Frangula purshiana - (DC.) Cooper
Cascara False Buckthorn
Other English Common Names: Cascara, Cascara Buckthorn
Other Common Names: Cascara buckthorn
Synonym(s): Rhamnus purshiana DC.
Taxonomic Status: Accepted
Related ITIS Name(s): Frangula purshiana (DC.) Cooper (TSN 506987)
French Common Names: Nerprun cascara
Unique Identifier: ELEMENT_GLOBAL.2.157732
Element Code: PDRHA0H060
Informal Taxonomy: Plants, Vascular - Flowering Plants - Buckthorn Family
Kingdom Phylum Class Order Family Genus
Plantae Anthophyta Dicotyledoneae Rhamnales Rhamnaceae Frangula
Check this box to expand all report sections:
Concept Reference
Concept Reference: Kartesz, J.T. 1994. A synonymized checklist of the vascular flora of the United States, Canada, and Greenland. 2nd edition. 2 vols. Timber Press, Portland, OR.
Concept Reference Code: B94KAR01HQUS
Name Used in Concept Reference: Frangula purshiana
Taxonomic Comments: Main synonym: Rhamnus purshiana. Common names: cascara (Little 1979), cascara sagrada, cascara false buckthorn (Kartesz 1999), cascara buckthorn (Elias 1980), bearberry, bearwood, bitterbark, chittam, chittem or chittim, coffeeberry, coffeetree, sacred bark, wahoo.

Usually known as Rhamnus purshiana DC., 1825 (type Clearwater River near Kamiah, Idaho). A discussion justifying use of the genus Frangula P. Miller (1754 or 1768) is in Kartesz and Gandhi (1994). Usually the group is considered as a part of Rhamnus L., sometimes being noted as the subgenus Frangula (P. Miller) Dipp. The genus Rhamnus is sometimes treated as masculine, but has been nomenclaturally conserved as feminine (Cronquist et al. 1997).

J.O. Sawyer Jr. in Hickman (1993) briefly characterizes but does not formally recognize Rhamnus purshiana var. annonifolia (Greene) Jepson, which as Rhamnus anonaefolia Greene, 1896 is treated as a synonym of the species (without discussion) by Abrams (1951) and Munz and Keck (1959).
Conservation Status

NatureServe Status

Global Status: G4G5
Global Status Last Reviewed: 30Jun2016
Global Status Last Changed: 24Mar2009
Ranking Methodology Used: Ranked by inspection
Rounded Global Status: G4 - Apparently Secure
Reasons: Although Frangula purshiana is widespread and sometimes common, and is robust, it apparently also is subjected to rather intensive exploitation in considerable portions of the species' range. Veninga and Zaricor (1976) stated that there remained an abundant supply of naturally growing trees which exceeded demand. However, some populations may have been extirpated (Yocom and Brown 1971), and many are likely to be used repeatedly, so that these populations probably no longer function naturally but instead are responding to human-induced (selection) pressures. The age structure of a utilized population, and habit and dynamics of individual trees or shrubs, may be significantly different than for wild populations, with evolutionary consequences.
Nation: United States
National Status: N4
Nation: Canada
National Status: N4N5 (02May2016)

U.S. & Canada State/Province Status
United States California (SNR), Idaho (SNR), Montana (S4), Oregon (SNR), Washington (SNR)
Canada British Columbia (S4S5)

Other Statuses

NatureServe Global Conservation Status Factors

Range Extent Comments: Southwestern Canada (British Columbia) and northwestern United States (Washington, Oregon and California, also Idaho and Montana). On the Pacific slope from southwestern British Columbia (including much of Vancouver Island) into northern California in outer Coast Ranges and the Sierra Nevada foothills (lower forest belt). Also disjunctly in the Rocky Mountains of southeastern British Columbia, far western Washington, northern (panhandle portion of) Idaho and northwestern Montana. The species' general distribution is mapped in Little (1971) and Krajina et al. (1982).

Number of Occurrences: 81 to >300
Number of Occurrences Comments: The species is fairly widespread and not infrequent in much of its range, and is sometimes common. It is considered common in southern British Columbia (south of 51?N), but rare farther north on the Queen Charlotte Islands (about 52?-54?N) (Douglas et al. 1991). Gilkey and Powell (1961) considered it common in the Pacific Northwest of Washington and Oregon. It is most common in the Puget Sound region of British Columbia and Washington, according to Collingwood and Brush (1965). The species was reported (Harshberger 1911) to be a common small understory tree on moist land in lower valleys of the dense forests to the east and southeast of Puget Sound.

