Wednesday, 14 March 2012

Stevia (Stevia rebaudiana)

Stevia (Stevia rebaudiana) is an herbaceous perennial shrub native to Paraguay and Brazil. It is also known as sweet leaf, candy leaf, sugar leaf and sweet herb. Today stevia is mostly grown for the leaves which are used as a sweetener but this plant is also an important medicinal herb.

Stevia (Stevia rebaudiana)

Natural sweetener
The sweetness in stevia is due to a glycoside called stevioside. The amount of stevioside (and therefore the sweetness) varies from plant to plant. The quantity is triggered by short day length and is at its highest immediately prior to flowering.

Stevia is usually sold as an extract (liquid or white powder) or powdered plant leaf (green powder). Beware the extracts as they may be highly processed and contain binders, fillers and additives. The green powder, on the other hand, is more natural since it usually just contains the dried leaf. Stevia is relatively easy to grow and home grown freshly picked stevia leaves are by far the healthiest way to use this plant.

Health benefits
Stevia also has important health benefits and was used for centuries by the Guarani Indians of Paraguay as a sweetener and medicinal plant. More information about this can be found at Raintree's Rainforest Plant Database.

Growing Stevia
Stevia can be grown from cuttings or seed. We grew several batches of stevia from seed last year and the germination rates were erratic and low. We found that starting them off in a heated propagator gives them the best chance. Once plants are a reasonable size they can be potted on. Plants should be grown in a sunny spot in free draining soil. We kept the shallow roots moist by mulching with home made compost and grass cuttings. Once established they can be used to take cuttings. Cuttings should be taken in between nodes and should contain three or four nodes. Be careful with the leaves and stems as they are quite fragile and can be damaged very easily.

Our plants have been raised in the polytunnel to protect them from the frosts, the birds and the slugs. According to some references, stevia is naturally resistant to most pests and one of the last plants that insects feed on. In our experience they are not one of the last plants that birds and slugs feed on!

Overwintering plants
Plants can be overwintered in the British Isles. They should be cut down to about 20cm in height and kept under cover. For optimum conditions the soil should not drop lower than 0°C. This plant is known as a weak perennial and some suggest replacing the plants every few years because they become less productive. Our plants have only come through their first winter with us so we don't know how weak they are! They may become very weak if their leaves are systematically harvested year after year.

Raw edible parts
The leaves, growing tips and young stems are edible raw. Leaves are good in salads. Fresh and dried leaves can be used to make a sweet green tea. We don't have any information about the roots or the flowers of this plant. It seems likely that they are also edible but we can't find any references to this.

nb. the leaves, growing tips and young stems can be cooked and eaten like other leaf vegetables.

Processing stevia leaves
To ensure as much sweetness in the leaves as possible harvest just before flowering. Cut down the branches to about 20cm from the base of the plant and the strip off the leaves and growing tips by hand. Stems are a bit woody and less sweet so can be composted. Dry quickly using a dehydrator at around 40°C until very crispy. If leaves are dried in under 8 hours, very little stevioside (and therefore sweetener) will be lost. Store in airtight containers out of the direct sunlight. The leaves can be ground down to a fine powder just before use.

1 comment:

  1. I'm in touch with a fair number of both UK and US herbalists and I'm not aware of them using stevia medicinally. If you are looking for support for conditions such as diabetes and high blood pressure it is best to consult a qualified herbalist through the NIMH online database and stick to locally grown UK herbs such as goats rue and hawthorn.