Field competition experiment
The EG and DG E. annuus plants were germinated at 2-week intervals and transplanted individually into pots (9 × 9 × 9 cm). Six weeks after the germination of EG plants, both EG and DG plants were transplanted to the field spot in alternating order, 7 cm apart. To mimic the overwintering of natural E. annuus plants, transplanting was conducted in October 2020, and the plants were monitored until July 2021. Leaf herbivory of rosettes was screened by visually measuring the damaged portion of the total rosette. The rosette diameter was measured weekly from October 2020 to April 2021, when active flowering was started. The number of flowering plants was counted weekly from January 2021 until the flowering of the EG and DG plants was saturated. The total lengths of the branches were measured weekly from April to June 2021. The number of flowers was measured weekly from May to July 2021 when flower production was active. Thirty flowers were randomly chosen to measure the floral diameter. At the end of the flowering season (July), the above-ground parts of both plants were sampled and used for fresh and dry weight measurements.