How old is a tree? The Defynnog Yew

Can a tree really be over 5000 years old? According to some sources the yew tree in the church yard of St Cynnog’s in Defynnog on the edge of the Brecon Beacons might possibly be older than that. I’ve been wanting to visit Defynnog for some time now, and the weekend seemed like a good time to do so. It was a nice morning when I managed to bundle Aunty and Grandad into the car. However, it gradually got louder and darker as we headed north into the hills. By the time we’d got to Defynnog it was very heavily overcast and trying to rain. The weather seems to be recurring theme at the moment.

In the north side of the churchyard at St Cynnog’s Church is a very old yew tree. According to Fry in her book The God Tree, this impressive yew could have been planted up to 5000 years ago to mark a special site in the local landscape. This takes the tree back into the Neolithic period and the claim means that the tree was growing before the pyramids or Stonehenge was built. If true then the Defynnog Yew is not only the oldest tree in the U.K. but Europe. Spectacular! But could that be true? Probably not is the answer. The tree is huge, that can’t be denied, and seems to be split into two. The theory goes that this was originally one tree and through damage, maybe by lightening it was split and then continued to grow. At ground level the larger section has a measured girth 10.06m, or 36 feet in old money. Pretty big it has be said. The smaller section has a girth of 6.3m, or 28.8 feet. The distance between the two is a further 5m. So if these were in fact originally one tree then the overall girth of 24m before it was split and damaged. There is some serious maths behind all this, and I have to admit that I took this from a serious piece of work produced by the Ancient Yew Group (Ancient-Yew.org).

For such a large and potentially ancient tree, the earliest documented mention of the yew is 1975 when Joseph Russell Bailey noted there were 3 yew trees in the churchyard ‘all walled around’. The walls are just about discernible now, but have been replaced by old gravestone now leaning at all angles. Some serious work has gone into trying to age the yew, but also in attempting to determine if the two trees are different or the same individual. In 2011 samples from both trees were tested at the Roslin Forestry Research Institute which confirmed that both tress contained the same DNA. This seems to suggest that they have both grown from the same stock. But if they are not one tree that has been damaged in the past what else could explain this fact.

It is not unknown for yew trees to spread out from the main tree by layering. If a branch from the main tree comes to rest on the ground it can start to develop roots of it’s own. Overtime the connection between the ‘parent tree’ and the layered branch can be broken and rot away completely leaving both trees growing separately. This to me seem to be the most likely explanation for both trees growing closely together and sharing the same DNA, rather than both having been the same tree and then separated by an environmental incident.

How do you age an ancient tree? This is extremely difficult. The most direct route would be to count the tree rings. But to do this you would either have to cut it down, which is not an option to a growing tree. A core sample could be taken allowing a dendrocrinologist to count the rings. Easy then! Well no quite. As yews grow to a ripe old age they hollow out from the centre. This allows the tree to become more flexible as the girth of the tree expands outwards, which reduces the risk of being damaged or blown over in high winds. So this isn’t and option then. There are mathematical algorithms that take into found girth measurements ect. But without direct evidence it is difficult to validate. This is made more difficult by the fact that yews grow at different rates at different stages in their age. Growth can also be affected by the climate, which over 3000 years can vary a great deal. At present the best evidence we have, official and unofficial, implies that the largest girthed Defynnog yew might have begun growing during the Iron Age: so it may quite possibly be over 2,000 years old, but is very unlikely to be as much as 3,000.

So the Defynnog yew may not be 5000 years old, but 3000 years is pretty impressive to me. This tree has been growing through the Bronze Age, the Iron Age, was here when the Romans invaded the British Isles and then left again, through the Dark Ages right up to todays technological age. Now that is a mind bending thought. A single living organism has been growing quietly all this time, making is mark on the landscape. I like that idea.

References

Hindson, T. (2014) Addressing the claim that the Defynnog Yews in Powys might be 5000 years old. Ancient Yew Group. Ancient-Yew.org/userfiles/file/Defynnog%20v4f5.pdf.