Frangula purshiana, Cascara buckthorn
Habeck, R. J. 1992. Frangula purshiana, Cascara buckthorn. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: https://research.fs.usda.gov/feis/species-reviews/frapur
| Abbreviation | Common Name | Scientific Name | Classification | Status |
|---|---|---|---|---|
| Plants | ||||
| FRAPUR | Cascara buckthorn | Frangula purshiana | Life Form: Plants/Shrub, Plants/Tree Kingdom: Plantae Class: Dicot Order: Rhamnales Family: Rhamnaceae Genus: Rhamnus | Fed. Protected: No Nativity: Native Invasiveness: Noninvasive |
Taxonomy
The scientific name of Cascara buckthorn is Frangula purshiana (DC.) A. Gray. Recognized subspecies are [28]:
- Frangula purshiana (DC.) A. Gray subsp. annonifolia (Greene) Sawyer & S.W. Edwards, Cascara annona-leaved buckthorn
- Frangula purshiana (DC.) A. Gray subsp. purshiana, Cascara buckthorn
- Frangula purshiana (DC.) A. Gray subsp. ultramafica Sawyer & S.W. Edwards, Cascara serpentine buckthorn
Synonyms
- Rhamnus purshiana DC [12]
Other Common Names
bearberry, cascara, cascara sagrada, chittam bark, coffee-tree
General Distribution
Cascara buckthorn generally occurs from British Columbia down through northern California. It is mostly distributed west of the Cascades but can also be found east to northern Idaho and northwestern Montana [1,12].
States and Provinces
- United States: CA ID MT OR WA
- Canada: BC
Site Characteristics
Cascara buckthorn generally grows on lower mountain slopes [1]. It may also inhabit moist canyons on the east slope of the Cascades. In Oregon, Cascara buckthorn is generally a moist-site indicator [2]. It is commonly found with red alder (Alnus rubra) on moist bottomlands but is rarely abundant [1].
Site characteristics from southern Oregon Cascade Mountain Province where Cascara buckthorn is found as a forest nominal component are as follows [2]:
| Site characteristic | Range of means |
|---|---|
| Elevation (ft) | 2,447 - 4,232 |
| Slope (%) | 13.0 - 53.0 |
| Soil depth (in) | 34.6 - 46.7 |
| Rooting depth (in) | 39.3 - 50.0 |
| Mean annual temp. (F) | 43.9 - 48.8 |
| Max. month temp. (F) | 77.5 - 84.7 |
| Mean annual precip. (in) | 36.7 - 67.5 |
| Dry season precip. (in) | 6.0 - 8.8 |
| Litter (%) | 70.7 - 98.7 |
| Moss (%) | 2.3 - 45.2 |
| Bareground (%) | 0.2 - 4.0 |
| Gravel (%) | 0.3 - 3.8 |
| Rock (%) | 0.4 - 6.1 |
| Bedrock (%) | 0.0 - 3.8 |
Plant Communities
Cascara buckthorn, Willamette Valley, OR.
Cascara buckthorn is predominantly a shrub component on forested sites in the Pacific Northwest. No information was found listing Cascara buckthorn as an understory dominant or site indicator. Cascara buckthorn was listed, however, as a member of a prairie community occupying a floodplain in the Willamette Valley, Oregon. It was also listed as a representative species in a vine maple (Acer circinatum) plant association on a lava flow near Santiam Pass, Oregon [9]. In southern Oregon, Cascara buckthorn was found as a component in many plant associations in the white fir (Abies concolor), Douglas-fir (Pseudotsuga menziesii), and western hemlock (Tsuga heterophylla) series [2].
