Most gardeners are aware that Tetanus is a bacterial infection that can enter the body through cuts or abrasions that have been in contact with soil. It may surprise everyone to find out that there are other ‘nasties’ that may be lurking in the garden, specifically in bags of compost, compost heaps, garden hoses and even hot tubs.


Legionella is a bacteria, which is transmitted via water vapour. The source is usually associated with air conditioning systems, hot tubs and spas, so it was quite a surprise when the discovery was made that it can live, in the right conditions, in potting soil. When gardeners are turning over compost, it is possible to breathe in fine water droplets and that’s where the danger lies. It normally thrives when the water temperature is between 20°C to 45°C.

Legionella longbeachae was first identified in Long Beach, California in 1980, but since then a number of countries have reported cases of illness involving this particular bacterium that has been linked to potting compost. This species of legionella, if inhaled, can cause Pontiac Fever, which is a flu-like illness, sometimes resulting in severe lung infections.

Legionella pneumonophila can also be found in potting soil and compost, if inhaled it could lead to Legionnaires’ disease, a type of pneumonia (first discovered in the USA in 1976). That said, it is extremely rare to contract the above-mentioned diseases through gardening, but it doesn’t hurt to be aware of the conditions that make the organisms thrive. Elderly gardeners and those with a suppressed immune system are most vulnerable.

Hose pipes

Gardeners should also be aware that Legionella can be found in hose pipes. The combination of warm weather and sitting (stagnant) water, creates the perfect environment for legionella bacteria to grow.

WRAS and Water UK have produced a booklet called Looking after water in your home.

Water Butts

Did you know that up to 95% of UK garden water butts could be contaminated with legionella bacteria? In recent studies, scientists working on behalf of Public Health England at the Porton Down facility, sampled water from 113 water butts to determine whether legionella was present. A startling 107 water butts tested positive, with just six testing negative.

As legionella can grow in water temperatures above 20oC, water butts can pose a significant risk in the warmer months.

Tips to keep you safe from legionella

  • When opening a bag of compost or potting soil, make sure your head isn’t directly over it.
  • It’s not a good idea to store compost or potting soil in greenhouses as these will heat up and may encourage Legionella.
  • Consider wearing a dust mask when turning compost heaps.
  • Empty the water out of garden hoses after use.
  • Do not leave full hoses in the sun after use.
  • Avoid using water from garden water butts when the temperature inside the butt is likely to rise above 20oC.
  • Only use water from water butts via a watering can, do not use the water via a hosepipe or sprinkler.
  • Clean water butts every year.
  • Consider insulating water butts to keep water temperatures below 20oC.


Rats may be attracted to a compost heap, especially if vegetable peelings or food waste have been added. Their urine can contain Leptospirosis, which causes flu-like symptoms, such as a headache, chills and muscle pain.

Although rare, in some cases the infection is more severe and can cause life-threatening problems, including organ failure and internal bleeding. In its most severe form, Leptospirosis is also known as Weil's disease. It can enter the body via cuts and abrasions.

Gardeners should also be aware that ponds and water features could be contaminated with rat urine.

Minimise risk of Leptospirosis (Weil's disease) by

  • Wearing gloves whenever handling soil, compost or fertiliser.
  • Wearing waterproof gloves, clothing and boots when clearing out ponds.
  • Rat-proof compost bins – this can be done by adding wire mesh.

Legionnaires' disease

Find out more about the causes of Legionnaires' disease and how you can avoid Legionella in your water systems.

Find out more

Leptospirosis / Weil's disease

Find out more about the causes of Weil's disease and how to stay safe from Leptospira bacterium.

Find out more

Download safety booklet

WRAS and Water UK have produced a booklet called Looking after water in your home.

Find out more