| PROTECTED TREES OF THE DISTRICT of METCHOSIN | ||
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CASCARA (Buckthorn)
(Rhamnus purshiana)
RANGE
Cascara is native to western North America, occurring in British Columbia on the southern part of the coast, Vancouver Island and in the Columbia Valley. It ranges south to northern California and east to Montana.
Young cascara in fall colours at Blinkhorn Nature Park. Photo by Moralea Milne
HABITAT AND LIFE HISTORY
Cascara is a shade tolerant inhabitant of mixed woods and a coniferous forest understory tree. It prefers nutrient rich soils with moderately high summer moisture conditions. It tolerate fluctuating groundwater levels and can be found in riparian areas and wet sites as well as in drier locations, at low to middle elevations. It is often associated with lady fern, sword fern, red alder and vine maple.
Cascara is found in widespread and scattered occurrences but is never very abundant. It is a winter browse food for deer, elk and bears but is not a preferred food item. The fruits are consumed by birds, including band-tailed pigeons and ruffed grouse.
DESCRIPTION
Cascara leaves and flower clusters. Photo by Virginia Skilton.
Cascara is a deciduous, deep rooting, small tree or shrub that can reach 15 m but is more commonly 5-10 m in height. The trunk is usually 20-30 cm in diameter and the bark a silvery-grey colour, smooth when young and becoming scaly with age. Inner bark is a bright yellow and the sapwood is orange. The bark is aromatic and has an extremely bitter taste.
The flowers are inconspicuous, 3-4 mm long, in clusters in the leaf axils. The fruits are dark blue-purple berries, 5-8 mm across, apparently edible but perhaps with laxative qualities.
Cascara flowers. Photo by Virginia Skilton.
The leaves are alternate, egg-shaped to oblong, finely toothed with 10-12 pairs of prominent veins. The leaf surface appears rippled. The leaves turn a lovely yellow in fall.
REPRODUCTION
Most reproduction is through seeds that are dispersed by birds and squirrels, having traversed through their digestive tract.
Trees are able to resprout from crowns after low-intensity fires and can vegetatively reproduce from layering.
THREATS
Cascara bark has been used since the late 19th century in natural laxative preparations, this has resulted in overharvesting in many areas. Threats to cascara have diminished with the development of synthetic drugs, although there are few mature tress remaining.
CULTURAL USES
First Nations used cascara for its laxative properties; stripping the bark and allowing it to cure for a year before being pulverized and boiled. Fresh bark can cause severe nausea. Other medicinal uses includes as a wash for sores and swellings, treating heart and internal strains and lately, as a wash for cold sores. It was also used to flavour some products and in the production of yellow and green dyes.
The fine-grained wood is excellent for wood turning.
Cascara wood turned container by Lea
PROPAGATION
Seed can be collected from July/September. Separate the fruit from the seeds, dry, store seeds in a sealed container in the refrigerator or at 5ºC.
Needs a cold, wet stratification, at 1-5ºC for 90-115 days or sow outdoors in the fall.
Hardwood cuttings can be taken in September and October
Cascara can be layered in situ (branches nicked and pegged into soil, where they will produce roots), layer in early spring. Keep soil moist.
Further Information and References
Douglas, G. et al, 1999. Illustrated Flora of British Columbia, Volume 4 (Dicotyledons). Crown Publications, Victoria, BC. http://www.for.gov.bc.ca/hfd/library/documents/treebook/index.htm http://www.fs.fed.us/database/feis/plants/shrub/rhapur/all.html
http://depts.washington.edu/propplnt/Plants/cascara.htm
www.greentimbers.ca/index.php?option=com_content&task=view&id=68&Itemid=35
Lea: http://teaktalks.blogspot.com/2005/07/on-cascara.html
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