Stevia: A Complete Growing Guide

Stevia is a perennial herb grown primarily for its sweet leaves. The species of commercial importance is Stevia rebaudiana Bertoni, a member of the Asteraceae family native to Paraguay and neighbouring parts of South America. Its leaves contain steviol glycosides, particularly stevioside and rebaudioside compounds, which provide the characteristic sweetness and are used in food and beverage products as high-intensity sweeteners.

Stevia has attracted interest among Kenyan farmers as a specialty crop because it can be harvested repeatedly and supplied either as dried leaves or as raw material for further processing. However, it should not be treated as an automatic high-profit crop. The quality of planting material, local growing conditions, harvest timing, drying quality and, most importantly, access to a buyer all determine whether production makes commercial sense.

Understanding Stevia as a Crop

Unlike sugarcane, stevia does not produce sugar that is extracted from a large biomass crop. The commercially valuable compounds are concentrated in the leaves.

The plant is a multi-stemmed perennial herb that can be managed for repeated leaf production. Its agronomic behaviour is strongly influenced by temperature, day length, planting density, nutrition and harvesting regime. Research has shown that these factors can affect both leaf biomass and the concentration and yield of steviol glycosides.

This distinction is important for farmers. A crop producing a large amount of leaf biomass is not necessarily producing the highest-value crop if the leaves have poor quality or an unsuitable steviol glycoside profile for the intended processor.

Is Stevia Suitable for Growing in Kenya?

Stevia can grow in tropical and subtropical environments, but site selection remains important. FAO’s Ecocrop database gives an optimal temperature range of approximately 18–30°C, annual rainfall of about 1,000–1,400 mm, and a preferred soil pH of approximately 5.0–6.5. It also indicates that stevia can be grown in tropical areas at elevations up to about 1,500 metres, although actual performance depends on local conditions and management.

Kenyan experience reported by local agricultural publications indicates that stevia has been grown in areas including parts of the Rift Valley, Western Kenya and Central Kenya. These reports should be treated as evidence that the crop can be grown in those areas, rather than as proof that every farm within a county is suitable.

Before establishing a commercial field, assess the actual farm’s temperature, drainage, soil, water supply and access to markets.

Climate Requirements for Stevia

Stevia performs best where there is sufficient warmth for vegetative growth without prolonged extreme heat. It also requires adequate moisture because leaf production is the primary objective.

FAO data indicate that the crop can tolerate a broader range of conditions than its optimum range, but commercial farmers should not confuse survival with optimum production.

In Kenya, irrigation can be valuable where rainfall is unreliable. However, irrigation should complement suitable site selection rather than compensate for a fundamentally unsuitable environment.

The crop is also sensitive to day length. Shorter days can promote flowering, while longer days favour vegetative growth and higher steviol glycoside accumulation in the leaves.

This makes harvest timing particularly important.

Soil Requirements

Stevia performs best in a well-drained soil that can supply moisture without remaining saturated. FAO lists light to medium-textured soils as suitable and identifies good drainage as an important characteristic.

A soil test should be conducted before commercial establishment. It should provide information about pH and nutrient status and help determine whether amendments are required.

Avoid planting stevia in fields that remain waterlogged after heavy rainfall. Poor drainage can restrict root development and create conditions favourable to root diseases.

Where soils are heavy, raised beds and improved drainage can help, but they should not be viewed as a substitute for proper site selection.

Propagation of Stevia

Stevia can be propagated from seed or vegetatively through cuttings. Commercial production often favours vegetative propagation because it can provide more uniform plants.

Seed propagation can present challenges because seed quality and viability can vary. Vegetative propagation also allows farmers to multiply plants from selected mother plants with desirable characteristics.

For commercial production, planting material should be correctly identified as Stevia rebaudiana and sourced from a reliable nursery or propagation programme. This is particularly important because farmers are not simply buying a generic “sweet herb”. Genetic differences can influence plant growth and the concentration of individual steviol glycosides.

Research has also investigated stem cuttings as a practical propagation method for stevia.

Nursery Establishment

Where seedlings are raised before field planting, use a clean nursery medium with good drainage.

Seeds should be sown shallowly because very small seeds can struggle to emerge if buried too deeply. Maintain consistent moisture without saturating the nursery medium.

The nursery should receive adequate light while young plants are protected from severe environmental stress. Seedlings should be transplanted once they have developed a healthy root system and are strong enough to withstand field conditions.

For commercial farmers, uniformity at transplanting is important because uneven plant establishment eventually produces uneven harvesting and makes labour planning more difficult.

Land Preparation

Prepare the field thoroughly before transplanting.

Remove perennial weeds and break up compacted areas. Where soil tests indicate low fertility or low organic matter, incorporate suitable well-decomposed organic material before planting.

The field should have good drainage and a reasonably level surface if irrigation is to be used.

Raised beds can be particularly useful in areas where heavy rainfall creates temporary waterlogging.