In Pacific Northwest riparian forests, the species is never as abundant as Alnus rubra or Populus balsamifera subsp. trichocarpa (Kricher 1993, Habeck 1992). According to Kricher's discussion of these forests, the Populus (black cottonwood) lines river banks throughout the Pacific Northwest, and the Alnus (red alder) is also abundant along rivers and on disturbed sites from southern Alaska to southern California. Despite the wide distribution of Rhamnus, it is in the Pacific region that the genus is particularly important to animal wildlife; apparently, this is due to the relative abundance of certain species there, such as R. purshiana and three other [named] species (Martin et al. 1951).

The species is mostly distributed west of the Cascades (Habeck 1992). St. John (1963) stated that it was common along stream banks in southeastern Washington and adjacent Idaho. Harshberger (1911) reported that in the U.S. Rocky Mountains [e.g. in northern Idaho], it occurred with considerable frequency in the undergrowth of the (low-elevation) northern belt of Pinus ponderosa var. scopulorum, and that in northwestern Montana it is one of the more common shrubs in the Pinus monticola (mid-elevation) belt, which occurs on northern and eastern slopes and has its heaviest growth on level areas (including canyon bottoms) bordering the principal streams.

Population Size Comments: Scattered individual small trees occur in both old-growth and some second-growth Pacific Coast forests (Norse 1990).

Overall Threat Impact Comments: There is indirect evidence, obtained from reliable sources, of plant collecting from wild populations for the plant trade. Collingwood and Brush (1965) stated that the bark is collected extensively from trees in southern British Columbia, western Washington and Oregon, and northern California: "There is an annual harvest that comprises a forest industry of major importance to some rural regions." The bark is collected as strips peeled lengthwise.

Habeck (1992) reports the most effective collecting period to be mid-April until the end of August; the U.S. Forest Service (1963) stated that the peeling season usually runs from March through July. According to Sievers (1930), the collecting season opened about the end of May and closed before the rainy season set in. Veninga and Zaricor (1976) considered the collecting season to be in summer and continue until the rain ends in a region, as hot weather draws the sap from the bark into the inner tree. However, Clay-Poole (1999) reports that native North Americans considered it best to harvest the bark in late October and early November after the sap had descended down the trunk.

Collingwood and Brush (1965) stated that the demand is growing (even in competition with synthetic products), and that each year the bark gatherers must go farther back into the mountains. However, Hill (1998) reported that the chemical found in the bark can now be made synthetically, and for this reason a British Columbia law was removed that used to protect the species. In contrast, Tyler (1995) stated that some plant materials contain a large number of active principles and that purification may eliminate certain useful ones. He gave cascara (Frangula purshiana) as one of several examples where, "besides ... the isolation and purification of specific constituents is simply not necessary. It would be a waste of time and money to purify such herbal remedies ..."

Collingwood and Brush (1965) stated that in accessible areas, bark-peeling inroads have kept the average diameter down to 6 inches or less, and that such trees provide the major source of harvest. Veninga and Zaricor (1976) stated that the bark is collected properly by first cutting down the tree, so that a new tree will grow from the roots, but that if the tree is left standing and the bark stripped, it will die without resprouting. According to Collingwood and Brush (1965), a great deal of stump sprouting is precluded because the trees are not cut down after the bark has been peeled. Stumps sprout vigorously (coppice), producing 4 to 15 stems. "For this reason there is no dearth of wild bark at present."

However, Sievers (1930) reported that the tree will develop new bark if collectors in removing the bark allow enough to remain to prevent the tree from dying, and that this practice would prolong the natural supply of this valuable drug which was gradually being exhausted. Turner (1997) noted that Northwest Coast native peoples traditionally used the bark of many tree species for medicine, including cascara. Almost always, the bark pieces of the species utilized were cut in a narrow vertical strip from the sunrise side or river side of the tree. This practice was to allow the tree to continue to grow; the sunrise side was said to heal more quickly.

Michael McGuffin (in a meeting with Botany staff at TNC/ABI on Jan/10/2000) said that the American Herbal Products Association (AHPA) fairly recently surveyed its members regarding their trade in various species. He stated that their figures should be considered preliminary, and in general might include some double counting (if one company supplied another), resulting in over-reporting by as much as twice the actual usage. Thus a maximum total of 150,000 pounds of dried cascara bark per year may have been supplied in 1990, 1991 and 1992 by those AHPA members who responded, or the total for this species might be only half the above, 75,000 pounds per year (McGuffin email to TNC/ABI, Jan/27/2000). The AHPA has included this species in a more definitive planned tonnage survey for the 1999 season (AHPA letter to TNC, Jan/11/2000). He considered the cascara-sagrada trade an essentially steady rather than fluctuating market, and significantly in the market because the amount is relatively large, while noting that a few other species (particularly senna) were preferred as herbal laxatives. He was unaware of this species being cultivated (but will inquire), and thought the entire supply was probably from more or less wild sources (although likely with a well-organized/managed harvest because of company desire for stability in supply).

