When country people fell victim to ‘the plague’, the area of the churchyard in which they were buried would have greenery from the yew trees cut down and scattered over the ground, in the belief that its acidity and its toxins would counteract those of the rotting corpse. Conversely, fronds of yew greenery would be cut down and laid upon the pathway to the church door at Easter time, simulating the way in which the ground before Christ’s feet was strewn with palm fronds when he rode an ass into Jerusalem. On a more mundane note, farmers whose land was adjacent to church yards and cemeteries would be sure to keep their hedges and fences in good order for fear of their livestock straying into the holy ground and grazing on the yews.

04 Berries thumb

So what of the toxic qualities of yew? Just about the whole tree is toxic, indeed, the only part which can safely be eaten, is the red, fleshy aril which develops as a seed case to each seed, but don’t let that lull you into a false sense of security if you decide to eat them, because the seed inside it is poisonous! So too, is the timber, especially when inhaled or ingested as dust, and the early peasants who scattered yew leaves over graves were correct in their belief of its toxicity, although I don’t know if the effects that they sought would take place. Even the pollen released by the male yew tree, is a cytotoxic substance! The major toxin within the tree is Taxine, which can prove fatal when ingested in sufficient quantities, although horses are especially vulnerable and need only to ingest a small amount of leaves before the taxine takes effect. This has been known to man for many millennia, indeed, during the Gallic wars in which the mighty Roman Empire subjugated much of the former Celtic regions of Europe, Julius Caesar recorded in his writings, that Catuvolcus, chief of the Eburones chose to commit suicide by eating yew leaves, rather than submit to Rome. Similarly, taxines were the chosen vehicle of suicide amongst many a soldier amongst the Cantabrian and Astures armies in 22BC and 25BC respectively.

Interestingly, the flower of the male plant bears a yellowish-white globe-like structure, and it is this element of the yew which bears the most toxin.  The Ogren Plant Allergy Scale (OPALS), lists plant allergens on a scale of 1, through to 10, and declares that this is a ‘10’ on their scale, whereas the female flower can be as low as ‘1’.

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In 1021, Avicenna (a Persian philosopher) made the first recorded use of yew extracts as a medicine, naming his herbal drug ‘Zarnab’ and using it to treat cardiac disorders. He knew what he was doing, for in the late 1960s, western medicine suddenly realised the importance of this drug as a calcium channel blocker, and has since used it extensively. Furthermore, in 1967, the researchers Wall and Wani developed a process to extract paclitaxel (Taxol), an anti-cancer treatment, from the leaves of the Pacific Yew (Taxus Brevifolia), but this process was fraught with difficulties. Extraction rates were poor and destruction of Pacific Yew became an issue, with Al Gore stepping in to add weight to the anti-Taxol debate. However, it was then discovered that the European yew, Taxus Baccata, yielded very significantly higher amounts of the drug, and that the process of extraction was considerably simpler. Nowadays, yew is still involved in the production of Taxol, but the process now uses small amounts of it as a catalyst for a semi-synthetic process. Meanwhile, in the Central Himilayas, extracts of yew are currently used as treatment for breast and ovarian cancer.

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The tree itself is an evergreen softwood and it is dioecious; the male and female flowers grow on different trees. However, with the yew’s ability to generate new growth from its roots, it occasionally happens that a new stem of a female tree, grows as a male off-spring, and vice versa. Indeed, the tabloid press recently reported the ‘…sensation’ of Scotland’s oldest yew tree, the Fortingall Yew, undergoing a ‘…sex change’; a classic piece of sensationalist, tabloid reporting of an event which in fact, was quite normal in the natural world, and simply an example of monoecious sub-growth. Typically, mature yew trees grow to about 22 yds (20 metres) in height and can reach a girth of about 7 to 8 yds (6 to 7 meters) before the heartwood decays and subsequent, regenerative growth develops, in which case the tree can be as much as 40 ft (13 meters) in girth. The foliage is of dark green, needle-like leaves, generally between 0.5 and 1.5 inches (1.2 and 3.5cm) in length, arranged in pairs along a stem. The seed-cones are unusual, in that they are single-seeded and develop with an aril, which in turn develops into a red, fleshy, open-topped outer casing, whilst the male reproductive element is a yellowish-white, globe-like flower which can be mistaken by casual observers, for a seed.

07 Pot with silver staples thumb

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Saturday the 16th. Thanks for visiting Woodturners Unlimited.