Stevia Spacing and Plant Population

Spacing should be selected according to cultivar, climate, soil fertility, harvesting system and intended production method. There is no single spacing that should automatically be applied to every Kenyan farm.

Research has demonstrated that plant population can significantly affect biomass production and steviol glycoside yield. One field study found that a stand of about 10 plants per square metre performed better than lower densities under the conditions tested. However, this result came from a specific production environment and should not be presented as a universal Kenyan recommendation.

A farmer can begin trials around 40–50 cm between rows and 20–30 cm between plants, then evaluate canopy development, disease pressure, labour requirements and leaf yield.

At 45 cm × 20 cm, the theoretical population is approximately:

4,046.86 ÷ (0.45 × 0.20) = 44,965 plants per acre

This is a theoretical plant population before accounting for paths, missing plants and establishment losses.

Higher density can increase production per unit area, but it also increases the quantity of planting material required and may create a denser canopy. The objective should therefore be an economically optimum population, not simply the highest possible number of plants.

Water Management

Stevia needs adequate moisture for continuous leaf production. It is particularly important to avoid severe moisture stress during establishment and after harvesting.

Where rainfall is insufficient, drip irrigation can help maintain more consistent soil moisture. Irrigation should be adjusted according to soil type, weather and crop development rather than following a fixed schedule regardless of conditions.

At the same time, excessive irrigation is undesirable. The root zone should remain adequately moist but not permanently saturated.

Mulching can help reduce evaporation and suppress weeds, particularly during dry periods.

Fertiliser and Nutrient Management

Stevia has a relatively substantial vegetative component because the leaves are the harvested product. Nutrient management should therefore support sustained foliage production without encouraging excessively soft or unbalanced growth.

Begin with a soil test rather than copying a fertiliser programme from another country.

Nitrogen is important for leaf and shoot development, while phosphorus and potassium contribute to broader plant growth and physiological functions. However, excessive nitrogen is not automatically beneficial. Nutrient requirements also change with soil fertility, crop age, harvesting intensity and expected biomass production.

Organic matter can improve soil structure and moisture management, particularly in soils with poor physical condition.

For established perennial fields, nutrients removed in repeated harvests need to be considered in the fertiliser programme. A farmer harvesting several times each year should not assume that the original pre-planting fertility will remain sufficient indefinitely.

Weed Management

Weeds compete with stevia for water, nutrients and light, particularly during establishment.

Early weed control is therefore important. Hand weeding, shallow cultivation and suitable mulching can all be useful depending on farm size and production system.

Avoid deep cultivation close to established plants because it can damage the root system.

A dense, healthy stevia canopy eventually suppresses some weeds, but farmers should not allow weeds to dominate during the early growth stage.

Pests and Diseases

Stevia can experience insect and disease problems, although the severity varies with production environment.

Farmers should regularly inspect plants for:

• Leaf-feeding insects
• Sap-sucking insects
• Leaf spots
• Stem or shoot problems
• Root and crown rots
• Symptoms associated with excessive moisture

Good field sanitation, healthy planting material, appropriate spacing and drainage should form the first line of defence.

Do not automatically spray an insecticide or fungicide simply because another farmer is doing so. Identify the pest or disease first, then select a product that is legally registered for the crop and intended use in Kenya. Follow the label, application rate, pre-harvest interval and other applicable requirements.

Pruning and Maintaining the Crop

Stevia naturally produces multiple shoots, but commercial management can benefit from practices that encourage a productive, well-branched canopy.

Removing or pinching the growing tip at an appropriate stage can encourage branching, increasing the number of harvestable shoots. However, pruning should be timed according to plant establishment and intended harvest rather than performed indiscriminately.

The plant must have sufficient leaf area to establish a strong root system and recover after cutting.

This is particularly important during the first production cycle. Research has shown that harvesting too aggressively in the first year can reduce the plant’s subsequent performance under some perennial production conditions.

When to Harvest Stevia

Harvest timing has a direct relationship with both leaf production and steviol glycoside concentration.

The general recommendation is to harvest before full flowering when the plant has developed substantial leaf biomass. Reviews of stevia cultivation indicate that harvesting shortly before flowering can favour steviol glycoside concentration, although the exact optimum varies with genotype and growing conditions.

FAO’s crop database gives a broad production cycle of approximately 55–270 days and notes that harvesting patterns vary according to the production system.

Some production systems can begin harvesting several months after field establishment, followed by additional harvests as the plants regrow. The exact interval should be determined from actual plant development rather than forcing every crop onto a fixed three-month schedule.

Harvesting Method

Stevia can be harvested by cutting the above-ground shoots while leaving sufficient plant material to regenerate.

Avoid damaging the crown during cutting.

If the crop is being harvested for dried leaves, the material should be transported rapidly to the drying area. Delays under hot and humid conditions can reduce quality.

Drying Stevia Leaves

Post-harvest handling is particularly important because most commercial stevia products begin with dried leaf material.

Leaves should be dried rapidly under clean conditions while protecting them from contamination, rain, soil and excessive heat.

