Is our native yew tree poisonous?
Taxus brevifolia, Pacific or Western yew, is native here. The Sunset Western Garden Book (2001, p.628) says that Taxus fruit, seeds, and foliage are poisonous if ingested.
Plants of the Pacific Northwest Coast by Pojar and Mackinnon (Lone Pine, 2004) says that “Western yew seeds are poisonous and humans should avoid the fleshy ‘berries,’ although a wide variety of birds consume them and disperse the seeds. The foliage is poisonous to horses and cattle.”
The Plants for a Future database has more information at this link.