General Species Description
- Rhamnus purshiana is a medium height, (10m), slender deciduous tree with few branches. The leaves are alternateley spaced, but are so close together they may appear to be opposite. The leaves are simple, oval shaped, with small teeth along the margin. The bark is thin and usually smooth. It is blotchy gray or brown sometimes tinged with red. The bark is very similar to Alnus rubra (red alder).
Leaves
- The leaves of cascara are strongly veined, 8 to 16 cm long, generally oval shaped either round or pointed at the tip. The margins are finely toothed to smooth. They are yellowish to dark green turning yellow in the fall.
Inflorescence/Flowers
- Tiny 5 petaled flowers appear April through June. The cup shaped, greenish, inconspicuous flowers are in clusters on a short stalk at the base of the leaves.
Fruits
- The fruits are small (less than1 cm.). They appear as a few small, round, black, berries on a short stalk at the base of the leaves.
Habitat
- Cascara is found in moist to dry conditions at low elevations. It is most often in a mixed forest of coniferous and deciduos trees. It is often found in shady areas with vine maple (Acer circinatum), and red alder (Alnus rubra). It is fairly common in shrubby secondary growth.
Range
- Cascara is found in low elevations from British Columbia to Northern California. It is usually found west of the Cascades, but can be found in moist canyons as far east as Montana. In Northwest Oregon it is most likely to be found in moist forests of mixed deciduous and coniferous trees often in disturbed areas.
Similar Species
- Cascara can be confused with red alder (Alnus rubra) and they are often found together. Cascara's leaves are more finely toothed (sometimes smooth edged), and the trunk and branches are more slender. Cascara produces a black berry and red alder produces a cone-like fruit which persists through the winter. If you are in doubt about your identification of this plant get a friend(?) to lick the sap. It is intensely bitter and produces a strong laxative effect. You will soon know if the tree you are trying to identify is cascara (not a recommended mode of identification).
Ecological Value
- The fruit is a valuable food source for wildlife. It is not pollution tolerant and could be used as an indicator species.
Human Value
- The bark of cascara has been gathered for many years for an ingredient in laxatives. It was a source of income for this author as a child. The bark should be collected in the spring and summer. Besides being used by pharmacological companies Native Americans have been using the cascara bark's laxative properties for centuries. Usually the dried bark is powdered, boiled in water and drunk by the afflicted person. It can be dried, stored and retain its laxative powers for years. An attractive and useful tree it is seldom used in landscaping as it is prone to aphid attack and does not tolerate pollution.
References
- A Field Guide to the Common Wetland Plants of Western Washington & Northwestern Oregon, edited by Sarah Spear Cooke, Seattle Audobon Society, 1997 -- Flora of the Pacific Northwest, Hitchcock and Cronquist, University of Washington Press, 1974 -- Earth Medicine, Earth Food, Michael A. Weiner, Collier Macmillan, 1980 -- Sunset Western Garden Book, edited by the editors of Sunset Books and Sunset Magazine, Sunset Publishing Corporation, 1991
This page was created by: Rose Wingenbach, August 1998
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