Stevia rebaudiana, the plant behind the popular sweetener
Last week, I was vacationing in Canada when an interesting commercial popped up on the television. It was an ad for the sweetener, stevia, and it featured enthusiastic users growing plants at home. Needless to say, it caught my attention. I had heard that stevia was derived from a ‘natural’ source. But I’d never stopped to consider what that meant from a gardening perspective.
I decided to dig deeper.
STEVIA HAS BEEN AROUND FOR A LONG, LONG TIME
These days, stevia is perhaps best known as an alternative to sugar. But in the botanical world, it is a genus of about 240 species of herbs and shrubs from the sunflower family, Asteraceae. Among the species, only one exhibits the highest level of sweetness; Stevia rebaudiana. Native to Paraguay and Brazil, the herb has been used for centuries to sweeten tea and food as well as to treat various ailments and diseases.
A stevia plantation in Indonesia/Photo: shutterstock.com
We have the Paraguayan chemist Ovidio Rebaudi to thank for identifying what makes Stevia rebaudiana so sweet. In 1900, he began studying the plant to determine its constituents. He discovered that stevia rebaudiana’s leaves were packed with compounds called steviol glycosides. And, when extracted and refined, these compounds were 200 times sweeter than processed sugar.
In fact, it took only a small amount of stevia to produce the same level of sweetness as sucrose. And since humans were unable to metabolize steviol glycosides, the extract was not only calorie-free, but also didn’t raise blood sugar levels when digested.
It’s no wonder the world was jumping on the bandwagon.
IT’S NATURAL, BUT IS IT NATURAL?
Powder and dried leaves of fresh stevia
According to the latest report by IMARC Group, the global stevia market reached a value of more than USD 490 million in 2018 and is projected to reach nearly USD 818 million by 2024. Stevia currently represents an almost 40% share of the total global sugar substitutes market. However, it also has its share of detractors.
Take, for instance, the way in which it’s processed. This is what the website stevia.com says about its processing:
To extract the plant’s sweetness, stevia leaves are harvested, dried and steeped in hot water. They then undergo multiple stages of filtering and centrifuging to concentrate the sweetest components of the leaf. The result is purified stevia leaf extract, ready to be sold commercially.
IMARC Global Stevia Market Report
Online, however, there is much disagreement about stevia’s suitability for food. A deeper dive reveals that although stevia leaf extract comes from a natural source (the plant), its leaves are generally processed in a lab with hot water as well as with the chemical compound, ethanol.
Adding to the confusion is that the FDA considers the highly purified form of the plant’s leaves to be Generally Recognized As Safe (GRAS) – (that is, the steviol glycsoides found in the leaves). But to date, it has not approved whole stevia leaves and crude (non-purified) stevia extracts for use in food due to the lack of generally accepted specifications.
Maybe the herb is best grown and processed at home.
HOW TO GROW AND HARVEST YOUR OWN STEVIA
Ready to follow the people in the ad and grow your own stevia? The sun-loving perennial is listed as hardy to USDA Plant Hardiness Zones 11 and up. Like most tropical species, it thrives in hot climates and will die back in a freeze. However, in most areas of the country it can be grown successfully as an annual.
Leaves of stevia rebaudiana
In fact, according to Park Seed (one of the oldest seed companies on line), stevia rebaudiana takes well to containers. They recommend planting 3 to 5 plants per pot. Like other herbs, stevia rebaudiana benefits from frequent pruning to prevent lankiness and to encourage branching. Expect it to grow to around 24″ tall.
In early to mid autumn, the herb will produce bunches of tiny, tubular white flowers. But if you’re planning on harvesting fresh leaves, make sure to do so before they’ve opened. Once the flowers blossom, the leaves often adopt a bitter aftertaste.
White flowers of stevia rebaudiana
Stevia growers recommend harvesting fresh leaves in the morning when the plant’s sugar content is highest. You can eat the leaves directly off the plant or dry them and save them in airtight containers. Dried leaves are generally sweeter than fresh ones. And they can be ground in a blender into a granulated powder.
Dried stevia leaves
A note on cold drinks- the leaves must be steeped in hot water to release their sweetness. So use fresh leaves as a sweet, edible garnish instead.