Feature Article: February, 2009
In this series of articles I plan to describe various plants that I have grown hydroponically and which I know to be of interest in terms of commercial cultivation.
For the first article I chose Arnica montana, that well-known medicinal plant, the illegal picking of which is endangering the plants of our mountain grasslands. Today I continue with another plant that I have grown in my greenhouse - Stevia rebaudiana Bertoni, the cultivation of which is easy, the yield plentiful and the market, which is only just coming into being, particularly promising.
Indeed, Stevia has several interesting characteristics:
- It is traditionally recognized in many countries for its sweetening and also medicinal power.
- It is easy to grow hydroponically, with attractive results.
- Despite legislation, which continues to be cautious in Europe and the USA, it has every chance of being authorized in the coming years, thus opening up new production alternatives for private and industrial consumption, which will rapidly expand.
- As far as its added value is concerned, we already know that it is extremely profitable, if the figures given on the Internet are to be believed.
This hardy, sub-tropical plant’s flowers are small and white.
Stevia - The Plant
Stevia rebaudiana Bertoni, the variety used, was named in 1899 by the first scientist to profile it, Dr. Bertoni. It is native to the Rio Monday valley in North Eastern Paraguay and belongs to the Asteraceae family. Its principle characteristic is its extreme sweetening power. It is also recognized as having a number of therapeutic properties, particularly for fighting obesity, diabetes and hypertension. It has been used since the mists of time by the Guarani Indians to sweeten mate, their traditional infusion. They call it caá-êhê or "sweet grass."
Stevia principally contains steviosides and rebaudiosides. The intensity of its sweetness and its taste are proportionally dependent on its content of four major diterpenic glycosides found in the leaves, veins and stems: Stevioside (five to 10 per cent), Rebaudioside A (two to four per cent), Rebaudioside C (one to two per cent) and Dulcoside A (0.5 to one per cent). These glycosides are between 40 and 250 times sweeter that the sugar we commonly consume. Steviosides are rather bitter, whilst Rebaudiosides are sweet.
Stevia is a small, dense shrub of roughly 19.7 to 31.5 inches in height when growing wild, reaching up to one yard in height when cultivated. It has intense green lanceolate leaves growing diametrically opposite on the stem. Its flowers are small and white and its tiny seed plentiful yet difficult to germinate. The roots are fibrous and dense. The part used is the leaf, bearing in mind that from the time the plant starts budding its active principle concentration decreases.
It is a hardy sub-tropical plant, which is affected by frost. Its ideal temperature is between 59°F and 79°F. It likes light and should be placed in full sunlight when outdoors. Indoors, MH or HPS lamps are recommended, but neon, which is more economical, can also be used. It needs little in the way of fertilizers so it can be grown on relatively poor land, bearing in mind that it does, however, need significant amounts of phosphate. It must be watered regularly as it likes wet soil rather than dry. It can be harvested up to five times a year for around six years, especially if you care for the roots appropriately and cut the plant right back after each harvest.
I have been growing Stevia successfully for many years but without ever attempting commercial-type cultivation. I have grown it using a variety of hydroponic growing systems. Since the plant likes little nitrogen and more phosphate it is a perfect candidate for biological cultivation.
Growing Stevia is not always easy. For a start you have to germinate the seeds. I have sown them in very large quantities only to achieve limited results. Therefore, I prefer to take cuttings, which is more successful. You can also split it at the end of the season, which seems to be the best means of reproduction. Nevertheless, my plants remain rather small in relation to the Yard-high cultivated shrubs referred to in the literature. Mine seldom exceeds 19.7 to 27.6 inches. It must be said that, as commercial cultivation was not my aim, I did not force the plants but rather was happy to develop shrubs that were just large enough for personal consumption. My plants are, however, beautiful, large-leafed, deep green in color and extremely lush.
Stevia's known enemies are primarily aphids and slugs. The literature talks of Septoriosis, a fungal disease that is believed to be the cause of significant crop loss but which, fortunately, I have not yet experienced. My plants have been affected by whitefly, those little flies that can be particularly destructive. I fought them using Macrolophus caliginosus, one of their natural predators.
