Monkshood (Aconitum columbianum)
Aliases: Columbian Monkshood, Western Monkshood
Family: Buttercup (Ranunculaceae)
Monkshood is common to mid-elevation meadows and stream banks in Yosemite, particularly along Glacier Point Road. It's tall and lanky, capable of surpassing six feet. It's also notably toxic; Plants for a Future claims that mere skin contact can make people feel a bit off.
Blooms: June - August
Lifespan: Perennial
Origins: Native (see distribution maps for California and US/Canada)
Aconitum columbianum etymology: Aconitum is the ancient Greek name for the genus. Columbianum indicates a plant found in western North America. It's a tribute to Christopher Columbus, who, to his credit, did get within a few thousand miles of western North America on his voyages.
This Photo: Near a stream on the Westfall Meadow trail, mid July
Other Resources: CalFlora · CalPhotos · USDA · eFloras.org