UK gardens at risk from game changing plant disease

Wednesday 14 March 2018

  • Bacterium Xylella fastidiosa infects a huge variety of plants causing death in many instances
  • Popular garden plants such as cherry, lavender, hebe and rosemary considered high risk
  • Charity calls for sourcing of host plants from UK-grown stock to help mitigate threat

The quintessential UK garden, bursting with a wide variety of flowers, fruit and vegetables, could be lost to an unprecedented new disease in 2018, warns the Royal Horticultural Society (RHS).

Xylella fastidiosa – a bacterium which restricts water movement in plants resulting in eventual death – has already caused widespread devastation on the continent and threatens to arrive in the UK through the importation of infected plant material.

Unlike most pests and diseases which are plant-specific, Xylella affects more than 350 different plant species with garden favourites such as lavender, hebe, rosemary and flowering cherry at high risk because of their popularity, susceptibility to different strains of the disease and association with outbreaks on the continent.

The disease, which is spread by insects including leafhoppers and froghoppers is difficult to identify meaning it could advance unnoticed. Infected plants either show no symptoms or exhibit ones which may be confused with other common problems such as drought or frost damage. If found in the UK, all host plants within 100m would be destroyed and there would be restrictions on movement of plants within a 5km radius for five years - striking a death knell for surrounding nurseries and garden centres.

In light of the threat, the RHS is calling on gardeners and the industry to future proof gardens by purchasing host plants that are UK-sourced and grown – that is, propagated from seed in the UK or grown in the UK for a minimum of 12 months - maintaining varied plantings and reporting potential cases of Xylella to Defra.

To help mitigate the risk posed by Xylella, and other pest and diseases, the RHS is adopting six new principles that will guide its activity across gardens, shows and plant centres and hiring three new senior staff who will oversee plant health issues. Short term actions include:

  • Holding in isolation all imported semi-mature trees for at least 12 months prior to planting in RHS gardens and RHS shows where ever possible
  • Incorporating evaluation of plant health risk into judging criteria for gardens at RHS Shows
  • Wherever possible using UK grown and sourced plant material
  • Developing a central list of RHS-approved suppliers that meet specified plant health criteria

Gerard Clover, Head of Plant Health at the Royal Horticultural Society, said:Xylella is a game-changer for gardeners and the horticultural industry and it is vital that we understand its potential impact. Unusually, the disease threatens not just one host but hundreds of different types of garden plants and its impact has been felt dramatically in France, Spain and especially Italy where entire groves of ancient olive trees have been wiped out. The question for the UK is not ‘if’ but ‘when’ the UK will have its first outbreak of Xylella and the industry and public must be prepared for the far-reaching impact of it.”

For more information about Xylella and the RHS’s new plant health policies please visit



Notes to editors

 About the RHS: The Royal Horticultural Society was founded in 1804 by Sir Joseph Banks and John Wedgwood to inspire passion and excellence in the science, art and practice of horticulture. Our vision is to enrich everyone’s life through plants, and make the UK a greener, healthier, happier and more beautiful place. We believe everyone in every village, town and city should benefit from growing plants to enhance lives, build stronger, healthier, happier communities and create better places to live.

We held our first flower shows in 1820, were granted a Royal Charter in 1861 and acquired RHS Garden Wisley, our flagship garden, in 1903. From our first meetings in a small room off London’s Piccadilly, we have grown to become the world’s largest gardening charity. At our gardens and shows and through our scientific research, publications, libraries and our education and community programmes we inspire a passion for gardening and growing plants, promote the value of gardens, demonstrate how gardening is good for us and explain the vital roles that plants undertake.

The RHS is committed to bring the joy of gardening to millions more people, inspire the next generation of gardeners and invest in the future to safeguard a £10.4 billion industry employing more than 300,000 people. We are entirely funded by our members, visitors and supporters. RHS membership is for anyone with an interest in gardening. Support the RHS and help us secure a healthy future for gardening. For more information call: 020 3176 5820, or visit

RHS Registered Charity No. 222879/SC038262

For more information please contact Laura Scruby in the RHS press office: / 0207 821 3060

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About the RHS

The RHS believes that gardening improves the quality of life and that everyone should have access to great garden experiences. As a charity we help to bring gardening into people's lives and support gardeners of all levels and abilities; whether they are expert horticulturists or children who are planting seeds for the very first time.

RHS membership is for anyone with an interest in gardening. Support the RHS and secure a healthy future for gardening. For more information call: 0845 130 4646, or visit

RHS Registered Charity No. 222879/SC038262