Free Growth of Oak

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The Forestry Commission took ownership of Crumblands Plantation in Monmouthshire in 1930 and planted the site with oak at 13,400 trees per hectare the following year.  In 1951 an experiment was established on the subject of free growth of oak, the objective of which was to produce a high proportion of veneer quality timber to a diameter of 60 cm on a rotation of less than 100 years.  Over the intervening decades, notwithstanding some setbacks, the experiment has survived and provides a tremendous focus for discussions on growing oak in Britain.

In November 2016 the late Chairman of Woodland Heritage, Peter Goodwin, led a party of experts and oak growers to sites in France (as well as the UK) for further investigation of claims that fine oak can be achieved in 100 years.  They asked:

How does the mass of data accumulated by French managers over 30 years and encapsulated in Jean Lemaire’s book,  ‘Oak: fine timber in 100 years’, compare with the research at Crumblands?

This was answered during a meeting organised by Woodland
Heritage and Forest Research on 19 April 2018 in Devauden, southeast Wales.

100 people attended this sell-out event, which included a field visit to the Forest Research long-term experiment in to the free growth silviculture to Oak at Crumblands Plantation.

Free growth silviculture aims to maximise the diameter increment of 60-70 trees per hectare by giving their crowns conditions of ‘free growth’ by removing competing trees. It is best described as having three parts:

  • Selecting – 60-70 trees per hectare are selected early on in the life of the stand that have good form and vigour, usually when top height is between 10-12 m.
  • Thinning – the selected trees are then thinned every 3-5 years to remove all competing trees in a halo around the crown of the tree. 
  • Pruning – this is carried out as required on the free growth trees to ensure that epicormic branches do not survive and become a problem later in the life of the trees.

Interest in maximum rate of diameter growth of Oak had been stimulated by observations of very fast diameter growth of Oak trees that had been isolated by very heavy fellings during the Second World War. This had led Forestry Commission scientists to design the concept of ‘free growth’ to test whether similarly fast diameter growth of Oak could be achieved in productive woodlands.

The results are quite amazing and show just how quickly Oak can grow in Britain if treated in the right way. They are also a triumph of long-term research carried out by Forest Research.

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