Stevia

Buyers pay for total steviol glycoside content and for the ratio between individual glycosides, because the individual compounds differ in sweetness and in aftertaste. Two crops of identical leaf weight can be worth very different amounts, and a grower cannot judge the value of a harvest by looking at it.

Soil suitability should be assessed with local soil survey information and, where available, field testing.

Glycoside concentration in the leaf rises to a peak around the beginning of flowering and declines once the plant commits to seed. Harvest is therefore cut at or just before that point, and a crop left a week or two too long is worth measurably less for the same weight of leaf.

Because flowering is triggered by shortening days, the date at which the crop must be cut is set by latitude and season rather than by the grower's schedule. Supplementary lighting is used in nurseries to hold mother plants vegetative, but a field crop simply has a deadline.

Stevia seed germinates poorly and unevenly and the resulting plants vary widely in glycoside content, so commercial planting uses rooted cuttings or plugs of a selected clone. Nursery capacity is therefore part of the production system, and the cost of planting material is a large share of establishment.

Where winters are mild the plant is perennial and is cut two or three times in a season and over several seasons, with the stand regrowing from the base after each cut. Cutting height determines regrowth vigour, and cutting too low weakens a stand that is meant to last years.

Fertilizer rates, timing, and forms should follow local soil tests and regional guidance. AgricultureID does not publish universal fertilizer recommendations.

Leaf is dried quickly after cutting to prevent degradation, then the leaf is separated from stem because stem dilutes the glycoside content of the delivered material. Leaf-to-stem ratio is part of the delivery specification and is a direct product of how the crop was cut and threshed.

Steviol glycosides are permitted as a sweetener under food law in many jurisdictions and specific purities and glycosides are defined in those approvals. The regulatory position, not the agronomy, has driven the crop's expansion, and it differs by country and by individual glycoside.

Stevia is in the daisy family with sunflower, lettuce and safflower, and it shares sclerotinia and septoria with them. A rotation that places it after another composite concentrates rather than breaks disease pressure.

Management combines resistant varieties, rotation, monitoring, and — where justified — locally authorized control products applied according to their labels.

Stevia rebaudiana is native to a limited area of Paraguay and adjacent Brazil, where it was used long before commercial interest, and production is now concentrated in China with substantial areas in Paraguay, Argentina, India, Vietnam and Kenya. The species has a much narrower natural range than its cultivated distribution suggests.