Hypericum's complete botanical name is Hypericum perforatum.
Perforatum is Latin for "perforated." The leaves of Hypericum perforatum, when held to the light, reveal translucent dots, giving the impression that the leaf is perforated. The dots are not holes in the leaf, but a layer of colorless essential plant oils and resin.
The flowers are a bright yellow-orange. The petals are peppered with black dots. When the black dots are rubbed between the fingers, the fingers become red.
Many herbalists say the translucent "perforations" and the black-red spots contain the most active medicinal qualities.
The stem of Hypericum perforatum is unique. As Rudolf Fritz Weiss, M.D., describes it in his book Herbal Medicine:
The plant has two raised lines down the stem. This is something quite unusual in the plant world. Round or four-square stems are the general rule. It is only H. perforatum which has these two raised lines, making the stem appear pressed flat.
Hypericum perforatum is also known as St. John's wort. (As previously stated, wort means "plant.") How the Hypericum perforatum wort got to be named after St. John is not known. Like most unknown things, however, the naming of St. John's wort has a number of perfectly reasonable, possibly even true, explanations.
All seem to agree that the plant's namesake was John the Baptist, not John the Beloved. The stories as to why Hypericum perforatum was named after the baptizer include:
Whatever the reason for its name, by medieval times people believed that if you slept with a sprig of St. John's wort under your pillow on St. John's Eve (the night before St. John's Tide),
the Saint would appear in a dream, give his blessing, and prevent one from dying during the following year.
Hypericum perforatum has a long service to humankind, except where it's been a pesky weed.