Frangula purshiana

Cascara buckthorn

Rhamnaceae

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.

Identification

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.

Threats

Fire effects: Cascara is usually top-killed by fire, but will sprout from the root crown following low-intensity fires.

Reproduction

Cascara usually reproduces by seed. It can also spread by layering and can sometimes be propagated by cuttings. Cascara will coppice after being stripped of bark and cut down.

Species Distribution

Citation

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.