Plant associations in southern Oregon where Cascara buckthorn is listed as a component are as follows [2]:
| Plant associations | Constancy (%) | Minimum % cover | Maximum % cover | Range | Mean | SD |
|---|---|---|---|---|---|---|
| Western Hemlock (TSHE) Series | 2.0 | 1.0 | 2.0 | 1.0 | 1.2 | 0.4 |
| TSHE/GASH/LIBO | 5.0 | — | — | — | 1.0 | 0 |
| TSHE/PSME/GASH | 8.0 | — | — | — | 1.0 | 0 |
| TSHE/GASH-CHUM | 25.0 | — | — | — | 1.5 | 0.7 |
| TSHE/ACCI/RUNI | 11.0 | — | — | — | 1.0 | 0 |
| White Fir (ABCO) Series | 2.0 | 1.0 | 8.0 | 7.0 | 2.8 | 3.5 |
| ABCO/ACGL/BENE | 10.0 | — | — | — | 1.0 | 0 |
| ABCO/COCOC-AMAL | 16.0 | — | — | — | 8.0 | 0 |
| ABCO-CADE3/BENE | 4.0 | — | — | — | 1.0 | 0 |
| ABCO-PSME/BEPI | 3.0 | — | — | — | 1.0 | 0 |
| Douglas-fir (PSME) Series | 3.0 | 3.0 | 3.0 | 0 | 3.0 | 0 |
| PSME/RHDI/CYGR | 33.0 | — | — | — | 3.0 | 0 |
Scientific names for species used above are as follows:
- ABCO Abies concolor
- ACCI Acer circinatum
- ACGL Acer glabrum
- AMAL Amelanchier alnifolia
- BENE Berberis nervosa
- BEPI Berberis piperiana
- CADE3 Calocedrus decurrens
- CHUM Chimaphila umbellate
- COROC Corylus cornuta californica
- CYGR Cynoglossum grande
- GASH Gaultheria shallon
- LIBO Linnaea borealis
- PSME Pseudotsuga menziesii
- RHDI Rhus diversiloba
- RUNI Rubus nivalis
- TSHE Tsuga heterophylla
Botanical Description
Cascara buckthorn flowers, Mount Hood National Forest, OR.
Cascara buckthorn is a deciduous, erect, tall shrub or small tree. It can attain a height up to 33 feet (10 m) at maturity, but becomes smaller in size and bushier along its southern distribution [29]. West of the Cascades, it develops a single trunk 8 to 12 inches (20-30 cm) thick, 20 to 35 feet (6-10.7 m) tall. It has greenish-yellow flower petals approximately 0.12 to 0.16 inch (3-4 mm) long [23]. Cascara buckthorn has a purplish-black drupe about 0.3 inch (7.5 mm) in diameter, containing several seeds [5,20]. Cascara buckthorn is very tolerant of shade [1]. The leaves are oblong, 3 to 5 inches (7.5-12.5 cm) long, and have 10 to 12 pairs of prominent parallel veins arising directly opposite each other on the midrib. The leaf buds have no scales [12,27].
Raunkiaer Life Form (Raunkiaer 1934)
- Phanerophyte
Seasonal Development
Major phenological activities of Cascara buckthorn in northern Idaho are as follows [22]:
| Year | Bud swell | Leafing out | Stem growth | Blooming | Fruit growth | Leaf color change | Leaf fall |
|---|---|---|---|---|---|---|---|
| 1971 | NA-4/27 | 5/4-5/19 | 5/11-7/21 | 5/26-6/9 | 6/18-NA | 9/30 | NA |
| 1972 | 4/19-5/6 | 5/6-6/2 | 5/19-7/12 | 5/22-6/13 | 6/20-NA | 10/9 | NA |
| 1973 | NA-4/23 | 5/2-6/4 | 5/2-7/4 | 5/28-6/12 | 6/19-NA | 10/2 | NA |
Regeneration Processes
Cascara buckthorn usually reproduces by seed. It can also spread by layering and can sometimes be propagated by cuttings. Cascara buckthorn will coppice after being stripped of bark and cut down [11,29].
Seeds: Cascara buckthorn generally produces 20 pounds (18 kg) of seeds per 100 pounds (90 kg) of fruit. Cleaned seeds range from 5,000 to 19,000 seeds per pound (4,500-17,100 kg), with an average of 12,300. Recommended sowing depth is 1 inch, with seedbed shading [13]. Birds are the predominant distributors of Cascara buckthorn seeds [1].
