Growing Your Own Stevia Rebaudiana
Stevia Rebaudiana is a small shrub native to locations of Northeastern Paraguay and adjacent area of Brazil. It flourishes in the sandy soil of this elevated terrain and may grow to a height of 80 cm when it is fully mature. While native Indians of the Guarani Tribe appear to have used the leaves of this herb as a sweetener since pre-Columbian times, it was not until 1887 when a South American natural scientist named Antonio Bertoni discovered it.
Growing Stevia Plants in your home herb garden is not difficult as long as one follows a few basic guidelines that seem to work well for this unique and controversial herb, stevia.
In India stevia is best grown in the Northern states of Himachal Pradesh and, Uttarakhand. In the North Eastern States of Arunachal, Assam and Mizoram. In the Southern States of Karnatica, Andhara Pradesh and parts of Tamil Nadu. In the Central State of Chittishgarh.
Plant Type: Tender Perennial, an annual in most areas
Planting Zones: All over India where the summer temperature is between 20 ? 25° C (It sensitive to low winter temperatures).
Stevia rebaudiana is a tender perennial, native to semi-humid subtropical regions of Paraguay and Brazil. Wild plants occur on acid soils that are constantly moist, but not inundated, often near the edge of marshes or streams where the soil is sandy. In the garden, too, Stevia doesn't like to dry out, but standing water will encourage rot and disease. Stevia can be a successful garden plant in most climates with the use of a few simple techniques. Raised beds or hills prevent "wet feet," while an organic mulch and frequent watering ensure a constant supply of moisture.
Soil Preparation
Stevia is tolerant to most soil types, but it prefers a sandy loam or loam. Any well-drained soil that produces a good crop of vegetables should work fine. Incorporating organic matter is the best way to improve heavy, high clay soils. A rich compost made with leaves, grass, hay, kitchen waste, manure, and other organic residues will improve soil structure and supply nutrients.
Stevia occurs naturally on soils of pH 4 to 5, but thrives with soil pH as high as 7.5. However, Stevia does not tolerate saline soils.
While a good compost usually satisfies nutrient requirements, soil testing or plant symptoms must be noted for deficiencies. It is recommended to use low nitrogen or organic fertilizers. Excess nitrogen promotes thick growth with poor flavor. Bone meal, blood meal, cottonseed meal or dried manure provide nitrogen that is released slowly. Rock phosphate or bone meal provide phosphorous. Rock phosphate, bone meal, offer a wide range of trace minerals. For maximum nutrient availability, work organic fertilizers into the soil a few months before planting, or mix with compost. For poor fertility soils, it is recommended to incorporate 3 to 5 kg of cattle manure per square meter. When using chemical fertilizers, a low nitrogen formula such as 6-24-24 is recommended in a split application - at planting time and again in mid summer.
Unless your soil is very sandy, raised beds are ideal for Stevia. A raised growing surface prevents standing water and reduces compaction. Beds should be 3 to 4 feet wide and 4 to 6 inches high. With the help of a spade mix the soil in the whole area thoroughly, then mark bed boundaries with string. Dig soil from the paths, 1 to 3 feet wide, and toss onto the beds until they reach the desired height. Beds may be left in place permanently. By walking only on paths, soil compaction is reduced.
Periodical toping up should be undertaken during the growing season, by pulling extra soil up around the plants with a hoe. This will help to remove the weeds and drain away surface water that could encourage disease.
Getting Started
Stevia rebaudiana seeds are rarely available because of production problems and poor germination, so plants are generally used for growing.
Seedlings grow slowly, so allow 7 to 8 weeks from seed to transplanting. Only black or dark brown seeds are viable. A tan or clear color suggests they are empty shells, lacking an embryo. You can verify this by slicing some seeds in half. Good seeds will be solid and white inside. Even firm, black seeds tend to lose viability rapidly. A germination test will indicate what percentage of the seeds are likely to sprout. Place 10 or more seeds on a wet paper towel. Fold the towel in half 3 times, then slip it into a plastic bag kept at 20 ? 25° C. Count the sprouted seeds after 7 days and divide by the total number of seeds you were testing, then multiply by 100 to get the germination percentage.
A plastic flat covered by a clear plastic dome, available from garden retailers, makes a good germination chamber when placed beneath a growing light. Place a thermometer inside and maintain a 20 ? 25° C temperature by adjusting the level of the light. Use small containers (with drainage holes) or plastic cell packs filled with standard potting soil. Place 3 or 4 seeds on the soil surface in each container and cover with a thin layer (about 2 mm) of horticultural vermiculite. Water from below as needed by pouring water into the tray. Seedlings should emerge in 1 to 2 weeks. Thin to one plant per container. Extra seedlings may be transplanted to empty containers.
Plant Care
In general, Stevia should be treated as a vegetable crop. When hot weather sets in, usually a month after planting, beds should be mulched 3 to 6 inches deep with organic residue such as grass clippings, chopped leaves, straw, hay, or compost. This will protect the shallow feeder roots and hold in moisture. Plant growth is slow at first, accelerating by mid summer.
A consistent moisture supply is important for Stevia. Irrigate once or twice a week, whenever rain fails to water the plants. Sandy soils require more frequent irrigation. Trickle irrigation is ideal, ensuring consistent moisture levels without wetting leaves. A simple and effective system is to use perforated PVC pipes. Place one length between the two rows of plants, beneath the mulch. Attach to a garden hose and turn the water on at a trickle for a couple of hours.
