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Monday, November 17, 2014

Wood Science 101 (17) - Yew Better Know Your Wood

Back in the spring, I was doing some yard work that included winching out several old stumps of Japanese yew (Taxus cuspidata) that I had cut down seven years earlier. They were pretty bad boys and resisted the call of the winch; my friend's Jeep was sliding sidewards across the parking lot and the cable was singing as the root balls clung to their Mother Earth. But finally, stubbornly, each one came out with a groan and a crackle.

After the sounds of our ritual grunting died down, I examined the roots. Amazingly, they had come out nearly completely intact. The roots were thick, and still fleshy and pliable after all those years sitting dead in the dirt. But they were semi-rigid, and made quite interesting pieces. My friend suggested mounting a big bass in front of each, but I had another idea.

I had begun work on a large (440-gallon) aquarium project. These root balls, I thought, would make great structure in the tank for my pet fish to lounge around. And sure enough, the next day, the roots were dry and fully rigid...they looked great and were the perfect size to fill the large tank and still leave great swimming space for the fish.

Perfect for the tank..I think.

But the next morning, my very first thought on awakening was...Yew?! That's poisonous, isn't it?

Sure enough, a quick check confirmed that not only is yew poisonous, but it is one of the very most poisonous trees, with numerous recorded cases of livestock and human deaths due to ingestion of the branches and needles. In fact,
"The poisonous nature of the yew plant has been cited since the second century B.C. (Bryan-Brown, 1932). Julius Caesar (102–44 B.C.) documented an instance when Catuvolcus, the king of Eburones, poisoned himself with yew ‘juice’ (Fröhne and Pfänder, 1984). Celts committed ritual suicides by drinking extracts from yew foliage and used the sap to poison the tips of their arrows during the Gaelic Wars (Foster and Duke, 1990 and Hartzell, 1995). Some primitive cultures even used extracts as fish and animal poisons to aid in hunting (Watt and Breyer-Brandwijk, 1962 and Hartzell, 1995). During the 18th and 19th centuries, people in Europe and India used decoctions of yew leaf as an abortifacient and an emmenagogue (Bryan-Brown, 1932 and Watt and Breyer-Brandwijk, 1962)."
- Taxines: a review of the mechanism and toxicity of yew (Taxus spp.) alkaloids. Wilson, Sauer, and Hooser, Toxicon, 39:2-3, 2001.
I also discovered that yew poisoning is a real concern among wood turners, who love the look and feel of a well-turned yew bowl or pipe. But after a morning of on-line investigative work, I still hadn't convinced myself that there was any real danger to the fish. After all, the root wood was old and dead, right? And even though horses had been killed by ingesting only a few small needles, there wasn't any case I could find of fish being killed by yew. Sure, there was one landscaping site that recommended keeping yew away from outdoor ponds. But that was, I reasoned, to keep falling needles out of the water. What are the odds that there was enough poison in roots to kill fish? OK, maybe fresh roots...but not seven-year old dead roots, surely.

My first thought was to just stick the thing in there, and watch for any signs of distress. But the thought of twelve-inch barbs going belly-up within seconds (which is the speed that taxine, the poison in yew, can cause heart arrest in horses) gave me pause. And even though the taxine is not supposed to be water-soluble, I have several fish that like to chew on wood to remove the slime...might they trigger a Fish-bola extermination one day while I was away at work?

So, I got scientific, and brought some samples to work. Here, I recruited Brett Diehl, whom you've seen in a previous GoWood video on lignin, to run a mass spectrometer analysis for me to ascertain if there was indeed any detectable taxine. For comparison, I brought in some fresh yew parts and set Brett to work.

A few days later, the results were in. Not only was there taxine in the old root, but both components, taxine A and taxine B, were there in almost identical footprints as in the fresh root and needles. That meant that in fact, the poison was not water-soluble, since it remained essentially the same in the root material for years in the ground and not leached away. So, no danger of the fish dying within seconds of putting the root in the tank. But, several species of my fish are voracious eaters of plants and plant material, and the odds of one nipping off a root tip and heading on to Davy Jones' locker were just too high to risk.

So, I gave up on the yew root idea and bought some plastic plants. Oh, I and did manage to find some wood after all...the smaller pieces on the left-hand side of the tank are mopane (Colophospermum mopane), with a 12% MC specific gravity of 1.08, and the larger piece on the right-hand side is a great specimen of African leadwood (Combretum imberbe) which at 12% MC specific gravity of 1.22 is reported to be the sixth heaviest wood in the world. I can attest to that...the piece in the tank, which was given to me by a generous collector in New Jersey, weighed thirty pounds dry and was a heck of a challenge to get in the tank.

So, be careful on that next wood project, and if you or your loved ones are going to be chewing on it, be sure and do your homework. I was amazed to discover how many woods are poisonous. Quite enough for a future post on GoWood, I guess.


Peter Fahey said...

Wasn't Taxol, an anti-cancer drug, found and extracted from Yew ( until synthesized)? Funny how medicine and poison are so closely linked!

DaryleL said...

A very experienced industrial hygienist once made a point I have long remembered. There are no "toxic" substances--just "toxic amounts" of substances! That speaks to the above comment about medicine and poison.