Ageratina shastensis is a species of snakeroot which is endemic to Shasta County, California. It is known by the common names Mt. Shasta snakeroot and Shasta eupatorium. Ageratina shastensis is a woody perennial which bears unassuming fluffy white flowers about a centimeter wide. It is an uncommon plant which grows in the cracks of limestone cliffs of the Mount Shasta, part of the Cascade Range. Ageratina shastensis is a woody perennial which bears unassuming fluffy white flowers about a centimeter wide. It is an uncommon plant which grows in the cracks of limestone cliffs of the Mount Shasta, part of the Cascade Range.