Side-dressing is usually not necessary, but low nitrogen or organic fertilizer may be applied in the summer as plant growth begins to accelerate. Excess nitrogen causes tender growth and reduced leaf sweetness. It is recommended to apply 10-10-12 foliar fertilizer directly on leaves at 30 and 60 days from transplanting.
Stevia stems are prone to breakage during high winds. It is advised to pinching tips out every 3 to 4 weeks for the first month to encourage side branching, resulting in a bushier plant. Grow in a protected area if possible. Supporting the plants with a "corral" made from strings tied to stakes help the branches from braking.
Stevia may be affected by two lesion-producing fungal diseases, Septoria steviae and Sclerotinia sclerotiorum. With Sclerotinia, dark brown lesions form on stems, near the soil line, followed by wilting and eventual collapse of the plant. Stevia plants are usually full grown before diseases appear. As harvest time nears, commercial growers watch plants closely and harvest the entire crop at the first sign of disease. Meticulous weed control (by hand) permits strong growth, which helps plants resist disease. Humid, wet weather and standing water favor the development of fungal diseases, making raised beds or hills a preventative measure. Additionally, avoid wetting leaves during irrigation. Stevia is usually the last plant insects will feed on, so pests are seldom a problem outdoors. Aphids, thrips, and whiteflies can cause damage in heavily infested greenhouses.
Some important tips
· Stevia Plants prefer well drained, loamy soil with an organic content of 2.5% or more.
· Wait until the danger of frost is past and soil temperatures are well into the 50s and 60s before transplanting them into your garden.
· Place the Stevia plants in rows 60 cm apart and 30 to 40 cm between plants.
· Keep Stevia plants moist but not soggy with frequent light watering preferred. A layer of compost or mulch helps to conserve moisture.
· Stevia Plants respond well to "slow release" or low nitrogen fertilisers.
Harvesting
Harvest should be done as late as possible, shorter fall days intensify the sweetness of the stevia plants.
Use fresh leaves for tea or eat a few right off the plant. They taste great with mint leaves. Sweetness (Stevioside content) is greatest just before flowering, which is triggered by short day lengths. The onset of blossoming ranges from mid summer to late fall. Plants should be harvested before the first frost or as soon as blossoming begins, whichever comes first. Cut entire plants just above ground level. When growing Stevia as a perennial or for early harvests, clip the plants 6 inches from the ground so they will survive and re-grow. Harvest in the morning, after dew has evaporated.
Plants are easily dried by hanging upside down in a dry, warm, drafty location. Bunch a few plants together and bind at the stem end with a rubber band, then slip a paper clip bent into an "S" shape under the rubber band. Hang by the other end of the paperclip. If you have lots of plants, hang them from strings or wires strung across the ceiling. After a few days, rake leaves from the stems with your fingers and gather for storage in a clean container such as a glass jar. They keep well for years. An alternative method is to strip fresh leaves from stems and spread on elevated screens in the sunshine, on a day with low relative humidity (less than 60%). If drying takes 8 hours or less, very little Stevioside will be lost. While whole leaves are great for making tea, it's easy to turn them into Green Stevia Powder with a kitchen blender, food processor, or coffee grinder with metal blades. With the blender bowl half full, process dry leaves at high speed for a few seconds. Collect the fine powder for use in recipes calling for Green Stevia Powder. Use a clean glass jar for long-term storage.
Propagation and Container Growing
Stevia stem cuttings root easily without hormones, but only under long day conditions. Stevia cuttings root most easily during the long days of spring. Cuttings should be taken in March for transplanting in May or June.
Coarse or medium grade horticultural vermiculite works well for rooting Stevia. A peat-lite mix that includes bark, especially for outdoor propagation beds. Coarse, clean sand may be used as well.
Place small pots, or cell packs with drainage holes, in flats or trays to facilitate watering from below as needed. With a sharp blade or pruning tool, make cuttings 2 to 4 inches long. Each cutting should have 2 or 3 nodes. A node is where leaves attach to the stem.
Cut between, rather than at the nodes. Plunge the proximal end (closest to the roots on the mother plant) of the cutting into the rooting medium far enough so that at least one node is buried and at least one node remains above the surface. Remove all leaves from buried nodes. Above the surface, remove large leaves by cutting or pinching leaf stems, taking care not to damage the tiny axillary leaves emerging behind large leaves.
These axillary leaves are the growing points of your new plant. Keep cuttings at 20 - 25°C. Outdoors, or in a sunlit greenhouse, cuttings should be misted several times per day until roots are well formed. After about a week, growth should be evident if rooting was successful.
After 3 to 4 weeks, transfer plants to larger pots (at least 3-4 inches in diameter) with standard potting soil. Transplant these to the garden in another 2 to 4 weeks or keep as a container plant.
When stems reach 7 to 10 inches in length, cut them back to promote branching and vigor.
The Secret of SteviaRebaudiana
The sweet secret of Stevia lies in a complex molecule called Stevioside which is a glycoside composed of glucose, sophorose and steviol. It is this complex molecule and a number of other related compounds that account for Stevia Reubaudiana's extraordinary sweetness. The Stevia herb in its natural form is approximately 10 to 15 times sweeter than common table sugar. Extracts of Stevia in the form of Steviosides can range anywhere from 100 to 300 times sweeter than table sugar. And best of all, Stevia does not affect blood sugar metabolism according to most experts. Some studies even report that Stevia reduces plasma glucose levels in normal adults.