by Ian Brand

Wharfedale Naturalists Society

WHEN I was a young medical student, I soon realised every person I met had an interesting story to tell. It was often the older members of society who had the best tales.

Likewise with plants, they also have fascinating stories, none more so than one of my favourite trees, Yew (Taxus baccata), winter never being a better time to take a look at conifers. Here are just a few of its stories.

Firstly, that Latin name ‘Taxus’, which comes from the Greek word ‘Taxon’ meaning bow. Yew was the best wood for manufacturing the renowned English longbow.

Taxus is also where we get the word ‘toxic’ from, with most of the tree extremely poisonous. Luckily for Thrushes and other birds that eat the berries, it does not include its sweet red flesh or aril.

Trying to estimate the age of these most long-lived of trees is difficult. No one is sure at what age they start to hollow, or why some years they grow so little they produce no annual growth rings.

Finally, Yew has also given us one of the most commonly used chemotherapy drugs of recent years, Paclitaxel (Taxol). The National Cancer Institute in America, in the late1950s & 60s looked at thousands of plants for potential sources of anti-cancer drugs. They found only two leads, one of which was the Pacific Yew (T. brevifolia). In 1964 bark extracts were found to be toxic to living cells. It took a further seven years to isolate Taxol and it was 1979 before it was discovered to work in a completely new way against cancer. A eureka moment! Only problem, Taxol was only found in the bark, and in low concentrations. It took the bark from six trees to treat one patient and harvesting the bark killed the tree!

The search went out to find a Yew species where the chemical was in the leaves, not just the bark. They did not need to look too far; our European Yew (T. baccata) contained a similar chemical molecule in its leaves, which with a little modification could produce Taxol. So the call went out to country houses, like Levens Hall in Cumbria with its famous topiary, to save its Yew clippings to produce Taxol. It is still produced today from Yew, but semi-synthetically in plant tissue culture.

Taxol may not be the golden bullet, but has certainly become a game changer for both ovarian and breast cancer.

www.wharfedale-nats.org.uk