We tested the extent to which reproductive effort by an iterocarpic native thistle Cirsium undulatum provided within-season tolerance for insect floral herbivory through plant response to apical damage. We imposed apical damage and used insecticide to reduce herbivory damage to manipulate plant response and potential outcomes in reproductive compensation. Data include: 1) detailed size and fecundity data per plant individual under different treatments; and 2) insect damage score and seeds produced per individual flower head. Resources in this dataset:Resource Title: Wavyleaf thistle individual plant data. File Name: West_2021 Wavyleaf plant data.csvResource Description: Includes detailed information on whole plant morphology (e.g., number of branches and flowerheads), fecundity, and insect damage estimates.Resource Title: Wavyleaf thistle per flowerhead data. File Name: West_2021 Wavyleaf flowerhead data.csvResource Description: Includes visual damage score and seed production estimate from individual flowerhead dissections.Resource Title: Wavyleaf thistle Plant and Flowerhead data description. File Name: West_2021 Wavyleaf dataset.txtResource Description: Explanation of variables and information on Wavyleaf thistle data files