‘Sacred bark’

Leaves and berries of the Cascara tree (courtesy Oregon State University, landscape)

Cascara is a medium-sized deciduous tree or large shrub that can reach 33-feet tall.

Spanish conquerors found several native people using the bark in the 1600s. The conquerors named the mottled gray bark “Sacred bark.”

Processed bark became famous in the 1800s. It was exported to the European markets.

As one might have guessed, the Pacific Northwest native tree populations declined through overharvesting.

Rising Star

Who would have thought that a local bark could become famous?

The commercial product was called ‘Cascara sagrada’ and it was used in more than 20 percent of the U.S. products in the late 1990’s. The industry at that time had an estimated value of $400 million.

In May 2002, the U.S. Food and Drug Administration banned the use of this tree in over-the-counter drug products and found the use potentially carcinogenic.  

Cascara flowers (courtesy of Oregon State University, Landscape)


The outer bark has light splotching (sometimes from lichens). The inner bark is smooth and yellowish. Exposed inner bark will oxidize and turn brown.

Fresh cut bark is intensely bitter and will overpower the taste buds—for hours. Fresh cut, dried bark will cause vomiting and violent diarrhea.


The sickly, sweet fruit can be eaten cooked or raw. The berries are deep purple or black with yellow pulp. The berries usually contain two or three hard, smooth seeds.

In the past, the food industry used cascara as a flavoring agent for liquors, soft drinks, ice cream, and baked goods.

NOTE: The fruit and honey both have a laxative effect.

When to Collect

Bark collected in the spring or early summer can be easily peeled off the stem. Bark will be aged and dried for at least a year before use.


Cascara tree bark is a strong laxative that should be used carefully.

It can induce labor in pregnant women and transfer active compounds to nursing infants.

There are several precautions about this bark and warnings that it may be carcinogenic.  

Where Found

This tree is native to northern California up to British Columbia and from the Pacific Coast east into Montana. Leaves are oval up to 6-inches long with fine edge serrations. Small, green flowers develop into blue-black fruits.  

Cascara plant grow near streams in mixed forests. Check under big leaf maple trees–they are often an understory there.

Safe Uses

The fall yellow leaf color is pleasant (color varies based on light) and branching is interesting. Cascara does not adapt well to urban settings and is better in a woodland park or garden.

Cascara is a nice ornamental that can help prevent soil erosion and provide wildlife food and habitat. The fruit is a favorite of the Pileated woodpecker. Bears, raccoons, deer, and other wildlife also consumed the berries.

–Oregon State landscape plants (https://landscapeplants.oregonstate.edu/plants/rhamnus-purshiana and https://landscapeplants.oregonstate.edu/plants/frangula-purshiana)
–Wikipedia, Rhamnus purshiana (https://en.wikipedia.org/wiki/Rhamnus_purshiana)
–Native Plants of the Pacific Northwest (http://nativeplantspnw.com/cascara-frangula-purshiana/)
–Trees & Shrubs for Pacific Northwest Gardens, Grant & Grant

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