Buckthorn – Rhamnus purshiana Share this:Click to share on Pinterest (Opens in new window)Click to share on Facebook (Opens in new window)Click to share on Twitter (Opens in new window) Designed with love! Our Grower's Choice Subscription freshly picked and delivered to your door every month. Shop Now Common Name: Buckthorn, Cascara Sagrada Botanical Name: Rhamnus purshiana, RAM-nus per-shi-AH-na Decorative Life: 2-3 weeks. Availability: Spring, Summer Storage Specifics: 34-38F. Tidbits: Rhamnus was a city along the coast of Ancient Greece. Cascara sagrada means “sacred bark” in Spanish. The bark is the source of a strong laxative.