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Advice on potting compost

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Risk of disease from potting compost very low

3 September 2010

There have been several stories in the press recently about potting composts being linked to Legionellosis. This is caused by a Legionella bacterium, L. longbeachae but the risk of catching Legionellosis from potting composts in the UK is thought to be extremely low. A more common form, Legionella pneumonophila, leading to legionnaires disease, is associated with standing water and requires temperatures of above 20°C to multiply. This may present a risk to gardeners from irrigation systems, water storage tanks and water left in hose pipes.

Elderly gardeners and those with a suppressed immune system are most vulnerable, but the RHS has the following advice for anyone concerned about the risk:

  • Wear gloves whenever handling soil, compost, fertiliser or pesticides.
  • Do not open bags of compost or potting media with your head right over it.
  • Avoid potting-up in confined spaces.
  • Moisten dry potting media before use. Also dampen down dry compost heaps before turning or use.
  • Consider wearing a dust mask when turning compost heaps and handling potting media or other dusty materials.
  • Avoiding storing potting media in greenhouses as these will heat up and may encourage Legionella.
  • Empty the water out of garden hoses after use and do not leave full hoses in the sun after use.
  • Avoid splashing water around when watering pots.
  • Keep water storage containers such as tanks and butts clean by emptying and scrubbing out once a year. Insulate them to reduce temperatures increasing in warm weather or paint them with a light colour to reflect the heat.
  • If the temperature of stored water for use in mist irrigation or sprinklers is above 20°C, do not use.
  • Always wash your hands after gardening and especially before eating.

More advice on minimising health risks in the garden

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