Yew: the graveyard plant that is now saving lives

In the mid-1990s I spent a month doing research at Aberdeen University. During the week I sat transcribing letters in the library. On the weekends, I explored the coast and countryside in a borrowed van. One warm(ish) day in June, I visited Crathes Castle near Banchory. The castle dates from the 16th century, but what I mostly remember from my visit was the gardens, particularly the tall yew hedges that walled in the different spaces. Yew grows to a great age, and these hedges, well over 9 feet tall, date from the beginning of the 18th century.

Yew hedges at Crathes Castle, near Banchory. Photographer Darren Foreman, from Wikimedia Commons

The day I was there, a gardener was trimming the hedges. Balanced on a ladder, a good 8 to 9 feet above me, he was carefully saving all the clippings in a plastic garbage bag. The work looked precarious, and I asked him why he was taking so much trouble to save the trimmings. He told me they were parcelled up and sent to the Pasteur Institute in Paris, where scientists were working on a cure for cancer.

Yew has long been grown as a hedge, or as specimen trees, for it is not just decorative but useful. English longbows were made of yew, and at one time all villages were expected to grow yew trees so that wood was available to make bows in time of war.

But yew is also poisonous. People probably first realised yew was a poison because animals grazing near the trees could die – especially horses, which have a particularly low tolerance, but also other domestic animals, including dogs. Even sleeping in the shade of a yew was considered dangerous. The solution was to grow yew trees in churchyards (or castle gardens) where the plants couldn’t endanger straying livestock.

Yew trees have long been associated with graveyards; Gray’s Elegy Written in a Country Churchyard mentions the ‘yew-tree’s shade’, and Tennyson, in In Memoriam, refers to

Old Yew, which graspest at the stones
That name the under-lying dead,
Thy fibres net the dreamless head,
Thy roots are wrapt about the bones.

This link with churches and religious sites generally is very old, predating Christianity. Both Celtic and Norse religion mentions the yew. Its poison made it powerful.

According to the Renaissance scholar Paracelsus,

All substances are poisons; there is none which is not a poison. The right dose differentiates a poison and a remedy.

This is certainly the case with yew. The Islamic physician Avicenna knew it as a poison, but also recommended it as a cardiac drug, and mentioned it in his Canon of Medicine (1021).

It is also true in chemotherapy. The aim of chemo is to kill fast-growing cells with poison. These include cancer cells but not only cancer cells, for other fast-growing cells – hair, fingernails, blood and mucus – are also poisoned. The body takes a terrible battering, and it is only the dose that distinguishes the drug from the poison.

In the 1960s, scientists at the National Cancer Institute in America began to experiment with yew as a potential chemotherapy drug. Using bark from the Pacific Yew (Taxus brevifolia) they isolated a cytotoxic substance which they called Taxol. They began experimenting on mice in the 1970s, and began clinical trials of humans in 1982.

Taxol looked promising as a cancer drug – but it took a great deal of bark to extract it, and stripping the bark kills the trees. By the 1980s, the National Cancer Institute estimated that to produce enough Taxol to treat all melanomas and ovarian cancers in the US, 360,000 trees a year would need to be harvested.

It is hard to argue against the production of an effective cancer drug – but for a while it looked as if the Pacific yew would be driven to extinction. Yew is long-lived, but grows slowly, and the forests of the Pacific Northwest looked in danger. (This would not be the first time that a medical breakthrough leads to over-harvesting. Quinine is made from the bark of a Peruvian tree, cinchona, which was nearly lost to over-harvesting until plantations were introduced in the 19^th century.)

At the same time in Europe, work was going on using the European Yew (Taxus baccata). The clippings from Crathes Castle’s yew hedges, along with many other ancient and modern yew trees, went into producing another taxol-like drug, Doxetaxol, which is made from twigs and leaves, not bark, so doesn’t kill the tree. Meanwhile in America, Taxol is increasingly made from cultivated yew rather than wild forests – though also from another wild yew, the Canadian yew (Taxus canadiensis). We are not quite out of the woods yet.

Those people who have read my blog in the past may know that I was diagnosed with breast cancer last year. I mentioned my operation here, and warned that I might not be able to update the blog regularly while I had cancer treatment. I’ve finally finished that treatment now, which included 3 cycles of Doxetaxol.

I can vouch for the fact that yew is a poison. At times while on Doxetaxol, everything ached, even the fillings in my teeth! But if the treatment has worked – and my chances are good – I owe a lot to that gardener at Crathes Castle, carefully collecting twigs and leaves while teetering on a ladder 9 feet above the ground. I owe a lot to the scientists too, of course, but it is easy to forget the many anonymous volunteers who have helped too, because ‘finding a cure for cancer’ is something we all hope for.

Anyway, I’m back at last – and I hope to be able to blog regularly once more. Thanks to all those who have sent me good wishes during the last few months.

Update: A friend who grew up in Britain sent me the following response –

‘It made me think of all the children’s stories I have read over the years of the Yew tree people. People didn’t build houses next to Yew trees because the sprites of the tees could turn into real people and interfere in their lives. They were not generally for the good. But if a baby cried they would rock the cradle. If they thought a baby was neglected they would spirit it away. Marion’s blog fits in with the folk tales very well. Poisonous – so keep away. But when the need arises they pop out and do humans good deeds. Folk tales send out messages.’

Which made me think – even more creepily – that the current investigation in the UK into pedophilia, following the disclosures about the late jimmy Savile, is called ‘Operation Yewtree’. Does anyone know why?

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