Stevia rebaudiana aka Stevia

Stevia rebaudiana grows best at daytime temperatures between 18–30°C and tolerates a range of 15–43°C. Young growth is damaged at or below 0°C, and plants cannot survive frost. In nature it experiences an average temperature of around 24°C. In temperate regions it must be overwintered indoors or treated as an annual.

Stevia is native to humid subtropical environments in Brazil and Paraguay, typically receiving 1,000–1,400 mm of rainfall annually. It performs best in warm, moist conditions. In cultivation, moderate ambient humidity is beneficial; the plant is not suited to arid, dry indoor air without supplemental moisture.

NC State Extension recommends fertilizing stevia every 4–6 weeks during the growing season. Missouri Botanical Garden notes it prefers rich, consistently moist soils, suggesting incorporation of organic matter. No specific fertilizer formulation is cited in authoritative sources.

In temperate climates, stevia is started indoors in spring and transplanted outside after the last frost. During the growing season, flower buds should be regularly pinched off to maintain leaf quality and sweetness. Leaves are best harvested in autumn before the first frost. In USDA zones below 10, plants can be cut back and overwintered indoors in containers, or treated as annuals. Mulching around the root zone helps retain soil moisture during hot summers.

Stevia flowers are described as producing no significant fragrance. The leaves themselves have a sweet, slightly liquorice-like flavour but no notable scent is reported by botanical sources.

Stevia rebaudiana produces small, tubular white flowers with light purple accents, borne in terminal clusters typical of the Asteraceae family. Bloom time is July to August. Flowers are generally removed in cultivation to maintain the highest leaf quality and sweetness, as stevioside concentrations decline once flowering begins.

No major cultivated varieties are documented in the authoritative sources consulted. Commercial breeding has selected for higher rebaudioside A content (which has a cleaner sweetness profile than stevioside), but named cultivars are not listed in botanical databases.

Stevia can be grown outdoors year-round in USDA zones 10–11. In cooler climates it is grown as a seasonal herb, planted outside after the last frost in a full-sun to lightly shaded position in moist, well-drained sandy loam. Raised beds improve drainage and help prevent root rot.

Pruning or pinching off flower buds as they appear is the most important maintenance task for stevia. Leaves produced before flowering have the highest stevioside content and best flavour. Regular bud removal extends the productive leaf season. After harvest, stems can be cut back to encourage fresh growth.

Missouri Botanical Garden notes stevia can be overwintered indoors in containers. Because roots are shallow and the plant is relatively small (to about 60 cm), container culture is practical. Standard guidance for container herbs applies: repot when roots fill the pot, using a well-drained sandy loam mix.

No specialist cleaning guidance is documented in authoritative sources. Standard practices for removing dust from leaves with a damp cloth apply. Removing dead or yellowing leaves promptly supports air circulation and reduces disease risk.

Stevia is most reliably propagated via stem cuttings, as seeds have low germination rates and produce variable plants. Cuttings are taken from healthy stems and rooted in moist compost. If growing from seed, sow in spring in a warm greenhouse, barely covering seeds and maintaining moist compost; transplant seedlings after the last frost. Division of the rootstock is also possible.

Yellowing leaves in stevia most commonly result from overwatering or waterlogged soil, which can trigger root rot. Missouri Botanical Garden specifically warns against overwatering. Ensure the growing medium is well-drained and sandy. Insufficient light or nutrient deficiency during the growing season can also cause yellowing.

Brown leaf tips or edges are typically associated with drought stress, heat scorch, or low humidity. Stevia prefers consistently moist (not wet) soil; allowing the medium to dry out excessively causes leaf tip browning. In hot climates, mulching helps maintain root moisture.

Drooping or wilting in stevia is most commonly caused by water stress — either underwatering (dry soil) or overwatering leading to root rot. The plant's stems are naturally somewhat weak and floppy, so some laxness is normal. Ensure adequate moisture and drainage to distinguish structural habit from stress-related wilt.

No specific leaf-drop issues are documented for stevia in authoritative sources. Significant leaf drop may indicate cold damage (temperatures at or below 0°C damage young growth), waterlogging, or the plant entering dormancy. In frost-free zones it remains evergreen.

Stevia seeds have notably low germination rates, which can make early growth appear slow. Once established, growth rate is moderate. Long days promote leaf production and higher stevioside content; short-day conditions trigger flowering rather than vegetative growth. Adequate sun and warmth are the most important factors for vigorous growth.

Missouri Botanical Garden reports no serious insect or disease issues for stevia. The main cultivation risk is root rot from overwatering or poorly drained soils. Standard prevention (well-drained sandy loam, avoiding waterlogging) is sufficient in most cases.

Stevia rebaudiana belongs to the Asteraceae family and produces small composite flowers that are typically insect-pollinated. In cultivation, flowers are usually removed before pollination can occur, as leaf quality declines post-flowering.

Stevia leaves are edible raw or cooked and are prized as a natural, calorie-free sweetener. The primary compound stevioside is approximately 300 times sweeter than sucrose; rebaudioside A is similarly potent with a cleaner flavour. Dried leaves can be ground into powder, steeped in water, or added to herbal teas. The leaves have a sweet, slightly liquorice-like flavour. Steviol glycosides extracted from stevia are GRAS-approved in the US and approved for food use in the EU since 2011. PFAF rates edibility at 4 out of 5.

Stevia has a long history of traditional use among Guaraní peoples for diabetes, hypertension, and as a general tonic. Research has shown that stevioside can lower blood glucose by enhancing insulin secretion, and crude leaf extracts reduce blood pressure and increase sodium excretion. Studies have also explored anti-inflammatory, antibacterial, antioxidant, and anticancer properties of leaf compounds. Kew MPNS notes the plant itself is not explicitly cited in the formal medicinal literature, though related compounds are well-studied. Useful Tropical Plants rates medicinal value at 2 out of 5.

Beyond its well-known use as a sweetener, stevia leaf extract is used as an ingredient in commercial cosmetic preparations as a skin conditioner. Steviol glycosides are commercially extracted for use in food and beverage products globally. Useful Tropical Plants rates other uses at 2 out of 5.