Stevia - Herb of the Week

Stevia is an herb you hear quite a bit about in the press these days.  This is an herb I never grew much of when I first learned of it because it does have an odd taste that not everyone likes. 

However, with so much information out there, not all of it accurate, I decided that I should focus on this for the Herb of the Week - Stevia (Stevia rebaudiana)

Stevia is a genus of about 240 species of herbs and shrubs in the sunflower family (Asteraceae), native to subtropical and tropical regions from western North America to South America. The species Stevia rebaudiana, commonly known as sweetleaf, candyleaf, sugarleaf, or simply stevia, is widely grown for its sweet leaves. The leaves of the stevia plant have 30–45 times the sweetness of ordinary table sugar. The leaves can be eaten fresh, or put in teas and foods. As a sweetener and sugar substitute, stevia's taste has a slower onset and longer duration than that of sugar, although some of its extracts may have a bitter or licorice-like aftertaste at high concentrations.

With its steviol glycoside extracts having up to 300 times the sweetness of sugar, stevia has attracted attention with the rise in demand for low-carbohydrate, low-sugar sweeteners. Because stevia has a negligible effect on blood glucose it is attractive to people on carbohydrate-controlled diets.

The availability of stevia varies from country to country. In a few countries, it has been available as a sweetener for decades or centuries; for example, it has been widely used for decades as a sweetener in Japan. In some countries health concerns and political controversies have limited its availability; for example, the United States banned stevia in the early 1990s unless labeled as a dietary supplement, but in 2008 it approved rebaudioside A extract (from the S. rebaudiana) as a food additive.

Stevia genus were first researched by Spanish botanist and physician Petrus Jacobus Stevus (Pedro Jaime Esteve 1500–1556), from whose surname originates the Latinized word stevia. Human use of the sweet species S. rebaudiana originated in South America.  The plant was used extensively by the Guarani people for more than 1,500 years, and the plant has a long history of medicinal use in Paraguay and Brazil where the leaves have been traditionally used to sweeten local teas, medicines and as a "sweet treat".

In 1899 Swiss botanist Moisés Santiago Bertoni, while researching in eastern Paraguay, first described the plant and the sweet taste in detail. Only limited research was conducted on the topic until, in 1931, two French chemists isolated the glycosides that give stevia its sweet taste. These compounds, stevioside and rebaudioside, are 250–300 times as sweet as sucrose, heat-stable, pH-stable, and not fermentable.

In the early 1970s, sweeteners such as cyclamate and saccharin were suspected of being carcinogens resulting in further cultivation of steviua as an alternative, beginning in Japan. The plant's leaves, the aqueous extract of the leaves, and purified steviosides were developed as sweeteners. Japan currently consumes more stevia than any other country, with stevia accounting for 40% of the sweetener market.

Stevia species are found in the wild in semiarid habitats ranging from grassland to mountain terrain. They do produce seeds, but only a small percentage of them germinate.  Cultivation from cuttings or root division are more effective.

To Grow

If you enjoy gardening, Stevia can be a rewarding herb to grow. While it's not feasible for most of us to grow sugarcane or sorghum in our backyard, several Stevia plants will fit nicely into a small garden. Recipes utilizing Green Stevia Powder are now available, and the whole leaves add to the flavor of herbal teas.

Stevia rebaudiana seeds are rarely available because of production problems and poor germination, so plants are generally used instead. Plants are available from several mail order sources. Be sure you are getting Stevia rebaudiana since this is the only sweet variety. Stevia stems are brittle, but nurseries have developed packing methods to protect them in transit. Arrange for plants to arrive soon after your last frost date.  High temperatures may stress transplants. Transfer plants to the garden as soon as possible after arrival, making sure they don't dry out in the meantime.  Stevia stem cuttings root easily without hormones, but only under long day conditions.

Stevia rebaudiana is a tender perennial, native to semi-humid subtropical regions of Paraguay and Brazil. Wild plants occur on acid soils that are constantly moist, but not inundated, often near the edge of marshes or streams where the soil is sandy. In the garden, too, Stevia doesn't like to dry out, but standing water will encourage rot and disease. Stevia can be a successful garden plant in most climates with the use of a few simple techniques. Raised beds or hills prevent "wet feet," while an organic mulch and frequent watering ensure a constant supply of moisture.

