Cascara, or cascara sagrada (_Rhamnus purshiana_), is a small tree 20
to 30 feet high, native to the Western part of the United States, and
found most abundantly in a narrow belt along the Pacific slope from
northern California to southern British Columbia. The bark from the
trunk and branches is the source of the drug, for which there is a
constant and steady demand.
Plantings which have been made in the Eastern States indicate that this
tree may probably be grown along the Atlantic slope in the Piedmont or
foothill belt from Pennsylvania to Georgia. The trees have been found
to grow better in clay loam than in either sand or clay. Propagation
from seed is easy, but the seeds should be planted in the fall soon
after they ripen or stratified in sand until used, since germination is
very poor if the seeds are allowed to become dry. The seeds are sown
in a seed bed under shade in drills 8 inches apart and covered about 1
inch deep. The seedlings reach a height of 10 to 15 inches the first
year, and in the following spring before the leaves appear they are
set in the field 6 feet apart each way. It is advisable to cultivate
frequently, in order to keep the weeds down and to maintain a shallow
surface mulch.
If the trees are pruned properly, a crop of bark may be harvested each
year without killing the whole tree, as is done in collecting the bark
from wild trees. At the time of transplanting, the trees are cut back
to a straight stem about a foot high, from which all except the four
uppermost buds are removed. The branches which afterwards develop
from these buds are later deprived of their lower side shoots, thus
causing the tree to grow a head of four long, stout branches instead
of a single straight trunk. When the trees are large enough to yield a
crop of bark, the longest of the four branches is cut off early in the
spring flush with the trunk and a new branch is allowed to grow in its
place. This process may be repeated yearly, removing only the largest
branches of each tree in any one season.
The bark on the cut-off branches is divided with a sharp knife into
lengthwise strips of about an inch or two in width, which may be
readily pulled off. It is then dried carefully at a low temperature
in the shade and broken into small pieces to facilitate packing and
handling.
The price paid to collectors for cascara bark, which before the war
usually varied from 1 to 4 cents a pound, in June, 1920, was about 10
cents a pound. So long as a supply of the wild bark continues to be
available it is doubtful whether cascara can be cultivated at a profit.