Frangula purshiana

Cascara buckthorn


The Basics

Taxonomy: Kingdom - Plantae (plants). Subkingdom - Tracheobionta (vascular plants). Superdivision - Spermatophyta (seed plants). Division - Magnoliophyta (flowering plants). Class - Magnoliopsida (dicotyledons). Subclass - Rosidae. Order - Rhamnales. Family - Rhamnaceae (buckthorn). Genus - Frangula Mill. Species - Frangula purshiana (DC.) J.G. Cooper

Ecology: Cascara generally grows on lower mountain slopes. It may also inhabit moist canyons on the east slope of the Cascades. In Oregon, cascara is generally a moist-site indicator. Cascara is very tolerant of shade. Being shade tolerant, it is often found in the understory of second-growth forests. Therefore, its primary role seems to be that of a long-lived invader species.

In the WFDP: Cascara is very rare in the WFDP, with only one stem above 1cm at DBH that is tagged.


Cascara is a deciduous, erect, tall shrub or small tree. It can attain a height up to 10 m at maturity, but becomes smaller in size and bushier along its southern distribution. West of the Cascades, it develops a single trunk 20-30 cm thick, 6-10.7 m tall. It has greenish-yellow flower petals approximately 3-4 mm long. Cascara has a purplish-black drupe about 7.5 mm in diameter, containing several seeds. The leaves are oblong, 7.5-12.5 cm long, and have 10 to 12 pairs of prominent parallel veins arising directly opposite each other on the midrib.


Fire effects: Frangula purshiana has the ability to sprout from the root crown from a low intensity fire. After a fire the top is usually killed and if the fire gets too hot the species will not be able to grow back. Off site seeds can be carried onto to eh site after 2 years as a secondary colonizer. For managing the fire for Frangula purshiana fires often occur every 30 to 60 years. The understories are often free from any heavy fuel which can lead to high intensity fire.


Casara is usually reproduced by seed. It can be spread by layering and sometimes be propagated by cutting. 20 pounds of seeds per 100 pounds of fruit per plant. Birds are the distributors of the seeds from consuming the fruit. Frangula purshiana will coppice after being stripped of bark and cut down.

Species Distribution


USDA Plants Database
USDA, NRCS. 2016. The PLANTS Database. National Plant Data Team, Greensboro, NC 27401-4901 USA.

USFS Plant Database
Habeck, R. J. 1992. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory.

The Jepson Herbarium
The Jepson Manual: Vascular Plants of California. B.G. Baldwin, D.H. Goldman, D.J. Keil, R. Patterson, T.J. Rosatti, and D.H. Wilken [editors]. 2012. 2nd edition, thoroughly revised and expanded. University of California Press, Berkeley, CA. $131.95, hardcover; 1600 pages. ISBN-13: 978-0520253124.

Burke Museum of Natural History and Culture
Burke Museum. 2016 [Online]. University of Washington.
Photo credit: G.D. Carr 2008

USGS Plant Species Range Maps
Critchfield, W.B., and Little, E.L., Jr., 1966, Geographic distribution of the pines of the world: U.S. Department of Agriculture Miscellaneous Publication 991, p. 1-97.
Little, E.L., Jr., 1971-1978, Atlas of United States trees, volume 1,3,13,17, conifers and important hardwoods: U.S. Department of Agriculture Miscellaneous Publications.