Comments: There is indirect evidence, obtained from reliable sources, of plant collecting from wild populations for the plant trade. Collingwood and Brush (1965) stated that the bark is collected extensively from trees in southern British Columbia, western Washington and Oregon, and northern California: "There is an annual harvest that comprises a forest industry of major importance to some rural regions." The bark is collected as strips peeled lengthwise.
Habeck (1992) reports the most effective collecting period to be mid-April until the end of August; the U.S. Forest Service (1963) stated that the peeling season usually runs from March through July. According to Sievers (1930), the collecting season opened about the end of May and closed before the rainy season set in. Veninga and Zaricor (1976) considered the collecting season to be in summer and continue until the rain ends in a region, as hot weather draws the sap from the bark into the inner tree. However, Clay-Poole (1999) reports that native North Americans considered it best to harvest the bark in late October and early November after the sap had descended down the trunk.
Collingwood and Brush (1965) stated that the demand is growing (even in competition with synthetic products), and that each year the bark gatherers must go farther back into the mountains. However, Hill (1998) reported that the chemical found in the bark can now be made synthetically, and for this reason a British Columbia law was removed that used to protect the species. In contrast, Tyler (1995) stated that some plant materials contain a large number of active principles and that purification may eliminate certain useful ones. He gave cascara (Frangula purshiana) as one of several examples where, "besides ... the isolation and purification of specific constituents is simply not necessary. It would be a waste of time and money to purify such herbal remedies ..."
Collingwood and Brush (1965) stated that in accessible areas, bark-peeling inroads have kept the average diameter down to 6 inches or less, and that such trees provide the major source of harvest. Veninga and Zaricor (1976) stated that the bark is collected properly by first cutting down the tree, so that a new tree will grow from the roots, but that if the tree is left standing and the bark stripped, it will die without resprouting. According to Collingwood and Brush (1965), a great deal of stump sprouting is precluded because the trees are not cut down after the bark has been peeled. Stumps sprout vigorously (coppice), producing 4 to 15 stems. "For this reason there is no dearth of wild bark at present."
However, Sievers (1930) reported that the tree will develop new bark if collectors in removing the bark allow enough to remain to prevent the tree from dying, and that this practice would prolong the natural supply of this valuable drug which was gradually being exhausted. Turner (1997) noted that Northwest Coast native peoples traditionally used the bark of many tree species for medicine, including cascara. Almost always, the bark pieces of the species utilized were cut in a narrow vertical strip from the sunrise side or river side of the tree. This practice was to allow the tree to continue to grow; the sunrise side was said to heal more quickly.
Michael McGuffin (in a meeting with Botany staff at TNC/ABI on Jan/10/2000) said that the American Herbal Products Association (AHPA) fairly recently surveyed its members regarding their trade in various species. He stated that their figures should be considered preliminary, and in general might include some double counting (if one company supplied another), resulting in over-reporting by as much as twice the actual usage. Thus a maximum total of 150,000 pounds of dried cascara bark per year may have been supplied in 1990, 1991 and 1992 by those AHPA members who responded, or the total for this species might be only half the above, 75,000 pounds per year (McGuffin email to TNC/ABI, Jan/27/2000). The AHPA has included this species in a more definitive planned tonnage survey for the 1999 season (AHPA letter to TNC, Jan/11/2000). He considered the cascara-sagrada trade an essentially steady rather than fluctuating market, and significantly in the market because the amount is relatively large, while noting that a few other species (particularly senna) were preferred as herbal laxatives. He was unaware of this species being cultivated (but will inquire), and thought the entire supply was probably from more or less wild sources (although likely with a well-organized/managed harvest because of company desire for stability in supply).
According to Habeck (1992), in a single [unstated] year 5 million pounds of dried cascara bark from the Pacific Northwest were processed by pharmaceutical companies. Prescott-Allen and Prescott-Allen (1986) reported (according to Norse 1990) that in Washington state, young men in interviews [year unstated] said that on a good day they could each bring in 280-300 pounds [presumably of fresh peeled bark strips -- Hill 1952, Veninga and Zaricor 1976]. The U.S. Forest Service (1963) stated that the bark's wet weight is about twice the dry weight.
The species was included in a list of the principal competing species on Pacific Northwest commercial forest land (Norse 1990), and the Vegetation Management Research Cooperative (VMRC) has selected this species to include in volume 3 (in preparation) of their autecology manuals on "problematic competitor plant species for forest vegetation managers" concerned with producing crop trees by reforestation in Washington, Oregon and northern California (VMRC 1999). Moore (1993) said that the species is especially common in heavily timbered forests.
