The Stevia Plant

Stevia rebaudiana Bertoni is a small, shrubby plant and belongs to the family of composite flowers (Asteraceae or Compositae). The stevia plant is native to Paraguay and prefers sandy soils near water. In the wild, the stevia plant can reach a height of up to 75cm.

Stevia rebaudiana Bertoni is the Latin name of the Stevia plant. This consists of the generic name Stevia, the species name rebaudiana and the subspecies name Bertoni. There are over 150 other Stevia plant species, of which only the Stevia rebaudiana species contain the sweet Steviol glycosides. This Stevia plant species is therefore also called honey leaf, honey herb, sweet herb by the indigenous population, the Guarani and Mato Grosso Indians in Paraguay and Brazil. In the Guarani language in Paraguay the sweet herb is also called caá jeé, kaá heé, or Yerba Dulce.

The botanist Moisés Bertoni was the first to discover the sweet ingredients of the stevia plant. The individual components of the stevia leaves, the steviosides, the rebaudiosides A to F were analysed and broken down by the chemist Ovidio Rebaudi.

The origin and distribution of stevia

The highlands of Argentina, Brazil and Paraguay from 22nd to 23rd southern latitude and from 55th to 56th western longitude are the natural home of the Stevia plant. The soil composition and the moderately humid climate in the border area between Argentina, Brazil and Paraguay, with an annual average temperature of 21°C and an annual precipitation of 1500 to 1800 mm, form an ideal distribution area for the Stevia rebaudiana plant genus. The sweet Stevia species grow particularly well on the sandy, acidic and clayey plateaus of the Amambai, in the state of Mato Grosso do Sul in the border area between Brazil and Paraguay.

Today the stevia plant is cultivated in Latin America, South-East Asia and almost all continents of the world for the production of sweet components, steviol glycosides and rebaudiosides. The sweeteners are extracted in a complex extraction process.

The Stevia Botany

The Stevia rebaudiana plant is a shrubby plant and belongs to the family of composite flowers (Asteraceae or Compositae). The Stevia plant is native to Paraguay and prefers sandy soils. In a frost-free climate the Stevia plant develops a strong rootstock from which perennial stevia shoots up to one meter high grow. The stevia plant belongs to the shallow root family, i.e. the stevia roots spread plate-shaped in the upper soil layers.

The Stevia leaf

The stems of the stevia plant develop into lancet leaves, sickle-like, pointed toothed leaves. The light to dark green stevia leaves, up to 8 centimetres long, are arranged opposite each other and have plant hairs on the leaf surface. Depending on the Stevia plant species, the Stevia leaves can be egg-shaped or diamond-shaped.

Ingredients of dried Stevia rebaudiana leaves

The leaves of Stevia rebaudiana contain the sweet-tasting components, the steviol glycosides or steviosides. These give the stevia plant its sweetness. Steviol glycosides and rebaudioside A have the greatest importance. Other sweeteners such as dulcoside A, rebaudioside B, C, D, E, F and steviol bioside also occur in the stevia leaves of the plant. Based on the dry weight of the stevia leaves, a stevia leaf contains 5-10% stevioside, 2-4% rebaudioside A, 1-2% rebaudioside C and 0.4-0.7% dulcoside A. Dried stevia leaves are 20 to 30 times as sweet as sugar and the extract obtained from them, steviol glycosides up to 300 times sweeter.

Further ingredients of the Stevia leaves

Stevia rebaudiana leaves are a good source of proteins and carbohydrates. The content of inorganic minerals is attributed to the high ash content. The minerals and secondary plant substances contained in the stevia leaves are also important.

The Stevia Flower

The stevia flowers are arranged in an irregular inflorescence and are about 7-15 mm in size. The flower heads of Stevia rebaudiana are terminal and grouped into umbels. These consist of white 5-flowered cylindrical flower heads. A Stevia rebadiana shoot can have between 10 and 200 flower heads. The fruit of the Stevia plant is thin and long and has 4 to 5 edges.

A characteristic of Stevia flowers is their self-sterility (self infertility). This is what plants are called that cannot fertilise themselves. After pollination with pollen of the own genus (genotype) the seed formation does not take place. The wind does this under natural conditions by carrying the flower pollen of the Stevia flowers from Stevia plant to Stevia plant and only so seed formation is possible. This type of sexual reproduction is also known as wind pollination.

The Formation Of Stevia Seeds

The Stevia seed is approx. 3 mm long and belongs to the family of the lonesome indehiscent fruit (Achaene, as well as the dandelion). The seed of the Stevia plant is equipped with a flyable feather-like hair crown. After the ripening process, the stevia seeds, which are formed in seed calyxes, fall out easily.  Stevia is a light germ and on moist soil the germination time is 20-25 degrees to 14 days at a germination temperature.

Stevia seed is known for its low germination rate of 12 to 15 percent, even with optimal seeds. Another much simpler species is the vegetative propagation of the stevia plant via cuttings. In many nurseries and garden centres you can buy a Stevia plant today and keep it in your garden in summer.

The vegetative propagation and cultivation of Stevia

The vegetative propagation of the Stevia plant via cuttings is much easier than germinating Stevia seeds.