The objective is to reduce moisture sufficiently for safe storage without compromising quality.

A clean solar dryer or suitable controlled drying system can provide more consistent conditions than exposing harvested leaves directly to unpredictable weather.

Once properly dried, leaves should be stored in clean, dry packaging away from moisture, pests and strong odours.

Farmers selling to processors should establish the buyer’s required moisture level, leaf cleanliness, colour and packaging specifications before production.

Stevia Yield Potential

Yield figures for stevia vary considerably because the crop can be harvested under different systems and reported as fresh leaves, dry leaves, individual harvests or annual cumulative production.

FAO’s Ecocrop database gives examples of dried-leaf yields ranging from about 400–500 kg/ha in the first year to 1.5–2 tonnes/ha in subsequent years in one historical production system, with higher yields reported under other conditions. These figures should not be treated as guaranteed Kenyan yields.

Research also demonstrates that harvesting regime, planting density, genotype and environmental conditions can substantially change both biomass and steviol glycoside yield.

For this reason, farmers should record their own fresh and dry leaf yields from each harvest rather than relying exclusively on advertised per-acre figures.

Stevia Production Economics in Kenya

Stevia can potentially provide several harvests from an established field, which is one of its attractions as a perennial crop.

However, profitability depends on more than the biological yield. Major costs can include:

• Planting material
• Land preparation
• Nursery establishment
• Manure and fertiliser
• Irrigation
• Weeding
• Pest and disease management
• Harvest labour
• Drying
• Packaging
• Transport
• Post-harvest losses

The market price must also be based on the actual product being sold. Fresh leaves, dried whole leaves, powder and extracted steviol glycosides are different products and should not be assigned the same price.

Kenyan websites currently publish widely different stevia yield and price estimates. Because these figures are not consistently supported by independently verifiable farm-gate datasets, they should not be presented as guaranteed income.

A better approach is to obtain a written or otherwise verifiable buyer specification and price indication before planting commercially.

Stevia Markets and Value Addition

The main commercial value of stevia comes from its sweet steviol glycosides. The leaves can be sold as dried raw material, while processors can convert them into powders, extracts and other sweetener products.

Potential market channels include:

• Food and beverage processors
• Herbal product companies
• Sweetener manufacturers
• Health-food retailers
• Specialty shops
• Direct consumers
• Aggregators and contract buyers

The most attractive market is not necessarily the buyer offering the highest price per kilogram. Processing requirements, quality specifications, rejection rates, transport distance, payment terms and minimum volumes also affect the farmer’s actual return.

A farmer producing a smaller quantity of consistently clean, properly dried leaves for a reliable processor may have a better business than one producing a larger crop without a confirmed market.

Can Stevia Be Grown Organically?

Stevia can be incorporated into an organic production system, but farmers should not automatically describe the crop or its products as “organic.”

Organic production involves a defined production standard and, where a market requires certified organic status, compliance with the applicable certification requirements.

Farmers considering premium organic markets should establish the certification and traceability requirements before planting.

Common Mistakes in Stevia Farming

One of the biggest mistakes is planting stevia because it is advertised as a high-value crop without first identifying the buyer.

Other problems include using unidentified planting material, establishing the crop in poorly drained soil, excessive nitrogen application, inconsistent irrigation and harvesting too aggressively before plants are properly established.

Farmers should also avoid assuming that all stevia varieties have the same sweetness or processing value. Steviol glycoside composition varies with genetics and growing conditions, and processors may have specific requirements for the raw material.

Another common error is quoting gross revenue as profit. Gross sales do not account for planting material, labour, irrigation, drying, transport, rejected leaves and other production expenses.

A Practical Approach for Kenyan Farmers

For a farmer considering stevia for the first time, a small commercial trial is preferable to immediately planting an entire acre.

Start by identifying the intended buyer and determining whether they purchase fresh leaves, dried leaves or another form. Obtain their quality specifications and expected delivery volumes.

Then test the farm’s soil and water, source correctly identified planting material and establish a manageable trial. Record establishment losses, labour, irrigation requirements, harvest dates, fresh weight, dry weight and selling price.

After one or more harvests, calculate the actual cost per kilogram of saleable dried leaf. This provides a much stronger basis for expansion than generic online profitability estimates.

Final Considerations

Stevia is a specialised perennial crop with potential for Kenyan farmers who can combine suitable growing conditions with a dependable market. Its value comes primarily from steviol glycosides in the leaves, so production should focus not only on biomass but also on harvest timing, leaf quality and the requirements of the intended processor.

Farmers considering commercial production should start with quality planting material, soil and water assessment, appropriate spacing and reliable moisture management. Most importantly, secure the market before committing substantial acreage.

The crop’s repeated harvest potential can make it attractive, but profitability should be established from actual farm records and confirmed buyer prices rather than unsupported per-acre income claims.

Farmers seeking quality planting materials and expert guidance can contact SeedFarm via website: www.seedfarm.co.ke, Call or WhatsApp: +254712075915, or email: info@seedfarm.co.ke.