The Pacific yew is the North American tree whose bark provided the chemotherapy drug paclitaxel.
Pacific yew, scientifically called Taxus brevifolia, is a slow-growing evergreen native to the Pacific Northwest of North America. It commonly grows as an understory tree in forests from northern California through British Columbia and into parts of Montana and Idaho.
In the 1960s, scientists screening plants for possible anticancer compounds found that extracts from Pacific yew bark contained paclitaxel, originally known as taxol. The compound interferes with cell division by stabilizing microtubules, structures that cells need to separate chromosomes.
Large-scale harvesting raised conservation concerns because removing bark can kill the tree, and Pacific yew grows slowly. Modern production uses cultivated yew plants and semi-synthetic methods. Paclitaxel is now used against several cancers, including ovarian, breast, and lung cancers.