According to Habeck (1992), in a single [unstated] year 5 million pounds of dried cascara bark from the Pacific Northwest were processed by pharmaceutical companies. Prescott-Allen and Prescott-Allen (1986) reported (according to Norse 1990) that in Washington state, young men in interviews [year unstated] said that on a good day they could each bring in 280-300 pounds [presumably of fresh peeled bark strips -- Hill 1952, Veninga and Zaricor 1976]. The U.S. Forest Service (1963) stated that the bark's wet weight is about twice the dry weight.

The species was included in a list of the principal competing species on Pacific Northwest commercial forest land (Norse 1990), and the Vegetation Management Research Cooperative (VMRC) has selected this species to include in volume 3 (in preparation) of their autecology manuals on "problematic competitor plant species for forest vegetation managers" concerned with producing crop trees by reforestation in Washington, Oregon and northern California (VMRC 1999). Moore (1993) said that the species is especially common in heavily timbered forests.

Short-term Trend: Decline of 10-30%
Short-term Trend Comments: Apparently declining. Yocom and Brown (1971) stated that as a consequence of obtaining its medicinal bark, the species has been nearly extirpated in many places in the Humid Transition Zone of the Cascades (British Columbia into northern California).

The herbal industry organization United Plant Savers in 1999 put Cascara Sagrada (Rhamnus purshiana) on its "To Watch List" (United Plant Savers 1999). After the list was first published [about 1997], a commenter from Washington state had recommended including this species, stating that "This small tree, although plentiful at present, is continuously and unsustainably harvested (not coppiced) which kills the tree. This, along with its shrinking habitat leads me to believe Cascara will become scarce in a relatively short time." (United Plant Savers 1998)

Intrinsic Vulnerability Comments: The species was included in a list of the principal competing species on Pacific Northwest commercial forest land (Norse 1990), and the Vegetation Management Research Cooperative (VMRC) has selected this species to include in volume 3 (in preparation) of their autecology manuals on "problematic competitor plant species for forest vegetation managers" concerned with producing crop trees by reforestation in Washington, Oregon and northern California (VMRC 1999). Moore (1993) said that the species is especially common in heavily timbered forests.

Other NatureServe Conservation Status Information

Global Range: Southwestern Canada (British Columbia) and northwestern United States (Washington, Oregon and California, also Idaho and Montana). On the Pacific slope from southwestern British Columbia (including much of Vancouver Island) into northern California in outer Coast Ranges and the Sierra Nevada foothills (lower forest belt). Also disjunctly in the Rocky Mountains of southeastern British Columbia, far western Washington, northern (panhandle portion of) Idaho and northwestern Montana. The species' general distribution is mapped in Little (1971) and Krajina et al. (1982).

U.S. States and Canadian Provinces
Color legend for Distribution Map

U.S. & Canada State/Province Distribution
United States CA, ID, MT, OR, WA
Canada BC

Range Map
No map available.

U.S. Distribution by County Help
State County Name (FIPS Code)
CA Plumas (06063)
* Extirpated/possibly extirpated
U.S. Distribution by Watershed Help
Watershed Region Help Watershed Name (Watershed Code)
18 North Fork Feather (18020121)+, East Branch North Fork Feather (18020122)+, Middle Fork Feather (18020123)+
+ Natural heritage record(s) exist for this watershed
* Extirpated/possibly extirpated
Ecology & Life History
Basic Description: A small tree (or a shrub in drier habitats, such as the southern parts of its range; Collingwood and Brush 1965, Habeck 1992, Kricher 1993) with glossy parallel-veined leaves, small greenish-yellow flowers in stalked clusters, and small purplish-black berries. Growing to (3-) 9-35 (-45) feet high and 6-15 (-36) inches in diameter, with smooth dark brown to ashy gray thin bark developing thin scales (well illustrated in Collingwood and Brush 1965). The deciduous leaves are tufted at branch tips. The (usually) bisexual flowers occur in clusters of 8 to 25 (-50) that are arranged in long-stalked umbels. The black or dark purplish to bluish berries (drupes) are round (about 1/4 - 1/2 inch or 6-14 mm in diameter) and slightly fleshy, with usually 3 (or 2) smooth olive-green hard seeds. In California the species may flower in April-July, with the fruit ripening in July-September (Collingwood and Brush 1965, Vance et al., in press).
Ecology Comments: Frangula purshiana is essentially an understory species which is very shade tolerant, and slow growing (Kricher 1993, Norse 1990). Cooke and Pratt (1998) have data on the size and growth rate of this species in low-elevation wetlands in the Puget Sound Basin of Washington. Habeck (1992) has summarized some information on growth rates.

