Legionnaires’ disease is often associated with large buildings, air-conditioning systems or contaminated water sources — but did you know some common gardening products can also carry the bacteria that causes it?

In Australia, health authorities have long warned that Legionella bacteria can be present in certain soil-based and organic gardening materials, particularly when they’re dry, dusty or poorly stored. Activities as simple as opening a bag of potting mix, turning compost, or spreading mulch can release fine particles into the air, creating an unexpected exposure risk.

This doesn’t mean gardening is unsafe — far from it. But understanding where the risks can occur, and how simple handling and hygiene measures can reduce them, helps you garden with confidence. In this article, we’ll explore some of the most common gardening products linked to Legionnaires’ disease, why they can pose a risk, and what you can do to protect yourself while enjoying time in the garden.

Quick refresher: What is Legionnaires’ disease?

Legionnaires’ disease is a serious type of pneumonia caused by Legionella bacteria. These bacteria occur naturally in the environment and can grow in warm, moist conditions. People become infected by breathing in tiny droplets or dust particles contaminated with the bacteria — not through person-to-person contact.

Symptoms often begin with flu-like signs, such as fever, chills, headache and muscle aches, and can progress to cough, shortness of breath and chest pain as the lungs become affected. Because symptoms can worsen quickly, Legionnaires’ disease usually requires medical treatment and hospital care.

Not everyone exposed to Legionella will become ill. The risk is higher for older adults, smokers or ex-smokers, and people with chronic lung disease or weakened immune systems. Understanding how the bacteria are transmitted helps explain why certain gardening activities — particularly those that create dust or aerosols — can sometimes increase the risk of exposure.

How Legionella can be present in gardening products

Legionella bacteria occur naturally in the environment and can survive in soil, compost and water, particularly when conditions allow them to multiply. In gardening products, the risk isn’t usually the presence of bacteria alone, but how the product is stored, handled and disturbed.

Many gardening materials are made from organic matter, such as bark, wood chips, composted plant material and soil. When these materials are kept warm and moist, they can support the growth of a wide range of microorganisms — including Legionella. Poor ventilation, sealed packaging and prolonged storage can further encourage bacterial growth.

The risk increases when gardening products dry out and become dusty. Opening bags of potting mix, tipping mulch, or turning compost can release fine particles into the air. If these particles contain Legionella, they can be inhaled, which is how infection occurs.

Water can also play a role. Stagnant water in hoses, watering systems or water features can allow bacteria to multiply, especially in warm weather. When water is sprayed or aerosolised, it can create tiny droplets that are easily breathed in.

Now, let’s have a look at the list of common gardening products that can increase the risk of Legionnaires’ disease.

Common gardening products linked to Legionella exposure

While Legionella bacteria can occur naturally in the environment, certain gardening products and materials are more likely to pose a risk — particularly when they are dry, dusty, moist for long periods, or disturbed during use. Below are some of the most commonly recognised sources linked to exposure during gardening.

1. Potting mix and potting soil

Potting mix is one of the most well-recognised gardening products linked to Legionella exposure in Australia. It’s commonly made from composted organic materials such as pine bark, wood products, sawdust and other plant matter, which can support bacterial growth under the right conditions.

Examples of situations where exposure risk may increase include:

Opening a new bag of dry potting mix, especially if dust is released into the air
Pouring potting mix into pots or garden beds at face level
Working with potting mix in enclosed or poorly ventilated areas, such as sheds or garages
Handling old or partially used bags that have been stored in warm conditions

2. Compost (commercial or home-made)

Compost creates a warm, nutrient-rich environment that can support bacterial growth, including Legionella, particularly when it’s moist, compacted or poorly aerated.

Examples and higher-risk situations include:

Home compost bins or heaps, especially when turned or mixed
Commercial compost used for vegetable gardens or landscaping
Manure-based composts or compost blends with organic waste
Dry compost that becomes dusty when disturbed
Old compost piles that have been sitting for long periods

3. Mulch (Including backyard mulch)

Mulch is made from organic materials and can support microbial growth depending on its composition, moisture level and storage conditions. Mulch can become a concern when it’s stored in warm, moist conditions and later disturbed or allowed to dry out, creating dust.

