Stevia Comune

Class

Dicotyledoneae

Division

Angiospermae

Family

Asteraceae or Compositae

Order

Asterales

Genus

Stevia

Species

rebaudiana

Description

A perennial herb prized in the agri-food sector for its tender leaves, which contain steviol glycosides that give them a unique sweet flavour. Belonging to the Asteraceae family, like chamomile and the sunflower, it has a compact habit and is profusely branched; it can also be grown both in beds and in pots, requiring full sun and balanced watering without waterlogging.

Varietal description

Stevia is a plant that is grown primarily for its characteristic sweetening power (300 times that of sugar) and for its distinctive flavour. It also has various medicinal and aromatic properties. When growing stevia, it is essential to ensure the plant is always exposed to full sun, whether it is being grown in open ground or in pots. The main growing season is summer, when harvesting takes place; this occurs a few weeks before the plant reaches full bloom in autumn, when numerous flower clusters can be seen. Stevia adapts easily to various soil types, but it is essential to ensure good drainage as it is sensitive to waterlogging. If managed correctly, the plant yields a good harvest in terms of quantity.

curiosity and special features

Of the many species belonging to the botanical genus Stevia, only Stevia rebaudiana has leaves containing steviol glycosides and rebaudioside A, which give the leaves a sweet taste such that they are considered a natural sweetener with a low calorie content and a glycaemic index of zero.

The sweetening components, extracted by drying the leaves and purifying them, are mainly used in the form of a white powder or sugar-like granules, but with a sweetening power up to 300 times greater than that of sugar in hot or cold drinks, as well as in sweets, jams and baked confectionery such as biscuits or tarts. In addition to the food sector, stevia is used in personal care products to combat skin ageing and in the manufacture of toothpastes.

Although it has been the subject of controversy regarding its potential carcinogenicity, the use of stevia as a sweetener has been reauthorised in Europe since 2011, as determined by the EFSA (European Food Safety Authority), which has set the maximum daily intake limit per kilogram of body weight.

Origin and Diffusion

Native to the sandy soils of the Rio Monday valley in Paraguay, where it has been used since ancient times by the Guaraní people – who called it ‘kaa he-he’, meaning ‘sweet herb’ – in traditional natural medicine to sweeten mate tea with its dried leaves. It was first described in the 19th century by the botanist M. S. Bertoni, who gave it the scientific name Eupatorium rebaudianum Bertoni , the specific epithet ‘rebaudiana’ being conferred in honour of the chemist O. Rebaudi, who was the first to analyse the plant’s individual chemical sweetening components; it was subsequently reclassified in the early 20th century by the English researcher W. B. Hemsley under its current name.

It arrived in Europe in the 16th century, but it was not until 2011 that its use in food as a sweetener at specific doses was approved.

Leaf

The slightly tomentose leaves have a lanceolate, oval lamina.

Fruit/product

The leaf has a tender texture and an even colour. The ripening period runs from late spring to late summer. In terms of sensory characteristics, the flavour is delicate with an intense aroma and a taste that combines bitter and sweet notes. The variety is characterised by good organoleptic properties, with a quality profile distinguished by a marked sweetness.

Leaf color

Solid colours.

Plant height

The height of the plant varies from 0.4 to 0.8 m, depending on growing conditions.

Lifespan

Herbaceous perennial.

Suggested planting locations

Stevia is a plant that arouses interest and curiosity; it is suitable for growing in flowerbeds, large pots, open ground, on terraces and in outdoor planters.

Stem/stem

The stem is herbaceous; the plant has no thorns.

Flower

It is arranged in medium-sized panicle-like inflorescences. It flowers from mid- to late autumn, with a flowering period of 25 to 30 days. It is attractive to bees, butterflies and bumblebees.

Growth

A determinate variety that reaches its final height when mature.

Plant habit

The stevia plant has a bushy growth habit with dense foliage.

branching

The abundant branching gives the plant a compact and well-tended habitus.

pH

The pH of the soil or substrate for stevia must not exceed 7.0, with ideal values between 5.0 and 6.8.

soil preparation

For early spring planting, it is advisable to carry out a light digging to a depth of 20–30 cm, removing any weeds, residues from previous crops and large stones, then work in organic or slow-release chemical fertiliser and further break up the clods using a spade. To improve drainage of excess water and prevent waterlogging, continue by creating a raised bed through gentle mounding of the soil, then carefully level the surface.