The species is considered a competitor plant species by forest vegetation managers concerned with producing crop trees. The competing "weed" [sic] species are those typical of sites being reforested in Washington, Oregon and northern California (Norse 1990, VMRC 1999).

The species is usually top-killed by fire, but will sprout from the root crown after low-intensity fire. In southern Oregon, natural low-intensity fires in its habitat may occur at intervals of 30-60 years, to 100-320 years; in some associations that include the species, high-intensity fires may occur every 60-150 years. Its primary ecological role may be that of a long-lived invader species (Habeck 1992).

The species is a prolific seeder. Birds eagerly eat the berries, and disperse the seeds (Collingwood and Brush 1965, St. John 1963, Schopmeyer 1974, Habeck 1992).

Habitat Comments: The species occurs in moist lowland areas to drier situations on lower mountain slopes.

It prefers rich well-drained soils where it gets moisture all summer, usually at low elevations (Hill 1998). It can occur in moist soils in bottomlands, lowlands, canyons, and on lower mountain slopes to 900 m/3000 ft (Elias 1980, Abrams 1951) or higher in California (below 2000 m - Hickman 1993). It can also be found along fence rows and roadsides (Elias 1980, Collingwood and Brush 1965).

It occurs in mesic to dry sites in British Columbia, in lowland steppe vegetation and montane zones (Douglas et al. 1991, Krajina et al. 1982). It is considered an indicator tree for the Pacific Northwest's temperate rain forest (old-growth mixed-conifer forest) and riparian forest (Kricher 1993, cf. Harshberger 1911). In the Western Cascades of Oregon on block basalt of lava flows near Santiam Pass, this species occurs as a shrub and is one of the major or representative species in an edaphic climax (Acer circinatum association). Inland in Oregon's Willamette Valley, the species is a major associate in a shrub-thicket community (now dominated by the exotic Rosa eglanteria) which occupies central portions of distinctive hummocks within bottomland prairie (Franklin and Dyrness 1973). In California it occurs in coniferous forests (e.g. Sequoia sempervirens flats, Sierra Pinus ponderosa belt) and also chaparral (Harshberger 1911, Hickman 1993). The species occurs along stream banks in southeastern Washington and Idaho (St. John 1963, Davis 1952), and in moist lowlands and on slopes in northwestern Montana (Booth and Wright 1966, Dorn 1984).

Economic Attributes
Economically Important Genus: Y
Commercial Importance: Indigenous crop, Minor cash crop
Production Method: Cultivated, Wild-harvested
Economic Comments: The bark is a source of a mildly irritant (i.e. stimulant) type of purgative (from anthraquinones) (Lewis and Elvin-Lewis 1977, Mowrey 1986). It was known to North American natives and introduced by the early Spanish. Use of the bark as a laxative was fully described by about 1805, and it has been well known since its first marketing by Parke-Davis in 1877; it was first officially listed in the U.S. Pharmacopoeia in 1890. Medicinally it is known as Cascara Sagrada or sometimes just as Cascara (Hill 1952, Collingwood and Brush 1965, Veninga and Zaricor 1976, Lewis and Elvin-Lewis 1977).

All parts of the plant have cathartic properties, but the bark especially; more than 50% of the active substance is stored in the woody parts (Collingwood and Brush 1965). Moore (1993) stated that bark of the limbs as well as the trunks is used. Other medicinal uses of the bark constituents are reported by Mowrey (1986). The sweetish (but rather insipid) berries are emetic, and also were utilized by Native Americans (St. John 1963). The fruit pulp has less of the cathartic than in some other Rhamnus species, and was used by early settlers as a coffee substitute (Milne and Milne 1975). In excess the fruits (and bark) are toxic (Hickman 1993, Kricher 1993).

Collingwood and Brush (1965) stated that the wood has no economic use other than for fuel, but that it could be used for turnery. Little (1978) noted that the species is used for fence posts. Habeck (1992) notes that the bark and the fruit have been used to make dyes.

