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Hentland churchyard yew tree

Hentland church in 1916: a yew tree is partly obscuring the tower.

Photograph by Alfred Watkins courtesy of Hereford City Library

 
 

In summer 2005 the Vicar of Hentland measures her yew tree
 

Analysis of the Hentland Churchyard Yew by David Lovelace

 

Planting date

Woolhope Club

LOWV

Date

1605

1868

2005

Interval years

 

263

137

Girth, feet

 

12

14

Girth, inches

 

144

168

Girth, mm

 

3657.6

4267.2

Radius, mm (divide by 2 x Pi)

 

582.1

679.1

Difference 1868 to 2005

 

 

97.0

Mean ring width 1868 to 2005

 

 

1.41

Age by linear extrapolation 2005 to 1868

1524

 

481

Mean ring width from 1605 to 2005

 

 

1.70

Mean ring width from 1605 to 1868

 

2.21

 

Taking the Woolhope Club measurement and their planting date (1615 + their assumption of the tree being 10 years old when transplanted) gives a mean ring width of 2.2mm. Our measurement comparing with that of 1868 gives 1.4 mm, which can be interpreted as the growth rate slowing with age due to: senescence, shading by adjacent trees and/or pollarding/pruning. These figures are consistent with the few published records:

A yew tree recently felled to protect the masonry at West Horsley, Surrey allowed a detailed analysis of its rings showing a mean ring width of 2.8 mm for the 1st 100 years and 0.9 mm for the next 210 years (see www.tree-ring.co.uk).

There is a large variation of ring width with age reported from one of the few publications on the subject (Tabbush and White, Quarterly Journal of Forestry, July 1996 pp 197-206, 'Estimation of Tree Age in Ancient Yew Woodland at Kingley Vale') namely 3.5mm for early growth down to 0.051 for older trees, a factor of 70.  

Given this uncertainty, the simple extrapolation from our single measurement which extended the age from 400 to 480 years and equivalent to a 20% error is actually quite reasonable.

Tabbush and White published a formula relating the final ring width to age which obviously requires a small coring – something which we might (with permission) carry out? However this assumes a known variation of ring width with age and an accurate measurement of final ring width

I am sceptical of this method for at least one reason namely that the corrugated cross section of a yew butt means that a single measurement is inherently unreliable. Rings can even disappear a some points around a Yew tree’s circumference which would, according their formula, mean an infinite age. No wonder stories of 4000+ year old yew trees proliferate

 
 

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This project was part-financed by the European Union (EAGGF) and DEFRA through the Herefordshire Rivers LEADER+ Programme.