Taxus baccata is the botanical name of yew. It is a small- to medium-sized deciduous tree, growing 10–20 metres (33–66 ft) (exceptionally up to 28 m/92 ft) tall, with a trunk up to 2 metres (6 ft 7 in) (exceptionally 4 m/13 ft) diameter. The bark is thin, scaly brown, coming off in small flakes aligned with the stem. The leaves are lanceolate, flat, dark green, 1–4 centimetres (0.39–1.6 in) long and 2–3 millimetres (0.079–0.12 in) broad, arranged spirally on the stem, but with the leaf bases twisted to align the leaves in two flat rows either side of the stem, except on erect leading shoots where the spiral arrangement is more obvious. The leaves are highly poisonous.
The seed cones are highly modified, each cone containing a single seed 4–7 millimetres (0.16–0.28 in) long partly surrounded by a modified scale which develops into a soft, bright red berry-like structure called an aril, 8–15 millimetres (0.31–0.59 in) long and wide and open at the end.
It is relatively slow growing, but can be very long-lived, with the maximum recorded trunk diameter of 4 metres probably only being reached in about 2,000 years. The potential age of yews is impossible to determine accurately and is subject to much dispute.