Stevia rebaudiana is a is plain looking plant that has been used as a natural sweetener as well as a medicinal plant.  It  grows to 2-3 feet and resembles mint but does not share mints ability to spread rampantly.  It is preferable to  propagate this plant by stem cuttings which take root easily.  Seeds have a low germination rate.  Its unrefined leaves are up to 15 times sweeter than sugar while in its more refined form the white stevia powder is up to 300 times sweeter than sugar.  it can also be purchased in liquid form.   It contains virtually no calories because of the unusual structure of its glycoside molecules.

It has been used safely as a sweetener by the people of Paraguay and Brazil for centuries. It doesn't cause a rise is blood sugar and may even regulate blood sugar levels.  It does not promote the growth of  unhealthy yeast and fungi and is believed to improve digestion as a result of stimulating the pancreas.  Stevia contains up to 10% stevioside, a substance which has been shown in studies to actually inhibit the development of plaque so not only does stevia not contribute to the formation of cavities it may actually prevent them.

Some people think it has a slightly anise like flavour while I've heard others just say it has a "green" taste to it.  It may take some getting used to but is a great healthy alternative to chemical sugar substitutes.