The leaves are lanceolate, flat, dark green, 1–3 cm long and 2–3 mm broad, arranged spirally on the stem, but with the leaf bases twisted to align the leaves in two flattish rows either side of the stem except on erect leading shoots where the spiral arrangement is more obvious.

The seed cones are highly modified, each cone containing a single seed 4–8 mm long partly surrounded by a modified scale which develops into a soft, bright red berry-like structure called an aril, 8–12 mm long and wide and open at the end.

[4] The entire yew bush, except the aril (the red flesh of the berry covering the seed), is toxic due to a group of chemicals called taxine alkaloids.

[9] The estimated (i.e. not by any means a fact) lethal dose (LDmin) of Taxus baccata leaves is 3.0-6.5 mg/kg body weight for humans[16] There is currently no known antidotes for yew poisoning, but drugs such as atropine have been used to treat the symptoms.

[20] The following book made it clear that it is very difficult to measure taxine alkaloids and that this is a major reason as to why different studies show different results.

[21] Minimum lethal dose, oral LDmin for many different animals were tested: Several studies[22] have found taxine LD50 values under 20 mg/kg in mice and rats.