The following is an excerpt from the Hibiscus article found in New World Encyclopedia.
Hibiscus is the common name and genus name for a group of about 250 species of shrubs, trees, and herbaceous plants in the mallow family (Malvaceae), characterized by alternate leaves and generally large and showy, often bell-shaped flowers with stamens united into a tubular structure surrounding the style. Hibiscuses typically have five sepals and five petals, or the sepals may be basally connected to form a calyx with five teeth. Also known by the common name of rosemallow, this genus includes such well-known members as rose of Sharon (Hibiscus syriacusand) and China rose (Hibiscus rosa-sinensis), with roselle (Hibiscus sabdariffa) being the most commonly known species for medicinal purposes.
Hibiscus is used medicinally for a wide variety of ailments. Most commonly used medicinally is H. sabdariffa, known as roselle, but also popular are H. rosa-sinensis (common hibiscus, China rose) and H. syriacus (rose of Sharon). Roselle is said to lower fevers and high blood pressure, relieve coughs, increase urination, and kill bacteria. China rose is used primarily for respiratory problems, but also for skin disorders and to treat fevers. Rose of Sharon is used externally as an emollient to soften and soothe the skin, as well as used internally for digestive disorders (Kim 2005).
Hibiscus, especially white hibiscus, is considered to have medicinal properties in the Indian traditional system of medicine, Ayurveda. Roots make various concoctions believed to cure various ailments.
Other healing properties attributed to hibiscus preparations include for hair loss, relief for menstrual cramps and for the pain in childbirth. Studies have shown hibiscus to be hypotensive (lower blood pressure), antispasmodic (suppress spasms), and antibacterial, as well as effective against tuberculosis (Kim 2005).
Since some species are used as abortifacients (induce abortions), preparations should not be used by pregnant or nursing women (Kim 2005).
Many commercial herbal teas contain hibiscus. roselle (Hibiscus sabdariffa) is used as a vegetable and to make herbal teas and jams (especially in the Caribbean).
Hibiscus is a primary ingredient in many herbal teas. In Mexico, the drink made with hibiscus is known as Jamaican water or agua de Jamaica and is quite popular for its color, tanginess, and mild flavor; once sugar is added, it tastes somewhat like cranberry juice. Dieters or persons with kidney problems often take it without adding sugar for its beneficial properties and as a natural diuretic. It is made by boiling the dehydrated flowers in water; once it is boiled, it is allowed to cool and is drunk with ice (Vinculando 2005).
In Egypt and Sudan, roselle petals are used to make a tea named after the plant karkade.
Dried hibiscus is edible, and is often a delicacy in Mexico.
Source: New World Encyclopedia, Jan 2009