In North America, Stevia survives winters only in the warmest areas such as southern California, Florida, and Mexico. Research in Japan indicates a critical winter soil temperature below 32 F to 35 F will result in the plant’s death . Stevia is a weak perennial, so plants grown as perennials should be replaced every few years. In colder areas, like ours here in Illinois, Stevia is planted after the last frost and treated as an annual. Longer summer days found at higher latitudes favor leaf yield and Stevioside content, since we are not much above sea level here in the Midwest, I have never been able to test this theory.

While tolerant of most soil types, Stevia prefers a sandy loam or loam. Any well-drained soil that produces a good crop of vegetables should work fine. Stevia occurs naturally on soils of pH 4 to 5, but thrives with soil pH as high as 7.5. However, Stevia does not tolerate saline soils. Unless your soil is very sandy, raised beds are ideal for Stevia. A raised growing surface prevents standing water and reduces compaction. Beds should be 3 to 4 feet wide and 4 to 6 inches high.

In garden beds, space plants 10 to 12 inches apart in the row, with two rows per bed. Stagger rows so that plants end up in a zigzag pattern. Use a trowel to dig a hole, then pour in some water and set the plants a bit deeper than they were in the pot, so the root ball is covered by a thin layer of garden soil. After back-filling around the roots, water again to settle the soil. If the weather is hot and sunny at planting time, it's a good idea to place a thin mulch around the plants to reduce moisture loss. Cool night temperatures will halt plant growth. For early plantings or areas with cool summers, hotcaps or row covers will allow faster growth and offer protection from late frosts. Don't let the plants overheat on hot days, however.

While a good compost usually satisfies nutrient requirements, soil testing or plant symptoms may alert you to deficiencies. Mark Langan of Mulberry Creek Herb Farm recommends low nitrogen or organic fertilizers. Excess nitrogen promotes rank growth with poor flavor.  When I found out that Stevia prefers the “hill” method I use in my production garden, I was off and running to grow some, especially when I had to replace a number of perennials this year die to the flood damage.  To grow in hills, set plants in low mound of dirt spaced 12 to 18 inches apart. Periodically during the growing season, pull more soil up around the plants with a hoe. This tends to smother weeds and drain away surface water which in turn discourages disease.

In general, Stevia should be treated as a vegetable crop. Where summers are extremely hot, stevia benefits from slight afternoon shade. Elsewhere, grow stevia in full sun.  When hot weather sets in, usually a month after planting, beds should be mulched 3 to 6 inches deep with organic residue such as grass clippings, chopped leaves, straw, hay, or compost. This will protect the shallow feeder roots and hold in moisture. Plant growth is slow at first, accelerating by mid summer. Stevia stems are prone to breakage during high winds. Left unpruned, stevia will grow into a lanky, upright plant that produces tiny white flowers in late summer. To maximize leaf production, you must trim back the plants several times to induce branching, first when plants are about 8 inches tall, and again in early summer. So pinching tips out every 3 to 4 weeks for the first month to encourage side branching will give you a bushier plant less prone to damage. (see my post on pinching for more details) 

Grow in a protected area if possible. Supporting the plants with a "corral" made from strings tied to stakes is another strategy.  I am considering making a willow fence to place along the top of the hill they growing for added protection.

Willow windbreak

williwIf you live in Zone 8 or warmer, stevia is often winter-hardy and grows as a short-lived perennial with a protective winter mulch. In colder climates, prepare two healthy parent plants for overwintering indoors. Choose 1-year-old plants grown from seeds or cuttings. Cut them back to about 6 inches, and prune roots as necessary to settle them into 6-inch containers with a light-textured potting mix. Move your stevia plants to a warm, sunny location indoors, or to a heated greenhouse. In spring, when new growth appears, cut most of the new stems and root them in moist seed-starting mix.

To Use

For centuries the Guaraní peoples of Paraguay used stevia, which they called ka'a he'ê ("sweet herb"), as a sweetener in yerba mate and other foods, and medicinally as a cardiac stimulant, for obesity, hypertension and heartburn, and to help lower uric acid levels. Current research has evaluated its effects on obesity  and hypertension. Stevia has a negligible effect on blood glucose, and may even enhance glucose tolerance; it may be useful as a natural sweetener for diabetics.

