Stevia, known botanically as Stevia rebaudiana, is a warm climate perennial herb grown for the use of its leaves as a sweetening agent. According to Washington State University, stevia leaves are up to 300 times sweeter than table sugar and carry no calories. Stevia leaves are dried for processing or used fresh. An ancient herb, stevia was once sold in health food stores, but is becoming a more mainstream sweetener. The germination failure rate can be high with stevia seeds so purchase and plant more seeds than you wish for in adult plants to compensate for this, advises Purdue University. The seeds can readily be purchased in small quantities for home use and in bulk for cultivation as a crop.
Buy your stevia seeds from reputable seed dealers, either from mainstream seed catalogs, specialist herb or stevia nurseries, or agricultural supply retailers or wholesalers. Many of these resources are readily available online or seeds can be purchased via mail, phone or fax from a printed catalog.
Look to purchase black or dark brown stevia seed over tan stevia seed as the dark seed has a much higher germination success rate than tan seed, according to Purdue University. The seeds may not be entirely black or brown but you want to avoid clear, pale and tan seeds. Black seed can germinate at a rate of 76 percent while tan stevia seed germinate at a rate of roughly 16 percent.
Be prepared to pay for quality seed and purchase the proper amount for your planting area. Small volumes of seed are purchased by number of seeds in a packet. As of summer 2010 a packet of 15 seeds can be purchased and delivered for less than $10, including shipping. Large volumes of seed are sold by weight in grams or pounds, and as of summer 2010, a 50-gram canister of stevia seed can be purchased at retail for less than $400 including shipping. Each gram contains between 2,800 and 3,000 seeds and the mature plants require 12 to 24 inches of growing space.
Feel the weight of the seed in your hands or by measure when purchasing seed in person. Quality and viable stevia seed with healthy embryos capable of germination will weigh more and feel weightier in your hand than poor quality seed-lacking embryos. You can also cut open a few seeds to check for embryos. A healthy viable seed will have a white center when cut open while a poor quality or non-viable seed will be empty inside or clear in color.