Throughout the growing season, continue to remove weeds from around the plant to prevent them from hindering its normal growth.

sun exposure

An exposure of the plant in full sun, afternoon sun, sheltered from the wind and combined with adequate irrigation is essential for luxuriant growth.

Ideal climate and temperature

The ideal temperature is between 15 and 30 °C; as it does not tolerate low temperatures, if grown in a pot, it is advisable to avoid placing it outdoors until the risk of frost has passed, whilst for growing in a flowerbed in areas with harsh winters, the roots should be protected by mulching.

Use

Thanks to the sweetening properties of its foliage, it is valued and used in the following areas:
Agri-food Medicinal / herbal medicine Herbs

Hardiness

A moderately hardy variety; it is sensitive to low temperatures and waterlogging, but with the right cultivation practices it will produce excellent results.

Soil/medium

It adapts to a variety of soil conditions; however, for optimal growth, choose a medium-textured or sandy soil rich in organic matter and, above all, well-drained, as stevia roots are sensitive to waterlogging; for growing in pots or containers, we recommend using a high-quality peat-based potting compost suitable for vegetable gardening.

Maintenance

Cultivation of stevia is fairly easy, requiring an overall average level of management effort, paying particular attention to temperature and irrigation factors.

cultivation tips

Below are some specific cultivation tips and guidelines for this variety, aimed at achieving the best growth and yield results:
Balanced fertilisation Avoid over-watering Move outdoors once there is no longer any risk of frost

Intercropping/combination

If grown in open fields, we recommend intercropping with radishes.

planting

When growing in a flowerbed, given the variety’s growth habit and profuse branching, plant at a density of 11 plants per square metre so that each plant has sufficient space to grow to its full potential. Transplant the plants onto the crest of a raised bed, positioning them so that the root collar is above ground level, and water immediately afterwards; It is also recommended to transplant hardened-off seedlings – that is, those acclimatised to outdoor temperatures – to avoid stress caused by changes in environmental conditions, and to ensure they have intact root systems.

pruning

Prune the plant by removing any woody or dry parts that form during the stevia growing cycle; if the plant is grown in an open field, cut it back to about 10 cm from the base in the autumn.

Following the spring-summer harvest, before flowering, we recommend treating the plant with a copper-based product to disinfect the cuts caused by pruning.

Reproduction/Propagation

Propagation can be carried out by sowing seeds – either in the open ground or in containers – by dividing the clump, or by taking cuttings.

Irrigation

When growing stevia, it is important to ensure that the water supply is well balanced to its water requirements, avoiding harmful waterlogging and increasing the frequency of watering during the summer months. Use rainwater, or alternatively canal water or tap water with an optimal sub-acidic pH, watering either manually or via a drip irrigation system or sub-irrigation.

Water immediately after transplanting and support the plant, which may be more exposed to water stress in its new location, avoiding periods of drought whilst at the same time not overwatering to prevent asphyxia and root rot. Thereafter, allow the soil or growing medium to dry out slightly between waterings, keeping it consistently moist but not waterlogged. Watering should take place in the morning to ensure the leaves have had time to dry out before evening, thereby improving the plant’s defences against potential attacks by pathogens.

If sowing seeds, moisten them to aid germination; furthermore, after burying them completely and covering them with a layer of growing medium and inert material, keep the soil moist until the shoot emerges.

Fertilization

Carry out a background fertilisation with slow-release organo-mineral fertiliser during pre-transplant soil preparation. Stevia does not have great needs in terms of nutrients, but it is useful to intervene every 30 days from the vegetative resumption; it is advisable to use a specific fertiliser for vegetable garden plants, which is water-soluble, i.e. to be diluted and distributed in suitable doses in the irrigation water, avoiding overdoing it in the early stages of cultivation.

Edibility for humans

Stevia leaf extract is edible when taken properly.

advise 1

This plant is sensitive to low temperatures, soil conditions and various fungal diseases. You should therefore pay close attention to watering, the time of transplanting and various adverse conditions.