Use fresh leaves for tea or eat a few right off the plant. They taste great with mint leaves. Sweetness is greatest just before flowering, which is triggered by short day lengths. The onset of blossoming ranges from mid summer to late fall. Plants should be harvested before the first frost or as soon as blossoming begins, whichever comes first. Cut entire plants just above ground level. When growing Stevia as a perennial or for early harvests, clip the plants 6 inches from the ground so they will survive and re-grow. Most herbs should be harvested in the morning, after dew has evaporated, but it is even more important with Stevia as the flavor is at its peak in the morning.

In most areas, you can harvest stevia in midsummer by cutting back the plants by half their size, and again in early fall when new growth slows to a standstill. Stevia can be dried in bunches like other herbs. Plants are easily dried by hanging upside down in a dry, warm, drafty location. Bunch a few plants together and bind at the stem end with a rubber band. Store dried stevia leaves in an airtight container in a cool, dark place. Wait until you’re ready to use stevia leaves to crush them. They keep well for years. Stems are less sweet, so toss them on the compost pile. An alternative method is to strip fresh leaves from stems and spread on elevated screens in the sunshine, on a day with low relative humidity (less than 60%). If drying takes 8 hours or less, very little Stevioside will be lost. A food dehydrator on low heat (100 F to 110 F) will do an excellent job as well. Leaves are crisp, crumbly, and bright green when fully dry.

While whole leaves are great for making tea, it's easy to turn them into Green Stevia Powder with a kitchen blender, food processor, or coffee grinder with metal blades. With the blender bowl half full, process dry leaves at high speed for a few seconds. Collect the fine powder for use in recipes calling for Green Stevia Powder. Use a clean glass jar for long-term storage.

You can use the leaves of this healthy sugar substitute fresh or dried, but many people find the flavor improves if the sweet compounds have first been extracted in water or alcohol. With stevia, slightly under-sweetening drinks or fruit desserts tends to taste better than using too much. Too much stevia may impart a bitter or medicinal flavor.

Why Grow it if you can buy it?

 

Many commercial drink mixes and packaged sugar substitutes are sweetened with a derivative of stevia. This sweetening compound is called Rebaudioside A and is listed on labels as either Reb A or Rebiana. These are highly processed products developed by large food corporations. Most of the raw stevia used to produce these products is grown in China. These “natural sweeteners” have been stripped of many of the plant’s healthful properties. Teas, extracts and tinctures made from high-quality, whole-leaf stevia that you grow yourself or obtain from a farmer’s market, on the other hand, contain up to seven sweet compounds (glycosides) and an array of antioxidants.

 

RECIPES

When first starting to use stevia as a healthy sugar substitute, start with a little and increase the amount gradually and only in small increments. Take care not to overheat stevia teas or extracts. Such batches may be bitter.

Barbara Pleasant created a Stevia-to-Sugar Equivalent Chart for the February/March 2013 issue of Mother Earth Living that is worth checking out.

Making Sweetners –

Stevia Green Powder. Using a food processor or blender with metal blades, fill the blender bowl half full with crisp green dry leaves.  Process dry leaves at high speed for a few seconds until you get a powder that resembles rubbed sage. Use this in any recipe that called for powdered stevia or stevia liquid.

Stevia Tea. Fill a metal tea ball with 1 rounded tablespoon of dried, lightly crushed stevia leaves. Place in a clean pint canning jar, and cover with almost-boiling water. Steep 10 minutes before removing the stevia. Screw on the lid and keep in the refrigerator for up to 5 days. Yield: 2 cups (16 ounces), sweetness equivalent to about 2 cups sugar.   I like to use this because the sweetness equivalent is the same as sugar in a recipe making it easy to substitute.

Stevia Extract. Bring 1 cup water to almost-boiling, add one-half cup lightly crushed stevia leaves. Remove from heat, cover with lid, and steep 40 minutes. Strain through a coffee filter, and pour into a dark-colored container. Store in the refrigerator 1 to 2 weeks. Yield: 3/4 cup (6 ounces), equivalent to 3 cups sugar.  This is concentrated so use 1/3 what a recipe would call for in regular sugar.