Heiser (1993) stated that Rhamnus purshiana or cascara sagrada is the principal [medicinal] wild plant of northern North America in terms of the number of drug products produced (e.g. with powdered bark or liquid bark extract ) from the species. In 1977 the annual retail value of the bark in the United States was considered to be $75 million.

Sievers (1930), Hill (1952) and Moore (1993) are among those stating that the bark must be aged (naturally dried on racks) for at least 1 year before use (otherwise it is toxic). The bark is somewhat aromatic and extremely bitter in taste, tending to numb the taste buds (Habeck 1992, Kricher 1993). The longitudinal sections of peeled bark tend to roll up into large "quills" which are transported, and may be sun dried for example on sawmill platforms; the bark's inner surface is not exposed in order to retain the yellow color (Veninga and Zaricor 1976, Sievers 1930). The International Pharmacopoeia suggests that instead of aging, the bark may be dried by artificial heating to 100?C for 1 hour; Moore (1993) recommends 180?F for 24 hours, or in a dehydrator at 140?F for 12 hours. After drying, the quills are run through a "breaker", and the small transversely curved pieces bagged to retain the yellow color (Veninga and Zaricor 1976).

Prices for this species were found as follows:

U.S., internet, 1999: $9.24/half lb., $13.20/lb, $55.44/5 lb., $99/10 lb., $435.60/50 lb.

U.S., during World War II: $0.20/lb considered a good price (Hill 1998)

Management Summary Not yet assessed
Population/Occurrence Delineation
Minimum Criteria for an Occurrence: There are some localized disjunct populations relatively near to its main range (general maps are in Little 1971 and Elias 1980). In western rangeland, the species is considered a widespread but not abundant shrub found primarily in forested mountains; it often forms brushy stands (Habeck 1992). In Oregon the species occurs in woods especially west of the Cascades, but is widely distributed (Peck 1961).
Date: 19Jan2000
Author: MacBryde, B.
Population/Occurrence Viability
U.S. Invasive Species Impact Rank (I-Rank) Not yet assessed
NatureServe Conservation Status Factors Edition Date: 19Jan2000
NatureServe Conservation Status Factors Author: Bruce MacBryde

Botanical data developed by NatureServe and its network of natural heritage programs (see Local Programs), The North Carolina Botanical Garden, and other contributors and cooperators (see Sources).

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Citation for data on website including State Distribution, Watershed, and Reptile Range maps:
NatureServe. 2017. NatureServe Explorer: An online encyclopedia of life [web application]. Version 7.1. NatureServe, Arlington, Virginia. Available (Accessed:

Citation for Bird Range Maps of North America:
Ridgely, R.S., T.F. Allnutt, T. Brooks, D.K. McNicol, D.W. Mehlman, B.E. Young, and J.R. Zook. 2003. Digital Distribution Maps of the Birds of the Western Hemisphere, version 1.0. NatureServe, Arlington, Virginia, USA.

Acknowledgement Statement for Bird Range Maps of North America:
"Data provided by NatureServe in collaboration with Robert Ridgely, James Zook, The Nature Conservancy - Migratory Bird Program, Conservation International - CABS, World Wildlife Fund - US, and Environment Canada - WILDSPACE."

Citation for Mammal Range Maps of North America:
Patterson, B.D., G. Ceballos, W. Sechrest, M.F. Tognelli, T. Brooks, L. Luna, P. Ortega, I. Salazar, and B.E. Young. 2003. Digital Distribution Maps of the Mammals of the Western Hemisphere, version 1.0. NatureServe, Arlington, Virginia, USA.

Acknowledgement Statement for Mammal Range Maps of North America:
"Data provided by NatureServe in collaboration with Bruce Patterson, Wes Sechrest, Marcelo Tognelli, Gerardo Ceballos, The Nature Conservancy-Migratory Bird Program, Conservation International-CABS, World Wildlife Fund-US, and Environment Canada-WILDSPACE."

Citation for Amphibian Range Maps of the Western Hemisphere:
IUCN, Conservation International, and NatureServe. 2004. Global Amphibian Assessment. IUCN, Conservation International, and NatureServe, Washington, DC and Arlington, Virginia, USA.

Acknowledgement Statement for Amphibian Range Maps of the Western Hemisphere:
"Data developed as part of the Global Amphibian Assessment and provided by IUCN-World Conservation Union, Conservation International and NatureServe."

NOTE: Full metadata for the Bird Range Maps of North America is available at:

Full metadata for the Mammal Range Maps of North America is available at:

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