Background: Common ragweed, Ambrosia artemisiifolia L., is\u00a0an economically important worldwide plant invader, due to its huge production of seeds and allergenic pollen, while its range and impact are expected to increase in future. Knowledge of the population dynamics of this annual species is essential to understand what factors drive spatio-temporal variation in population growth, and can help assessing efficacy of management interventions at the population level. Detailed demographic surveys over multiple years are labour-intensive, but when multiple research groups join forces and work according to standardized protocols, it may be feasible to collect such in-depth data in multiple habitat types across a large geographic range and over larger time spans.Aim: We developed this field survey protocol to monitor the population dynamics of common ragweed (Ambrosia artemisiifolia L., Asteraceae) across Europe. It is designed to estimate all vital rates of a population (establishment of plants, plant survival, plant growth, reproduction, and seed survival), and study how they relate to plant density and individual plant size. It targets unmanaged field populations (to create a baseline), but could also be used for assessing managed populations with some adaptations.Methods: Plots of 0.25m2 are established in a field population of common ragweed. The population, plots and (randomly selected) marked common ragweed plants within these are monitored early in the growing season and are re-assessed at seed set, when in addition soil samples and reproductive plants are collected (adjacent to but outside the plots) for further analysis in the laboratory. Repeating\u00a0the procedure on the same plots in multiple years is essential to derive estimates of seed survival in the soil seed bank from year to year. Replicated monitoring in time (multiple years) and\/or space (multiple populations), and measuring (additional) environmental factors, is needed to relate the dynamics to environmental variables.\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0Protocols provided: i) list of materials, ii) the selection of a site, iii) setting up the survey, iv) monitoring, v) sampling of plants, soil and seeds, vii) lab analyses of samples (plant biomass, soil seed bank, soil texture and content, cleaning of aerial seed samples)Record forms provided: i) for registration of meta-data of the site, ii) for all measures taken in the field and in the lab; all in a pdf-version for printout to use in the field and in an excel-version for digitising dataOther material provided: i) field sheets (checklist for field work, legend to the record forms), ii) help tools (for mapping plants, for assigning unique numbers to plants)Optimisation: The protocol has been used to monitor over 50 populations across the European continent in 2014-2016 by members of the SMARTER Task Force Population Dynamics, within the framework of the EU-funded COST Action 'SMARTER' (FA1203, \u2018Sustainable management of Ambrosia artemisiifolia in Europe\u2019, 2013-2016). By yearly Task Force meetings, the protocol has been evaluated and improved to the current version.