Stevia Tincture. Place one-half cup dried, lightly crushed stevia leaves in a clean glass jar. Add 3/4 cup 100-proof vodka or rum. Screw on the lid and shake. Place in a cool, dark place for two days, shaking the jar twice a day. Strain through cheesecloth or a jelly bag, and place the liquid in a small saucepan. Heat on low until steam rises, and maintain that temperature for 20 to 30 minutes, (do not boil). This creates a more concentrated tincture while removing most of the alcohol’s taste and smell. Pour the cooled tincture into a dark-colored container. Store in the refrigerator up to 3 months. Yield: About 1/4 cup (2 ounces), equivalent to 6 cups sugar.   This is heavily concentrated so a teaspoon would equal a ½ cup of sugar.  If you use in a recipe you must replace the missing bulk of the ½ cup of volume.  You may just want ot use this for small sweetening jobs.  Store stevia tincture in a medicine bottle with a dropper to add it to drinks or prepared dishes by the drop.

Crisscross Peanut Butter Cookies

1/4 cup butter or margarine, softened
2/3 cup natural peanut butter
1/4 teaspoon powdered or clear liquid stevia extract 
2 tablespoons date sugar (optional)
1/2 teaspoon maple flavoring
1/4 cup apple butter
1 large egg
3/4 cup whole wheat pastry flour
1/2 teaspoon baking soda
1/2 teaspoon cinnamon
1/8 teaspoon salt
Preheat the oven to 350°F. Oil a cookie sheet. Soften and cream the butter or margarine in a mixing bowl. Cream the peanut butter into the butter. Mix in the stevia extract, date sugar, maple flavoring, and apple butter. Beat in the egg until thick and smooth.  Stir the flour, baking soda, cinnamon, and salt together in a bowl. Add the flour mixture to the peanut butter mixture.  Place large balls of batter on the cookie sheet using two spoons. Flatten each cookie with a floured fork, making a crisscross pattern.  Bake at 350 degrees for 12 minutes. Makes 16 large cookies or 24 smaller cookies.

Vegan Peanut Butter Cookies
1/4 cup oil
2/3 cup peanut butter
1/3 cup apple butter
2 ounces tofu (mix the tofu with the apple butter in a blender first)
1/2 teaspoon stevia extract 
2 tablespoons date sugar (optional)
1/2 teaspoon maple flavoring
3/4 cup whole wheat pastry flour
1/2 teaspoon baking soda
1/2 teaspoon cinnamon
1/8 teaspoon salt
Preheat the oven to 350°F. Oil a cookie sheet. Soften and cream the oil, apple and peanut butters and tofu together in a mixing bowl.  Mix in the stevia extract, date sugar, maple flavoring until thick and smooth.  Stir the flour, baking soda, cinnamon, and salt together in a bowl. Add the flour mixture to the peanut butter mixture.  Place large balls of batter on the cookie sheet using two spoons. Flatten each cookie with a floured fork, making a crisscross pattern.  Bake at 350 degrees for 12 minutes. Makes 16 large cookies or 24 smaller cookies.

Apple Crisp Recipe

 

Filling: 
7 to 8 cups chopped apples (peeling is optional)
3 tablespoons lemon juice or apple cider vinegar
1 teaspoon vanilla
1 to 1 1/2 teaspoons powdered stevia leaf or 1/2 teaspoon powdered or clear liquid stevia extract 
2 tablespoons whole wheat flour
3 tablespoons natural peanut butter (optional)
1 teaspoon cinnamon
1/4 teaspoon salt
2/3 cup apple juice or blend

Topping:  
1 cup rolled oats
2/3 cup chopped nuts and seeds
1/4 teaspoon powdered or clear liquid stevia extract (See “How to Make Stevia Extract” toward the end of this article.)
3/4 teaspoon stevia concentrate 
2 tablespoons oil

Preheat the oven to 350°F. Butter a large, 9 x 13-inch baking dish. Place the apples in a large mixing bowl. Stir in the lemon juice. Mix the vanilla, stevia leaf or stevia extract, flour, peanut butter, cinnamon, and salt into the apples. Pour the fruit juice into the bottom of the dish. Spoon in the apple mixture.  Mix the oats, chopped nuts and seeds, stevia extract, and stevia concentrate together in a bowl. Sprinkle and stir in the oil. Spread the topping over the apples so it is evenly distributed.  Bake for 50 minutes to l hour. If the topping gets done before the apples, cover pan with foil the last 15 minutes of baking.  Serves 8.
Option: Use about 1 1/2 cups granola for the topping. Mix 1/2 cup of the granola into the apples, and spread the rest on the top. No need to add the stevia extract, stevia concentrate, and oil from topping recipe above—granola already has sweetener and oil.