Forestry Commission logo
NEWS RELEASE No: 154331 MAY 2012

New facility pasteurises woodchip to halt spread of tree pests and disease at Westonbirt Arboretum

This news story is now over a year old and information may no longer be accurate or up-to-date. It might also contain obsolete links.
Please use our search link on the left to look for more recent information.
Andy Jane, Forestry Commission Recreation Ranger at Westonbirt Arboretum, looking at woodchip which has completed the pasteurisation process

The Forestry Commission’s National Arboretum at Westonbirt in Gloucestershire has a new facility for creating safe woodchip for use in and around the historic tree collection. 

Every year, arboretum maintenance produces hundreds of tonnes of woody material that is chipped and used for purposes such as mulching and path surfacing. The new facility pasteurises this material to kill any plant pests and diseases that might be present in the material.

The facility is the first of its kind in the country to pasteurise woodchip without adding green matter, which would cause the woodchip to become compost in the process.

The process relies heavily on nature. Assorted freshly chipped plant material is deposited into one of seven bays and covered. The covered pile generates heat as the chips decompose, similar to the way that a heap of green material generates heat as it becomes compost. Each bay measures 4.5m wide by 5.6m long and is filled to a depth of 1.5m.

To achieve pasteurisation, each pile of woodchip needs to reach a minimum of 45°C for five consecutive days or 60°C for three days.

Each pile is then turned and the process is repeated for a second and third time to ensure every piece of material is treated. Woodchip which is green at the start should turn to brown by the end of the process.

The process means the National Arboretum can use woodchip produced on site for laying paths, or as mulch around new trees and mature specimens without the threat of spreading plant pests and disease.

Following the discovery of the highly damaging Phytophthora ramorum pathogen in a specimen rhododendron in 2009, Defra served a plant health notice on Westonbirt Arboretum. The notice meant the use of woodchip produced from trees felled or maintained as part of routine management of the collection had to cease.

Mark Ballard, Curator at Westonbirt Arboretum, commented:

“Trees and plants face an increasing threat from new pests and diseases, and one of the ways they can spread is through the use of untreated woodchip.

“The decision was made to build this facility to reduce the risk of infection in Westonbirt’s tree collection and to save the extra costs of importing sterile woodchip.”

The new woodchip facility is located on Waste Drive in Silk Wood.

The project has been generously funded by the Friends of Westonbirt Arboretum, the charity which supports the Forestry Commission in a formal management partnership at the arboretum.


  1. Westonbirt, The National Arboretum is managed by the Forestry Commission and is renowned worldwide for its tree and shrub collection. Home to the National Japanese Maple Collection, the arboretum covers 243 hectares (600 acres) and contains 16,000 specimens. Visitor numbers are more than 350,000 a year, with a membership of more than 28,000. Westonbirt Arboretum was established in the 1850s by wealthy landowner Robert Holford, and later developed by his son George Holford. Unlike many arboreta, Westonbirt is laid out according to aesthetic appeal rather than scientific or geographic criteria. Visit
  2. The Forestry Commission is the government department responsible in England for protecting, expanding and promoting the sustainable management of woods and forests and increasing their value to society and the environment. Forestry makes a real contribution to sustainable development, providing social and environmental benefits arising from planting and managing attractive, as well as productive, woodlands.  Further information can be found at
  3. The Friends of Westonbirt Arboretum was formed in 1985. The charity’s objects are to support the National Arboretum in promoting public understanding of the crucial role of trees to the environment and society. It is funded by membership receipts from more than 28,000 members, other fundraising, and the use of the Great Oak Hall for events and activities. The Friends of Westonbirt Arboretum is a registered charity, No. 293190. More information at

MEDIA CONTACT: Katrina Podlewska, Communications Manager, Westonbirt, The National Arboretum, on 01666 881 207 or email: