Stevia (Stevia rebaudiana) is a non-caloric, natural sweetener, originating in Paraguay. Considered a tender, weak perennial, stevia is often grown as an annual in colder climates. Stevia extracts can be up to 300 times sweeter than processed white sugar. The sweetening compounds of stevia leaves, called steviosides, vary greatly in plants grown from seed; therefore, it is recommended that stevia be grown from starter plants for maximum sweetness. Stevia starter plants are available through local nurseries and greenhouses, and through online and mail order plant distributors.
Choose a location that offers full sunlight and the space to plant stevia 12 to 18 inches apart, with at least two feet between rows.
Use a store-bought soil testing kit, according to manufacturer's directions, to test the pH level of the chosen site. Stevia plants require soil with a pH level between 4.0 and 7.5.
Apply equal amounts of organic compost and sand, at a depth of two to three inches, over the planting site. Rock sulfur should be applied, as well, if the pH level needs to be lowered. The Garden Helper recommends using 3.6 ounces of rock sulfur per square yard.
Work the rock sulfur, sand and compost into to the top six inches of soil, using a spade and pitchfork. Finish amendments by raking the soil surface to break up any remaining clumps.
Dig holes deep enough so that the root ball sits just below the soil line, then fill each hole with water.
Place one stevia plant in each hole and then fill it with surrounding soil, making sure to pack soil firmly around the root ball and base of the plant.
Water each plant to set the soil and eliminate any air pockets in the hole, then spread a thin layer of mulch around the base to prevent weeds and retain even moisture levels.
Apply a water-soluble 6-24-24 fertilizer around the circumference of each plant, following manufacturer's recommendations. Make sure that fertilizer does not come in contact with foliage or stems, to avoid burns. A second application should be administered during midsummer, using the same technique.
Apply a four- to six-inch layer of compost, grass clippings or straw around the base of each plant, one month after planting.
Give stevia one inch of water per week. Increase watering to twice per week if your area is experiencing drought conditions.