Cascara sagrada

Cascara sagrada (Kc) - Rhamnus purshiana

Page Index

Geographic Range & Ecological Amplitudes

Cascara sagrada is an erect tall shrub, less often a small-sized (<15 m tall), deciduous broad-leaved tree, at maturity with a narrow crown, slender stem, ascending branches, and smooth, dark grayish-brown, scaly bark. Cascara sagrada is not grown for timber production, but was grown for its bark, which contains a laxative of the same name. This use is reviving to some extent.
Geographic Range  Geographic element: Western North American/mainly Pacific and less Cordilleran Distribution in Western North America: central and south in the Pacific region; central and south in the Cordilleran region
Ecological Amplitudes 

Cascara sagrada
Climatic amplitude:
cool temperate - cool mesothermal

Orographic amplitude:
submontane - montane

Occurrence in biogeoclimatic zones:
(IDF), southern ICH, CDF, southern CWH

Edaphic Amplitude

Range of soil moisture regimes:
(slightly dry) - fresh - moist - very moist - wet

Range of soil nutrient regimes:
(poor) - medium - rich - very rich


Tolerances and Damaging Agents

Root System Characteristics Cascara sagrada has a shallow root system with many lateral branches.
tolerance to tolerance class comments
low light M moderately shade-tolerant in warm mesothermal climates
frost L does not tolerate open-area climate
heat H frequent on warm and dry sites
water deficit H frequent on dry and warm sites
water surplus H tolerates flooding and a strongly fluctuating water table
nutrient (mainly N) deficiency M absent in acid, very poor soils; infrequent in poor soils
Damaging Agents
damaging agent resistance class comments
snow L snowfall is very low in the CDF zone
wind M high winds will break boles and branches rather than uproot trees
  risk class  
fire L fire-resistant, except in the early developmental stage
insect L not a serious concern
fungi L not a serious concern (root and butt rots)
Associated tree species and successional role In British Columbia, cascara sagrada grows very scattered on disturbed sites in early and intermediate stages of secondary succession, usually in the understory of softwoods or hardwoods. On wet sites, it may be present in late seral stages.


Silvical Characteristics

characteristic interpretive class comments
reproduction capacity L very few individuals produce seed in forest understories
seed dissemination capacity M distributed by birds
potential for natural regeneration in the open H providing the presence of exposed mineral soil
response of advance regeneration to release na advance regeneration does not develop in the absence of adequate light and seedbeds
self-pruning capacity in dense stands na dense stands are very rare
crown spatial requirements M rarely a small tree
light conditions beneath closed-canopy, mature stands na closed-canopy stands are very rare
potential productivity na non-crop species
longevity L occasionally >50 years


Genetics and Notes

Notes The largest cascara sagrada are found on very moist or wet and nitrogen-rich, coastal sites. The tea or syrup obtained from boiling the bark of cascara sagrada has been proved to be an effective laxative. The plant was also used by First Nations people as a medicine for washing sores and swellings and treating heart strain, internal strain, and biliousness.