Examples of mulch types linked to higher risk include:

Wood chip mulch
Bark mulch
Sugarcane mulch
Pine bark or forest mulch
Stored backyard mulch piles, particularly if damp and compacted

4. Garden soil, soil improvers and conditioners

Soil-based products vary widely, but risk can increase when materials are dry, fine or heavily organic.

Examples include:

Bagged garden soil
Soil improvers and conditioners
Organic blends enriched with compost or manure
Seed-raising mixes
Reused or old soil stored in bags or containers

5. Water sources, hoses and irrigation equipment

Legionella can also multiply in stagnant or warm water, making certain garden water systems a potential source of exposure.

Examples include:

Garden hoses, especially those left full of water in warm weather
Sprinklers and irrigation systems that aren’t used regularly
Drip irrigation lines with standing water
Decorative water features, ponds or fountains
Rainwater tanks connected to garden systems

The risk increases when water is sprayed or aerosolised, creating fine droplets that can be inhaled.

Simple steps to reduce risk while gardening

Gardening can still be enjoyed safely by taking a few practical precautions, especially when handling soil-based or organic materials that may produce dust or aerosols.

1. Wear a mask when handling dusty products

Using a mask when opening bags of potting mix, spreading mulch, or turning compost helps reduce the chance of breathing in fine particles. For these activities, a P2 or N95 mask is the most suitable option.

P2 masks are designed to filter at least 94% of airborne particles, including very fine dust that can’t always be seen. Gardening materials such as potting mix, compost and mulch can release tiny particles when disturbed, and these can be easily inhaled deep into the lungs. A properly fitted P2 mask provides a much higher level of filtration than basic surgical masks, helping reduce exposure to particles that may carry bacteria such as Legionella.

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2. Wear gloves and wash hands afterwards

Gloves help minimise contact with soil and organic matter, and thorough handwashing after gardening reduces the risk of transferring bacteria to the face or mouth.

3. Dampen materials before use

Lightly wetting potting mix, soil, compost or mulch before handling helps prevent dust from becoming airborne.

4. Work in well-ventilated areas

Open bags outdoors and avoid gardening in enclosed spaces like sheds or garages where dust can build up.

5. Avoid breathing in dust or mist

Keep materials away from your face when pouring or mixing, and avoid inhaling spray from hoses, sprinklers or water features, which is why wearing a mask is still something you should do at this point, and not just when you’re opening the bags of potting mix or compost.

6. Store gardening products correctly

Keep potting mix, compost and mulch in cool, dry areas and reseal bags after use to reduce bacterial growth.

When these products are stored in warm, damp or poorly ventilated spaces (such as sheds, garages or sealed containers exposed to heat), bacterial growth can increase. Over time, organic materials can begin to break down further, creating an environment where microorganisms, including Legionella, are more likely to thrive.

Storage do’s and don’ts for gardening products

✅ Do:

Store potting mix, compost and mulch in cool, dry and well-ventilated areas
Reseal bags tightly after each use to limit moisture and airflow
Keep products out of direct sunlight and away from heat sources
Use older bags first to avoid long storage times
Check stored products for strong odours, excess moisture or mould before use

❌ Don’t:

Store gardening products in hot sheds, garages or enclosed spaces that trap heat
Leave bags open or loosely folded, allowing moisture to build up
Store bags directly on damp floors or soil
Handle dry, dusty products indoors or in poorly ventilated areas
Ignore changes in texture or smell that may indicate bacterial growth

Conclusion: Garden safely with a little bit of awareness

Gardening is a healthy and enjoyable activity, and for most people it can be done safely with a little extra awareness. Understanding that Legionella bacteria can sometimes be present in common gardening products — particularly when materials are dry, dusty or poorly stored — helps explain why simple precautions matter.

By recognising higher-risk products, storing them correctly, and using protective measures such as gloves and a properly fitted P2 mask, you can significantly reduce the risk of exposure.

👉 Explore our range of PPE and safety essentials — including P2 masks, gloves and hygiene products — to help support safer gardening practices at home.

January 08 2026, by Tatianna Gerard Gardening Safely: Products Linked to Legionnaires’ Disease and How to Reduce Risk