Morphological characteristics of Cascara buckthorn fruit from Rainbow Creek Research Natural Area, southeast Washington are as follows [24]:
| Morphological Characteristic | Mean |
|---|---|
| Fruit diameter (mm) | 11.6 |
| Fruit mass (mg) | 796.8 |
| Pulp dry mass (mg) | 126.1 |
| Number of seeds per fruit | 3.0 |
| Fresh seed mass per fruit (mg) | 165.2 |
| Fresh pulp mass (mg) | 3.8 |
Successional Status
Cascara buckthorn has not been cited as a dominant species in any forest habitat type described for the Pacific Northwest. Being shade tolerant, it is often found in the understory of second-growth forests [1]. Therefore, its primary role seems to be that of a long-lived invader species.
Immediate Fire Effects
Cascara buckthorn is usually top-killed by fire [29].
Preburn and postburn measurements of Cascara buckthorn in central Idaho were as follows [17]:
| Timing | Average live crown diameter (ft) | Average live crown height (ft) | Average crown below 7 ft (%) | Average dead crown (%) | No. Basal Sprouts | Average sprout height (ft) |
|---|---|---|---|---|---|---|
| Preburn | 4.0 | 8.0 | 95.0 | 95.0 | 1.0 | 1.5 |
| Postburn | 3.0 | 4.5 | 100.0 | 100.0 | 18.0 | 3.0 |
- Preburn measurements were taken in March, 1965. Postburn measurements were taken in August, 1965.
- Postburn measurements were taken on the part of the plant which existed before treatment.
- All Cascara buckthorn's aboveground parts were completely killed by the fire.
Postfire Regeneration Strategy (Stickney 1989)
- survivor species; on-site surviving root crown or caudex
- secondary colonizer; off-site seed carried to site after year 2
Fire Adaptations
Cascara buckthorn sprouts from the root crown following low-intensity fires [11,29].
Plant Response to Fire
Change in Cascara buckthorn measurements after prescribed burns in northern Idaho were as follows [16]:
| Year | Average preburn crown height (cm) | Average preburn crown diameter (cm) | Average no. basal sprouts per plant | Average sprout height (cm) | Max. crown height 2 years after burn (cm) | Max. crown diameter 2 years after burn (cm) |
|---|---|---|---|---|---|---|
| 1965 | 244 | 91 | 18 | 91 | — | — |
| 1966 | — | — | — | — | 183 | 137 |
| 1970 | — | — | 12 | 76 | — | — |
| 1971 | — | — | — | — | 137 | 107 |
| 1975 | — | — | 7 | 76 | — | — |
| 1976 | — | — | — | — | 122 | 107 |
Fire Regimes
For fire regime information, search FEIS for this species by entering the species name or acronym on the home page and selecting “Fire Regime” as the publication type.
Fire Management Considerations
Fire intervals on southern Oregon sites where Cascara buckthorn occurs range from 30 to 60 years, to longer intervals of 100 to 320 years. These understories are generally free from heavy fuels, giving rise to low-intensity fires. In some plant associations that include Cascara buckthorn, however, high-intensity, stand-replacing fires occur approximately every 60 to 150 years [2].
Federal Status
None
Other Status
No entry.
Importance to Wildlife and Livestock
Cascara buckthorn is a widespread but not abundant shrub found primarily in forested mountains [27]. It has been listed as a browse species for mule deer in Oregon [7,29] and for elk in northern Idaho [26]. Cascara buckthorn was found to be a winter browse species for mule deer in northwestern Oregon. Sixty-eight percent of available Cascara buckthorn shrubs were browsed during the winter. In summer, however, Cascara buckthorn was less desirable; only 27 percent of available Cascara buckthorn shrubs were browsed [6]. Other mammals that browse Cascara buckthorn include the black bear, gray fox, raccoon, and ringtail [1,29]. Cascara buckthorn drupes are eaten by five species of birds including the ruffed grouse and band-tailed pigeon. Cascara buckthorn is of no value as forage for livestock [30]. How the purgative characteristics of Cascara buckthorn bark and drupes affect wildlife are not known [29].
Palatability and Nutritional Value
Although utilized by wildlife, Cascara buckthorn is not very palatable. Cascara buckthorn is browsed very lightly by sheep and to some extent by mule deer, but for all practical purposes its forage value is negligible [27]. Palatability of Cascara buckthorn leaves to elk on the Selway Game Preserve, Idaho was poor [30].
