The study investigates the spatial pattern dynamics of Senecio rivularis on different levels of population organization: genets and ramets. The tested null hypothesis was: in the expansion phase of a population, abundance and spatial pattern are affected by the number and diversity of genet clumps, in the stable phase with limited habitat resources population size is controlled mainly within independent clumps of genets. Spatiotemporal patterns of genets were studied within the entire population area and within selected clumps, respectively, while patterns of ramets were observed at a small scale. Additionally, data on genet survival, production of ramets, and rhizome disintegration were collected on the basis of 100 labelled genets in different clumps. The genet spatial pattern concerning ‘structure scale’ and ‘structure intensity’ was very variable on the level of genets but on the level of ramets it was regenerated close to the mean lifespan of genet, i.e. from several to up to 10 years. Variable spatial patterns of genets and ramets were affected by changes in the proportion of unitary and iterative genets, and by the contribution of these categories to the total number of ramets. Different factors seem to be important for the population dynamics in the phases of expansion and fluctuation, respectively: environmental conditions, plant features, and intrapopulation relations, driven by competition for space and habitat resources.