Growing Stevia: Nature’s Sweetener

Zero calories, and far sweeter than sugar, the leaves of the Stevia plant offer an alternative to traditional sweeteners in foods and beverages. Unlike chemical sweeteners (Sweet N Low, Nutrisweet, etc) when used right there is no unpleasant aftertaste. A tiny bit goes a long way. Just one half teaspoon of 100% pure stevia extract powder equals the sweetness level of a whole cup of granulated sugar. Yes, you can buy the extract powder, but very few brands are great, and most have other ingredients that come from corn that is likely a GMO product. And then there’s the fact that much of the stevia extracts you can buy in the U.S. are imported from China. Hmm… If you grow your own stevia, you know where it came from, that it is pure, and can also make your own extract.

The sweet compounds in stevia are concentrated in the leaves, and are known as steviocide, a glycoside. There over 150 different kinds of stevia plants that are native to regions of South America where its been used for sweetening food for over 1500 years. The ‘sweet leaf’ cultivar used worldwide as a sugar replacement is Stevia rebaudiana (Bertoni) that’s indigenous to Paraguay. It’s a small tender perennial shrub reaching 2-3′ tall, and is hardy to zone 9. It’s grown as an annual in colder climates, but can also be grown indoors during the cold seasons. You can grow it in the outdoor garden, containers, and in aeroponic or hydroponic systems. The plant loses vigor at 2 years old, so plan on replacing them regularly if you can provide the environment they will thrive in year around.

Some people say that the plant dies after flowering, but this isn’t true. Chances are that the plant was not cared for properly, causing it’s demise after expending so much energy. And like many herbs, the flavor of the leaves is altered once it starts setting bloom. Plus the best tasting leaves are the older ones – so you don’t want it to even think about flowering. Not if you want a great tasting natural sweetener, because flower set turns them bitter. So it’s best to harvest when you first see signs of flower budding in late August to early September outdoors. And pinching the younger plants back will make it grow bushier… which means a more leaves to harvest per plant.

Starting Stevia Plants

This herbal sweetener is notorious for poor germination rates – as low as 50%, or less. Because of this trait most commercial growers plant rooted cuttings to ensure a good harvest. If you start with cuttings – be sure the mother plant is super healthy, and free of pests and disease. Its safer to start your own seeds – just plan ahead for non-performers and seed twice as many cells or rockwool cubes than you need.

The seedlings are super tiny at germination. Even a misting to remoisten your media will wash them under, so use wicking with bottom watering and a humidity dome. You can use HO T5 lights for germination and the first couple of weeks as seedlings, or a SUNNY windowsill.

Not Heavy Feeders

Stevia doesn’t like much nitrogen, so standard garden fertilizers with a balanced analysis is all wrong for them. They do better with bloom formula nutrients – no matter how you’re growing it. In it’s native realm, this plant grows on the outskirts of waterways where a lot of natural nitrogen washes down the slope, and the soil is consistently moist, but never soggy. They have shallow root systems, and have adapted well to low nitrogen and high potassium. Some backyard gardeners report that they just stick stevia in the ground and keep it watered with excellent results, but it would depend on your particular soil makeup. In potting mix or hydroton you’ll have to supply the right nutrition sources for strong, healthy plant growth.

Obviously, if you’re going to grow stevia hydroponically, you won’t be able to add it to the herb garden system. Best plan on giving it’s own system, or grow one plant in a Dutch bucket.

Best Environment

This plant performs best in temperature range from 59-78°F with medium humidity. However, they grow larger in the warmer end of that range. Outdoors you can’t control the thermometer, but in the indoor garden you can. If you’re where summers are cool, your plants will be much smaller than where temps are higher.

They grow well in hydroton, though may be slow to take off after moving them to your hydroponic system, but that will change when the roots reach the nutrients – at which point, they will probably outperform container-grown specimens (see the difference on Tomorrow’s Garden). If growing in traditional containers, use a light weight potting mix, and mulch the top to protect those shallow roots from drying out.

Light Exposure for Stevia

In much of North America best results are in full sun, though the sun intensity along the southern tier of states might mean that part shade is better. And in colder climates starting your plants in pots that can be sunk into the soil for the warm months and brought indoors for over wintering is a great idea, though once again – be sure the plant is free of pests and disease before bringing it inside. And when you do, the best plan of action is to let it adjust slowly to the difference in light. Bring it in the house for a couple hours a day and gradually increase the time inside to guard against it going into decline.

Prepare to replace full sun and long days when growing it indoors, or your plants will not perform as expected. A 12-hour daylight period is a sure way to make them bolt into bloom. Growing an optimum crop of leaves requires 15-16 hours of grow lights. If you’re growing them indoors in a window over winter, it’s best to provide the hours of sun they’ll be missing with lights. The cloudier your skies, the more list assistance these plants will need. They perform better under full spectrum lamps than cool blue light like other vegetative crops. And remember that full sun is lots of light energy, so don’t try growing it under LEDs, or weak fluorescent lights.

Those with experience growing stevia regularly indoors suggest MH or HPS lights positioned 12″ above the upper leaves… raise your light as the plants grow taller.

The Harvest

When grown year around you can harvest stevia up to 5 times a year. It will grow new stems from where you’ve cut it back. It’s best not to shear it back beyond half of the stem height. When growing stevia outdoors, you can harvest at least two times in a season – midsummer, and early autumn. For those living in 7a or warmer, you might even get a third harvest, since the growing season is so much longer than farther North.

You can use the leaves fresh, but the flavor is not all there yet. As with many herbs, drying intensifies its culinary properties. Some say that air drying is best, while others prefer the taste when curing in a dehydrator. And crushing releases the most sweetness – so whether you’re using the crushed or powderized leaves, or steeping your own stevia extract – don’t use whole leaves. Store your dried harvest in an air tight container. Note that homemade stevia extract will always be liquid. A few drops is all you need to replace teaspoons of sugar.

How Much To Grow

Growing 3-5 plants over the summer will supply you with a family with a year’s supply of home grown natural sweetener. Learning to cook with stevia extract is challenging, but it can totally replace sugar if you’re diabetic.

Its great in coffee and tea. I quit using sugar in my coffee years ago. I like it better with stevia. Try steeping water in the refrigerator with a few fresh stevia leaves and some mint or lemon balm for 2-3 days. A delicious ice cold flavored water for hot summer days. Experiment – there are probably a number of things in your herb garden that will jazz up a glass of cold water that’s stevia sweet.