Yew tree age estimates
Small stands of yew and many of the largest trees may be found in the churchyards and cemeteries of England and Wales, and the parish churches of Britain provide a unique assemblage of the largest yews known in Europe. (Taxus baccata L.) is generally acknowledged as the British tree capable of longest life, Bevan-Jones reviews the evidence concluding: "evidence from many quarters emphasises the reality that these trees frequently exceed a thousand years growth".
Distribution and girth of some yew trees in the south of the U.K.
(click map to enlarge)
The estimation of the age of yews has been a contentious subject for centuries, not least because those specimens over 4.57m girth are normally hollow. Tree age estimation in the U.K. has remained largely based on girth measurement comparisons, but exceptionally large trees have been aged by different methods and estimates can widely vary accordingly.
An estimate of the age of churchyard yew trees from girth
* Age Estimate = based on formula published by Tabbush & White (1996) and is based on research on churchyard yews
The only precise way to determine the age of a living tree is to measure tree rings usually in a section or increment core that intersect the pith of the tree. The use of a narrow (5.14mm) diameter increment corer to sample a live tree offers the same astonishing impact of absolute tree-ring dates as has been achieved with the dating of historic timber-framed buildings in this country. While the girth of our very largest trees (and hence the trees of greatest interest) may make it impossible to reach their piths with increment borer, increment sampling still offers the most accurate empiric refinement to the estimation of a tree's age. In some instances we can also use a technique which combines the mean growth rate information from a site to further refine the age estimation of trees sampled.
Yew has been show to have considerable dendrochronological potential, however tree-ring analysis has yet to be applied to a tree over 5.20m in girth. There are a number of particular problems in the dendrochronological study of yew, for example, slow growth in this species may lead to extremely narrow rings, and in some cases, locally absent or "missing" rings which can cause potential ring counting errors during measurement. Another problem is the common irregular and lobate growth pattern of the trunk and the consequent risk of missing rings from core samples. However, recent research has demonstrated that yew may be successfully core sampled from lobe sections of growth and dendrochronologically analysed. For the cost of dating a Churchyard yew tree by tree-ring analysis click: costs.
A yew tree approximately 3 meters in girth and so estimated to be 300 years old was recently in danger of being fell, at Hunton Bridge, Herts. Advice from the Ancient Tree Forum lead to the contact of the District Council's Tree Officer, who arrived within the hour to apply an emergency Tree Preservation Order. It was later discovered that the tree was also an important roost site for bats. All bats are specially protected species. For this and other recent news articles on trees see the Ancient Tree Forum's Latest ATF news.
- Moir, A K 2004 Dendrochronological analysis of a Churchyard yew tree from West Horsley, Surrey, England, Tree-Ring Services, Dendrochronological Report, WHCX/xx/04 (Out Soon)
- Moir, A K 2003 Dendrochronological analysis of two yew trees and one oak tree from St. John the Baptist Churchyard, Capel, Surrey, England, Tree-Ring Services, Dendrochronological Report, CACY/27/03.
- Moir, A K 2003 Dendrochronological analysis of trees from St. James the Great Church, Thorley, Bishop's Stortford, Hertfordshire, England, Tree-Ring Services, Dendrochronological Report, THCY/04/03.
- Moir, A K, 1999 The dendrochronological potential of modern yew (Taxus baccata) with special reference to yew from Hampton Court Palace, UK, New Phytologist 144, 479-488.
- Tabbush, P, White, J E J, 1996 Estimation of tree age in ancient yew woodland at Kingley Vale. Quaterly Journal of Forestry 90: 197-206.