It is the old leaves, which are the richest in active principles. The harvest must take place before budding begins. You must, therefore, cut the plant back before August/September, when it starts to bud. It can be cut back often in order to preserve it over time and thus get several harvests in a year. Fresh leaves can be used. They have a rather strong taste, similar to that of licorice. But it is generally used in its dried powder form. It is also converted in some countries and comes in the forms of both a white crystalline powder and an extremely concentrated liquid extract. The leaves are dried in the shade, in a ventilated space and below 104°F, in order to preserve them for as long as possible. In order to prepare it for consumption the well dried, crisp leaves must be crushed in a coffee mill. This leaves you with a more or less finely ground green powder that can be added to coffee and infusions and that can also be used in cooking since it remains stable when faced with pH variations and high temperatures.
If you live in a country where it is forbidden to consume it, you should not do so. But anywhere else, in a private capacity, there is nothing to prevent you from growing your own Stevia plant at home, on your balcony or indoors. The result will be your own plant, the quality of which will be in your control, and which you can use to sweeten your infusions. In order to avoid consuming too much of it, it is recommended that you start with very small doses and adapt it to individual tastes. However, care should be taken when using it for therapeutic purposes; it is always best to consult a doctor before beginning any self-treatment as plants can also be harmful.
Is Stevia dangerous, then? Why should this interest us? Stevia is natural product, which contains zero calories, especially when consumed in the form of dried leaves. It has become increasingly successful over the past few years, primarily due to its sweetening power but also because of its therapeutic properties. Stevia does indeed seem harmless and can be an advantageous replacement for sugar and especially its substitutes such as aspartames, saccharins and cyclamates, the extreme dangers of which are now recognized. It also seems that it can be used for hypertension, digestive problems, obesity and oral hygiene and that it is of particular interest to diabetics, who can safely consume it.
The tribes of South America (Brazil, Paraguay and Uruguay) have been using Stevia for centuries for its sweetening and therapeutic powers with no apparent problems thus far. There is much scientific research today, particularly in Australia and Thailand, which does not show the plant to involve any danger. Nevertheless it remains a risk for the health services in some countries, especially in the West. It is a very controversial plant in Europe and the United States especially, where they insist on its potentially dangerous side and where further in-depth studies are awaited. A European law exists that documents 300DO196 dated February 22, 2000, relating to the refusal of marketing authorization for "Stevia rebaudiana Bertoni, in plant and dried leaf form, as a new foodstuff or food ingredient in accordance with the European Parliament's regulation CE N° 258/97" (gireaud.net/stevia.htm). However, it can be found in various forms to be consumed on the Internet and you can buy the fresh plant from many nurseries throughout Europe.
Some explain its prohibition by the fact that the sugar industry (beet and cane), which is particularly dynamic in our countries, does not wish to be superseded by Stevia. The economic interests are indeed immense.
In 1970, the Japanese government banned the use of synthetic sweeteners and allowed the marketing of natural steviosides. The Japanese have been using Stevia in extract and powder form for nearly 40 years and have thus far found no drawbacks in its consumption. It represents 40 per cent of the sweetener market in Japan and Korea and an increasing number of countries, such as China, Taiwan, Thailand and Malaysia, are consuming it. Large-scale production of Stevia is already underway in Argentina, Brazil, Uruguay, Central America, the United States, Canada, England, Lebanon and Israel among other countries. China and Brazil alone are responsible for 90 per cent of the global production.
Harvests vary between 3,300 and 6,600 pounds per hectare. For Stevia extract alone the market is estimated at 1.5 billion kilos, converted from 12 million kilos of leaves. You can also see the multitude of offers of Stevia in all its forms on the Internet and the plant form already has attractive outlets wherever its sale is authorized.
All this goes to show that this market has huge potential. A hydroponic greenhouse produces around a further 30 per cent of harvests. When used correctly, fertilizers can guarantee a high quality plant, which is rich in active principles. We have the know-how to do this. In 2000, the Department of Pharmacognosy in Toulouse analyzed and compared crops from our greenhouse with outstanding results. The commercial farming of Stevia can thus be viewed as a new alternative to traditional cultivation, which would enable a new income to be generated in a society which needs all its resources to create solid and beneficial wealth.
Other articles by Noucetta Kehdi
