May 21 2013 Latest news:
Martyn Davey, Head of Horticulture and Design, Easton College
Tuesday, May 8, 2012
Question: I have a large yew tree which is on my vegetable allotment. Can you tell me if the poisonous parts of the tree will affect the vegetables grown or the soil quality? I would like to know I am not slowly poisoning any recipients of the crops! (J Smith, via email)
Answer: The yew tree (Taxus baccata) is the oldest recorded tree. It is poisonous if eaten. Having said that, there is research at the moment looking into its cancer-fighting properties.
The foliage, bark, and seeds, but not the fleshy red aril, of most Taxus species are toxic due to the presence of taxine; this alkaloid, however, was not found in T. brevifolia. T. baccata (English yew) and T. cuspidata (Japanese yew), are best known and documented for toxicity.
Although livestock and humans have been poisoned by ingesting yew leaves and seeds, the fresh foliage of T. canadensis is browsed by deer and that of T. brevifolia by moose with no apparent ill effects.
With regard to your allotment I think having any tree over it would be a problem with the roots coming in under your crops and shading from the top of the tree.
However, if you are careful to remove all the leaves that fall on your crops before eating I don’t know of a reason why they would do you any harm. The leaves will rot down safely in the soil and help to provide organic matter.