Blue flag (_Iris versicolor_) is a native perennial plant of common
occurrence in swamps and marshy situations throughout the eastern half
of the United States. The underground stem (rhizome) and roots are the
parts of the plant used medicinally.
Blue flag responds readily to cultivation when placed in a rich, moist,
and rather heavy soil. It is readily propagated from divisions of old
plants, which may be set 1 foot apart in rows spaced conveniently for
cultivation. If the plants are set in August or September, the crop
may be harvested about, the last of October in the following year.
The roots may be turned out with a deep-running plow, and after being
thoroughly washed and the larger clusters broken up they should be
thoroughly dried. Artificial drying at low heat is usually desirable.
Yields at the rate of 3 or 4 tons of dried root per acre have been
obtained from small plats. The prewar price paid to collectors varied
from year to year and usually ranged from 5 to 10 cents a pound. The
price in June, 1920, was 35 cents a pound. This crop does not appear to
be very promising, owing to the relatively small demand for the root