Question: What is the name of one of the native species of buckthorn that is also a powerful plant-based laxative?

Related documents: [0]  [DOC] Rhamnus purshiana (cascara buckthorn, cascara, bearberry, and in the Chinook Jargon, chittem and chitticum; syn. "Frangula purshiana", "Rhamnus purshianus") is a species of buckthorn native to western North America from southern British Columbia south to central California, and eastward to northwestern Montana. [END] 
[1]  [DOC] Coffee cherry tea is a herbal tea made from the dried skins of dried berries (or "cherries") of the coffee plant. It is also known as "cascara", from the Spanish cáscara, meaning "husk". It is different from cascara sagrada tea, a powerful plant-based laxative. [END]  
Answer: Rhamnus purshiana
Rhamnus purshiana