The article analyses the motivation and wordformation structure of the name of the sunflower (bot. Helianthus annuus L.) in dialects of Slavonic languages according to the data given in the Slavonic Linguistic Atlas and in the national dialectal atlases. The characteristic reaction of this plant of American origin to the sunlight motivated the emergence of its names with a wordstem, which is continuation of the Proto Slavonic stem *sъln- in the entire Slavonic language territory. The wordformation type ‘derivative base + derivation suffix’ is typical for the West Slavonic, Slovenian, Ukrainian and Belarusian dialects. For Russian dialects, the characteristic wordformation model is ‘derivation prefix + derivative base + derivation suffix’. Composites like suncokret, suncogled, parallel to the structurally same Italian names girasole, mirasole and Greek name heliotropion, are typical for dialects of the South Slavonic macroarea (except Slovenian and part of the Croatian dialects).