The plant Stevia rebaudiana is widely recognized for its intensely sweet leaves, which contain steviol glycosides used as a natural, zero-calorie sugar substitute. Optimal cultivation relies on creating a balanced micro-environment where the plant can thrive, producing the highest concentration of its sweet compounds. Companion planting is the practice of growing different plant species in proximity for mutual benefit, maximizing garden efficiency and plant health. By carefully selecting companions, a gardener can improve soil quality, manage common pests, and regulate the specific growing conditions needed for high-quality stevia.
Companion Plants for Pest Deterrence
Stevia benefits significantly from aromatic companion plants that confuse or repel common garden pests through strong, masking scents. The primary goal is to disrupt the chemical signals pests use to locate their host plants, essentially hiding the stevia within a blend of powerful odors.
Herbs like basil are particularly effective, as their pungent foliage helps to deter insects such as whiteflies and certain beetles from settling on the stevia leaves. Planting basil approximately 12 to 18 inches away from stevia ensures both plants have adequate space while providing a protective perimeter.
Marigolds are an excellent choice for pest management, specifically those varieties known for their strong scent, which can repel harmful nematodes in the soil and deter general pests above ground. Nasturtiums are effective at drawing aphids away from stevia, acting as a “trap crop,” while also attracting beneficial insects like ladybugs that prey on aphids. Other fragrant herbs such as thyme and rosemary release volatile organic compounds that contribute to the overall pest-deterring aroma of the garden space.
Companion Plants for Soil Enrichment and Growth
Stevia is a shallow-rooted plant that performs best in fertile, well-draining soil with consistent moisture and requires a significant amount of nitrogen for optimal leaf production and sweetness. Companion plants can directly improve the physical and chemical properties of the soil to support this need.
Nitrogen Fixation
Legumes such as clover, vetch, or cow-pea are excellent for enriching the soil through biological nitrogen fixation. These plants form a symbiotic relationship with rhizobia bacteria, which convert atmospheric nitrogen into a form usable by plants. This nitrogen is eventually released into the soil when the legume biomass decomposes.
Moisture and Shade Management
Low-growing ground covers are valuable for maintaining the necessary microclimate around the stevia plant’s shallow root system, which is susceptible to drying out. Creeping thyme and sedum are suitable choices because they share stevia’s preference for sunny, well-drained conditions. These dense, mat-forming plants help to suppress competing weeds and reduce soil temperature fluctuations, conserving moisture by shading the soil surface. Taller companions, such as sunflowers or tomatoes, can also be incorporated to provide necessary partial shade during the most intense heat of the day, which prevents leaf scorch and ensures the stevia remains productive.
Plants That Should Not Be Paired With Stevia (Antagonistic)
Certain plants should be kept at a distance from stevia due to chemical antagonism or intense competition for limited resources. Stevia is not a heavy feeder, and it struggles when planted near species that aggressively deplete soil nutrients and moisture.
Large, nutrient-demanding vegetables like corn and squash are poor companions because they have extensive root systems that fiercely compete for the same resources, effectively starving the stevia plant. A minimum distance of 24 to 36 inches is suggested to mitigate this competitive interaction.
Another consideration is allelopathy, a phenomenon where one plant releases biochemicals that inhibit the growth of others. It is the general garden allelopaths that pose the greatest threat. The black walnut tree, for example, produces the chemical juglone, which is toxic to many garden plants and will severely stunt or kill stevia if planted nearby. Avoiding such antagonistic pairings and ensuring adequate spacing is necessary to prevent growth inhibition and maintain the health of the stevia crop.