Grow stevia for sweet returns
Hortinews continues its series of growing guidlines with a paper on how to grow Stevia. Fell free to ask questions about this in our questions area
Kenya: A sweetener derived from the South American herb stevia (Stevia rebaudiana) is taking the global market place by storm, promising a zero-calorie product that also has the appeal of being natural. The global market for stevia sweeteners has already hit $500 million following US regulatory approval and could reach 10 billion dollars in a few years.
Stevia, which originated in Paraguay but has been used for decades in Japan and other Asian nations, is increasingly becoming an important crop in Kenya. The leaves of this splendid plant are 30 times sweeter than sugar; with zero calories where as pure extract is 300 times sweeter than sugar.
This sweet-honey-leaf herb is likely to become the major source of high potency sweetener for the growing natural food market, in the years to come.Stevia finds its use as a natural sweetener, replacing the chemical sweeteners and even table sugar; the sweetness in leaf is due to the presence of an intensive-sweetening agent called stevioside and the leaf by itself is about 20 to 30 times sweeter than sugar. The leaf has stevioside of 10-12% on dry weight basis.Stevia is a new promising renewable raw material for the food market. The market potential for this natural sweetener is still untapped. Although stevia is not considered an easy herb to grow, it has proved to be quite adaptable and capable of being cultivated in diverse climatic zones. The mature plant grows to 60 cm height. Use the leaves, fresh or dried, directly in hot drinks. You can use ground powder or liquid in baking or desserts.
Propagation and planting
It is best to propagate stevia plants from cuttings or tissue culture
from a plant that has proven to be successful. Growing stevia from seed normally has a very low germination percentage, sometimes only 10% this can be increased by selecting the very dark seeds and plants only those. Through this, germination should exceed 85%. However, stevia grown from seed may or may not be sweet. Avoid over watering after transplanting.
The recommended spacing is 20 cm × 20 cm. the plant requires full sun.
Soil and fertility
Light, sandy, well drained soil with a pH of 6.7 to 7.2.use a standard garden fertilizer. Do not use a lawn fertilizer or fertilizers with high nitrogen. Adding extra Boron will help keep the Stevioside level high. If soil cold be mounded up into a raised bed, this would be even better. Apply a layer of mulch, such as grass clippings, or bark mulch. This will help keep roots cool, preserve water, keep the leave clean from soil and suppress weeds.
Full sun- but not hot weather
Pests and diseases: There are no known diseases and pests in Kenya as yet.
Harvesting: Harvesting entire plant as flower buds appear. Harvest only in the morning for the highest glycoside/ sugar content, whether pinching tips or entire plants. Because it is a member of the Aster family, once flowering has begun, not a single normal leaf will be produced. Removing flower heads is not effective. Failure to harvest plants before several flowers have opened, will allow these flowers to impart a bitter flavor to the leaves. Harvesting is done by cutting the entire plant at the base. With a rubber band, tie loose branches together and hang upside down to dry under warm, dark, drafty conditions for 2 to 4 days. Avoid using food dehydrators or open oven doors as this will tend to cause a bitter flavor. Remove any small branches and grind leaves into powder using electric coffee grinder for 25-30 seconds. Food processors are not as effective because of their slow RPMs. Dried green stevia powder will last almost indefinitely or at least until the next harvest.
Usage: Leaves can be used raw or cooked. It has a very sweet flavor.
The leaves contain ‘stevioside’, a substance that is 300 times sweeter than sucrose. Other reports say that they contain ‘estevin’ a substance that, weight for weight, is 150 times sweeter than sugar.
The dried leaves can be ground and used as a sweetener or soaked in water and the liquid used in making preserves. The powdered leaves are also added to herb teas.
The leaves are sometimes chewed by those wishing to reduce their sugar intake. The leaves can also be cooked and eaten as a vegetable. Many who hesitate to consume artificial food additives may prefer stevia because it is all natural. Stevia is calorie free, and therefore dose not impact blood sugar levels, unlike sucrose (refined sugar). Stevia, when used in place of sugar, may also reduce the incidence of tooth decay.