Common Name: Cascara Sagrada

General Information

Frangula purshiana is an erect, deciduous to semi-evergreen shrub or a small tree that can grow from 1 - 12 metres tall. The boles of larger specimens can be 20 - 30cm in diameter. Plants are tallest in the north of its range, becoming more shrubby towards the south[, ].
A popular domestic medicine, the plant is harvested from the wild and also cultivated for its bark[]. The plant is also harvested from the wild for a variety of other local uses, and can be grown as a hedge.
Frangula purshiana is fairly frequent across its expansive geographic range and there are expected to be a large number of individuals. There is concern that the population is in decline due to the targeting of the species for its bark, which is in demand as a laxative medicine. Currently, this decline is estimated to fall below 30% but this use should be monitored and steps taken to ensure the sustainability of harvest. The plant is classified as 'Least Concern' in the IUCN Red List of Threatened Species(2018)[].

Known Hazards

Species in this genus contain hydroxyanthracene derivatives which have a stimulant laxative effect upon the body, and many species are used traditionally as laxatives. In small doses, and for short periods, these can be safe and effective, but used over long periods they can weaken the body's natural ability to defecate and can have a range of long-lasting negative effects upon the body, including anaemia, malabsorption, haematuria and weight loss. Large single doses can cause severe purging.
Apparently, if Casara buckthorn is handled for a long time, the laxative effects can even be transferred through the skin[].

Botanical References

, ,

Range

Western N. America - southern British Columbia, Washington, Oregon, Idaho, Montana, northern California.

Habitat

Rich bottom lands and sides of canyons, usually in coniferous forests[, ]. Coniferous forests, forest edges, deciduous woodlands, stream banks, coastal sage scrub, non-serpentine substrates; at elevations up to 2,000 metres[].

Properties

Conservation Status	Least Concern
Edibility Rating
Medicinal Rating
Other Uses Rating
Habit	Evergreen Tree
Height	10.00 m
Pollinators	Insects
Cultivation Status	Wild

Cultivation Details

Frangula purshiana is a moderately cold-hardy plant, able to tolerate temperatures down to around -15°c when fully dormant[], 238.
Succeeds in any reasonably good soil in sun or partial shade[, ]. Plants are very tolerant of shade[].
This species is cultivated as a medicinal plant in N. America[, , ] and is also collected from the wild[].
In a single year, more than two million kilos of dried Casara buckthorn bark from the Pacific Northwest of America was processed by pharmaceutical companies in the manufacture of laxatives[]
The plant is becoming rare in the wild because of over-collection[].
Plants respond well to coppicing[].
The flowers are produced in small clusters on shoots of the current year's growth[].
Closely related to Frangula alnus[].
The species in this genus are notably resistant to honey fungus[].

Edible Uses

Fruit - raw or cooked[, , , ]. A thin, rather juicy flesh[]. It is sometimes eaten[]. There is some debate as to whether the fruit is edible or slightly toxic[]. The black, globose to depressed-globose fruit is around 5 - 10mm in diameter[] and contains 2 - 3 small seeds[, , ].

An extract of the bark, with the bitterness removed (by drying?) is a common flavouring for soft drinks, baked goods and ice cream[].

Medicinal

Cascara sagrada, the bark of Frangula purshiana, is widely used as a gentle laxative that restores tone to the bowel muscles and thus makes repeated doses unnecessary[, ]. It is often sold in chemists etc[].
The bark is harvested on a commercial basis from wild trees and plantations in western N. America[]. It should be harvested in the autumn or spring at least 12 months before it is to be used medicinally, in order to allow the more violent purgative effect to be mollified with age[, ]. Three year old bark is considered to be the best age[]. It is considered suitable for delicate and elderly persons and is very useful in cases of chronic constipation[].

The bark also has tonic properties, promoting gastric digestion and appetite[, , , , , , , ]. As well as its uses as a laxative, it is taken internally in the treatment of digestive complaints, haemorrhoids, liver problems and jaundice[].
This remedy should be used with caution since in excess it causes vomiting and diarrhoea[]. It should not be prescribed for pregnant or lactating women, or patients with intestinal obstruction[].
An infusion of the bark is sometimes painted over finger nails in the hope that the bitter taste will deter the person from biting their nails[].

The bark contains anthraquinare derivatives, tannin, resins, starch, glucose, and other compounds. When the bark is chewed, it tastes extremely bitter, and may temporarily numb the taste buds[].

Agroforestry Uses:

Plants are sometimes grown in America as an ornamental hedge[].
The tree attracts an abundance of bees and other pollinators during its long flowering season[, ], and the fruits are an important food for songbirds, pileated woodpeckers, band-tailed pigeons, and other wildlife[].

Other Uses

A green dye is obtained from the bark[, , ].
The bark and dried berries have been used as a source of yellow- and saffron-coloured dyes[].
The juice of the fruits,. when combined with alum, produces a green dye that was once used by artists[].

An extract of the bark is used as an ingredient in commercial cosmetic preparations as a perfume, skin conditioner and skin protector[].

Wood - light, soft, not strong. Used for making the handles of small tools[, ].

Propagation

Seed - best sown in the autumn in a cold frame. Stored seed will require 1 - 2 months cold stratification at about 5° and should be sown as early in the year as possible in a cold frame or outdoor seedbed[]. Prick out the seedlings into individual pots when they are large enough to handle, and grow them on in the greenhouse or cold frame for their first winter. Plant them out in late spring or early summer of the following year.
Cuttings of half-ripe wood, mid summer in a frame[].
Cuttings of mature wood of the current year's growth, autumn in a frame.
Layering in early spring[].