Professor Curtis tells us that "herbs, during their growth, preserve
their medicinal properties, commencing at the root, and continuing
upward, through the stem and leaves, to the flowers and seeds, until
fully grown. When the root begins to die, the properties ascend from it
towards the seed, where, at last, they are the strongest. Even the
virtues of the leaves, after they get their full growth, often go into
the seed, which will not be so well developed if the leaves are plucked
off early; as corn fills and ripens best when the leaves are left on the
stalks till they die. In the annual and biennial plants, the root is
worthless after the seed is ripe, and the stem also is of very little
value; what virtue there is residing in the bark and leaves also lose
their properties as fast as they lose their freshness. All leaves and
stems that have lost their color, or become shrivelled, while the roots
are in the earth, have lost much of their medicinal power, and should be
rejected from medicine." Seeds and fruit should be gathered when ripe or
fully matured.
Flowers should be gathered just at the time they come into bloom.
Leaves should be gathered when they have arrived at their full growth,
are green, and full of the juices of the plant. Barks should be gathered
as early in the spring as they will peel.
Roots should be gathered in the fall, after they have perfectly matured,
or early in the spring, before they commence germinating and growing.