This thesis describes the genus Hemerocallis, the trading with daylily from hybridizer to seller with emphasis on the Swedish market. The first part describes the daylilies biology its botany, breeding, production, pests and diseases. Also the tobacco ringspot nepovirus recently confirmed in Sweden is described. Since the breeding of daylily is mainly done in Florida topics like hardiness and influence of the climate are included. The first part is mainly based on literature studies, but also interviews with growers and breeders from Sweden, USA, Holland and Germany.