Stevia rebaudiana Seeds | Stevia
LATIN NAME: Stevia rebaudiana
COMMON NAME: Stevia
Plant Profile
The Guarani people of the Paraguay region used the leaves as a sweetener long before outsiders knew it, calling the plant a sweet herb of the fields. The botanist Bertoni described it in writing at the close of the nineteenth century, and that published account carried the species into cultivation beyond South America. Field collections from the Paraguay uplands remain the source of wild genetic diversity used in breeding.
Dried leaves sweeten herbal tea, and the green powder is stirred into drinks and baked goods where a sugar substitute is wanted. The taste pairs with sharp fruit such as lemon and berry, which masks the faint liquorice note, and it stands up in a slow-cooked compote. Because the glycosides are heat stable, the sweetness survives baking that would destroy a sugar substitute.
Cut the stems at full leaf, dry them out of direct sun, and crumble the leaf for storage; a spoon of dried leaf in a pot of tea is plenty. Mix the sweet leaf with anise hyssop or Korean mint for a fragrant tisane, and lean on chrysanthemum for a floral cup. The blend of sweet leaf and citrus herb is the classic South American preparation.
For cooking, crumble a little dried leaf into a sponge cake batter or a lemon drizzle where a sugar substitute is wanted, since the glycosides hold their sweetness through the oven. A syrup made by steeping the leaf in warm water and straining gives a pour-able sweetener for yoghurt and porridge, and a few leaves dropped into a jar of apple cider vinegar make a fragrant, sugar-free shrub. Because the taste is strong, start with less than you think and adjust, and keep the dried leaf in a sealed jar away from light so the sweet compounds do not fade.
Science & Biotechnology
The plant is an erect, branching perennial with opposite, lance-shaped, finely toothed leaves and small white tubular flowers carried in loose terminal clusters. The leaves are the crop; the flowers are modest and are often pinched to keep the plant leafy and low. Fine glandular hairs on the leaf surface store the sweet compounds, which is why a whole dried leaf, not an extract, can sweeten a drink.
Two named compounds do the work: stevioside gives the strong, slightly liquorice aftertaste, while rebaudioside A is cleaner and less bitter and is the fraction breeders chase. The leaf stores these diterpene glycosides in the epidermal cells, which is why a whole dried leaf sweetens a pot of tea. A third compound, rebaudioside C, appears in young leaf and fades as the leaf matures.
Modern lines are selected for a high rebaudioside A share and a low bitter tail, because the cleaner taste sells. Breeding combines leaf trials with taste panels, and tissue-cultured clones fix a winning line so every plant in a field tastes the same. Work on the stevia genome and the enzymes that build the glycosides lets breeders screen leaf tissue rather than wait for the field.
Uses & Benefits
A single leaf of Stevia rebaudiana tastes many times sweeter than table sugar yet carries no usable calories, because the sweetness comes from steviol glycosides that the human body does not break down for energy. That trick is the reason the plant travelled from a Paraguayan grassland to fields across Asia and to supermarket shelves, and why a small patch of leaves can replace a bag of sugar in the kitchen garden. The taste is clean in the best lines and needs only a little dried leaf to sweeten a whole pot.
Growing from Seed
Shoot-tip culture on a standard medium gives uniform stevia planting stock and multiplies a superior clone far faster than seed, which varies in sweetness. The cloned rows also flower and leaf on the same schedule, easing the harvest, and a single elite mother plant can supply a whole season of field transplants.
In cold climates grow stevia as a summer pot and lift it indoors before frost, because the plant will not survive a hard freeze. Pinch the tips to keep it from flowering too early and to hold a dense, leafy bush, and give a balanced feed through the warm months to keep the leaf tender.
Sow the fine seed on the surface of a light mix and press it in without covering, since light aids the seedling; keep it warm and moist. Pot on when the plants show six true leaves or stand about ten centimetres, and harden them off in light shade before full sun. Whitefly and leaf spot are the usual troubles, kept down by air flow and clean watering.
Our Take
I dry a jar of stevia leaf every summer and it outlasts the season in tea; the rebaudioside-rich clones taste cleanest. For a sweet-herb shelf grow anise hyssop, Korean mint and chrysanthemum alongside it.
Related Reading
Gardeners who grow Stevia often pair it with these related subjects: