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Why are Taxus yew seeds toxic?

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The massive Grizzly Giant sequoia tree stands with a wide, reddish-brown trunk and a hollowed base, surrounded by other tall trees in Mariposa Grove, Yosemite National Park. — Conifer A giant sequoia (*Sequoiadendron giganteum*) estimated to be between 1,900 and 2,400 years old, Grizzly Giant is the oldest tree in the Mariposa Grove, Yosemite National Park, California.

Taxus yew seeds are toxic because they contain poisonous alkaloids, specifically a bitter substance known as taxine.123

While the fleshy, cup-shaped aril that envelops the seed is not poisonous, the seed itself and the foliage of the yew tree contain these toxic compounds, which can be fatal to humans and various animals if ingested. It is important to note that while some birds, such as thrushes, can safely consume the aril and pass the intact seed in their droppings, the seeds remain highly dangerous to those who might chew or digest them.12

Ethically, it is vital to recognize the potential danger these plants pose to children and livestock, and one should always exercise caution and prevent the ingestion of any part of the yew plant, excluding the aril, to ensure safety.12