The relish and degree of use shown by wildlife species for Cascara buckthorn in British Columbia are as follows [4]:
| Species | Palatability |
|---|---|
| Bighorn sheep | Poor |
| Elk | Fair |
| Moose | Poor |
| Mule deer | Poor |
| White-tailed deer | Poor |
| Caribou | Poor |
| Coast deer | Good |
The nutritive value of Cascara buckthorn is poorly understood. Cascara buckthorn was found to be nitrogen-rich in one southern British Columbia study [14].
Cover Value
Cascara buckthorn often forms brushy stands capable of providing abundant thermal and hiding cover [2]. The shrubby form may prove a more valuable cover species than the treelike northern form [29].
Value for Rehabilitation or Restoration of Disturbed Sites
No entry.
Other Uses
The greatest known value of Cascara buckthorn is its purgative properties. In a single year, five million pounds of dried Cascara buckthorn bark from the Pacific Northwest was processed by pharmaceutical companies in the manufacture of laxatives [1,23].
The Kootenai and Flathead tribes of western Montana used Cascara buckthorn as a laxative, consuming it in the form of a tea brewed from the bark. These Indians believed that it would be a purgative when the bark was stripped downward. If stripped upward, the drug would act as an emetic. Cascara buckthorn bark contains anthraquinare derivatives, tannin, resins, starch, glucose, and other compounds [11]. When the bark is chewed, it tastes extremely bitter, and may temporarily numb the taste buds [1].
The flesh of some animals which have consumed the drupes is said to retain some of the purgative properties. The juice pressed from the berries is used to prepare a 'syrup of Cascara buckthorn'. The bark and dried berries have been used as a source of yellow- and saffron-colored dyes. The berry juice, when combined with alum, produces a green dye once used by artists [21].
Apparently, if Cascara buckthorn is handled for a long time, the laxative effects can even be transferred through the skin [1]. For maximum effectiveness, bark collection is recommended from mid-April to the end of August, and bark should be stored as long as possible before being used [11].
Other Management Considerations
Disease: Cascara buckthorn has been found to be susceptible to laboratory exposures of crown rusts [29].
Herbicides: Garlon 4 and Tordon 101 applied during early foliar development top-killed 95 percent of Cascara buckthorn 3 years after treatment [19].
Table A1— Forest and range ecosystems, Bureau of Land Management (BLM) physiographic regions, Kuchler plant associations, Society for American Foresters (SAF) forest cover types, and Society for Rangeland Management (SRM) rangeland cover types in which this species occurs.
Forest and Range Ecosystems (Garrison et al. 1977)
- FRES20 Douglas-fir
- FRES21 Ponderosa pine
- FRES23 Fir - spruce
- FRES24 Hemlock - Sitka spruce
- FRES25 Larch
- FRES27 Redwood
- FRES28 Western hardwoods
- FRES34 Chaparral - mountain shrub
BLM Physiographic Regions (Bernard and Brown 1977)
- 1 Northern Pacific Border
- 2 Cascade Mountains
- 4 Sierra Mountains
- 5 Columbia Plateau
- 8 Northern Rocky Mountains
Kuchler Plant Associations (Kuchler 1964)
- K001 Spruce - cedar - hemlock forest
- K002 Cedar - hemlock - Douglas-fir forest
- K003 Silver fir - Douglas-fir forest
- K005 Mixed conifer forest
- K010 Ponderosa shrub forest
- K011 Western ponderosa forest
- K012 Douglas-fir forest
- K029 California mixed evergreen forest
SAF Cover Types (Eyre 1980)
- 205 Mountain hemlock
- 206 Engelmann spruce - subalpine fir
- 210 Interior Douglas-fir
- 211 White fir
- 212 Western larch
- 221 Red alder
- 224 Western hemlock
- 225 Western hemlock - Sitka spruce
- 226 Coastal true fir - hemlock
- 227 Western redcedar - western hemlock
- 228 Western hemlock
- 229 Pacific Douglas-fir
- 230 Douglas-fir - western hemlock
- 233 Oregon white oak
- 234 Douglas-fir - tanoak - Pacific madrone
- 237 Interior ponderosa pine
SRM Rangeland Cover Types (Shiflet 1994)
- No entry.
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