pieces and mixed into soil before planting.

This is closer to the method tested in the scientific literature than many homemade liquid recipes. Decomposition adds organic material to the soil and may influence water retention and microbial activity.

Do not bury large compacted masses of fresh organic material immediately around young roots. Organic residues need oxygen and time to decompose, and excessive undecomposed material can temporarily alter local soil conditions.

3. Use garlic-peel water cautiously

Garlic-peel water is extremely popular in gardening videos and social-media posts, usually made by soaking garlic skins in water for several hours or days.

There is a plausible reason why water extracts may contain soluble compounds from the peel. However, there is currently not enough evidence to establish a scientifically validated concentration, soaking time or application frequency for garlic-peel fertilizer water.

If gardeners choose to experiment with it, it should be treated as a mild supplemental amendment rather than a primary fertilizer.

Avoid assuming that a stronger-smelling or more concentrated solution is better. Concentrated plant extracts can contain biologically active compounds, and plant sensitivity varies between species.

Should you spray garlic-peel water on leaves?

There is currently insufficient evidence to recommend routine foliar application of homemade garlic-peel extracts as a fertilizer.

Nutrients applied to leaves must be present in soluble forms and appropriate concentrations to be absorbed effectively. Homemade extracts are not standardized, which means their nutrient content and chemical strength are unknown.

For this reason, soil or compost applications are easier to justify than repeated foliar spraying.

Can garlic peel replace regular fertilizer?

No.

Garlic peel is an organic amendment, not a balanced N-P-K fertilizer.

Plants require nitrogen, phosphorus, potassium and multiple secondary and micronutrients in amounts that change with crop type, soil fertility and growth stage.

A handful of kitchen scraps cannot reliably provide those nutrients at predictable rates.

For plants with known nutrient deficiencies or heavy-feeding crops such as tomatoes, corn or container vegetables, base fertilization decisions on soil conditions and a fertilizer with a known nutrient analysis.

Garlic peel vs. other kitchen scraps

The common theme is that kitchen scraps generally perform better as components of a composting or soil-building system than as precise substitutes for commercial fertilizers.

Which plants can use garlic peel?

There is not enough research to create a scientifically supported list of crops that specifically “prefer” garlic peel fertilizer.

Most garden soils can accept small quantities of decomposed plant material, so garlic skins can generally be composted for use around vegetables, ornamental plants, herbs and flowers.

That is different from claiming that tomatoes, peppers, roses or brassicas have a special response to garlic peel. Crop-specific benefits have not been adequately demonstrated.

When should you avoid using garlic peel?

• Do not use moldy or rotting peels in homemade liquid extracts.
• Do not apply thick layers that can mat together and reduce airflow at the soil surface.
• Do not rely on garlic peel to correct a diagnosed nutrient deficiency.
• Do not treat homemade garlic extracts as registered pesticides or fungicides.
• Do not assume that a concentrated extract is safe for foliar spraying.

What the newest research changes

The most interesting development since this article was originally published is new experimental evidence showing that garlic peel can affect soil physical properties and plant performance under water stress.

The research strengthens the case for treating garlic peel as a potentially useful agricultural waste material.

At the same time, it weakens some of the exaggerated claims commonly made online. The evidence currently supports soil amendment and waste-recycling applications much more strongly than precise homemade fertilizer recipes, pest-control claims or crop-specific feeding programs.

Frequently asked questions

Sources: Scientific Reports, MDPI, PubMed