Wednesday, January 21, 2015

Yew

Very long day at the office today so this will be a shit post. However, it will be a post.
Poor pic of yes, another evergreen! This time it's one of the three native conifers: yew, or Taxus baccata
It is very shade tolerant and very poisonous. There is a product derived from yew that was developed as a chemotherapy drug which is now found impregnated on metal stents that are used to re-open arteries in the heart that have been narrowed by atherosclerosis. The drug slows the growth of cells colonising the stent to reduce the likelihood of early re-stenosis. 
I did read somewhere that the flesh of the attractive red fruits (called arils) can be eaten, so long as you don't ingest the seed, but I think I'd have to be pretty desperate to try this out. One vernacular term for them is snotty-gogs.
It is a fascinating species and I will write more tomorrow. Suffice to say that the oldest surviving wooden artefact is made from yew and estimated to be about 250,000 years old! The tree with the largest girth in Britain is a yew estimated to be between 2000-3000 years old (although some say 'only' 1500 years old). Amazing. 

Okay, so here's the rest, added on 23rd January:
The artefact is a spear head found at Clacton in Essex! That is extraordinarily old. Pre-dating several glaciations. Knowing that the last glaciation ice sheets retreated from Britain around 12,000 years ago puts that in perspective.
Yew-related gossip includes the one about Pontius Pilate having played under the Fortingall Yew (the one mentioned above as being incredibly old - Mabey quotes 2000 - 9000 years!) as a child when his father was reputedly stationed in Scotland as a legionary.
But the genuine fascination with yew in this country (and to some extent northern France) is its association with churchyards. No one really knows the answer to this. There are around 500 churchyards with yews at least as old as the church itself. The distribution of yews in churchyards correlates with the distribution of yews in the wild. 
It was said that Edward I passed a law preventing rectors felling trees in the graveyard as a means of protecting yews for the purpose of harvesting for longbows. However longbows are fashioned from the trunk not the boughs so you'd have to fell the tree to use them. Furthermore most of the yew used for longbows (and it was far from the best wood for the purpose) was imported from Spain and Italy. 
Another theory is that churches used yew branches as a substitute for palms on Palm Sunday, which certainly is known to have occurred. Another, that churches were often built on pagan sites which in turn were positioned near yew trees which were venerated for reasons forgotten by the Druids. It is interesting to note that until the Middle Ages people generally didn't plant trees, suggesting that churches must have already had yew trees in their grounds when they were built.
Ageing a yew tree is basically impossible. After about 400 years they start becoming hollow and lose any heartwood that could be radioisotope dated. They also go into prolonged periods of dormancy when they more or less stop putting on girth. One tree increased its girth from 30 feet to 30 feet and 9 inches in 250 years!
The name 'yew' is derived from one of the oldest of the Celtic tree names: iw
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