In the initial phase of growth in an oligo-humotrophic lake, Cladium mariscus forms a dense and tall sawgrass bed invading the open water in the form of a floating mat. High densities of submerged evergreen perennial stems of C. mariscus, over two metres high and abundantly fruiting, ensure its persistence, and form a natural barrier to the invasion of other species. Dense mats of sawgrass are formed as a result of clonal and rhizome growth. Although diaspore production is abundant under natural conditions, only vegetative propagation of stems was observed. In different variants of the experiment only seeds wintering on stems of mother plants were capable of germinating. Hard seed coats had an important effect on the germination capacity of seeds.

The effectiveness of renewal of a Tussilago farfara L. population after destruction of the plant cover was studied. This process proceded at a very intense rate mainly due to querilla type vegetative growth. In its successive years the renewing population was characterized by: 1) a dynamic spurt in the number of individuals in the first year after destruction, attaining a maximum the following year; 2) a complete lack of generative shoots in the first year; 3) high mortality of seedlings; 4) change in spatial structure; 5) increased differentiation in the way individual plants spread. Seven-year studies have shown that even drastic disturbances in the environment did not eliminate T. farfara, moreover, complete destruction of the plant cover created favourable conditions for population renewal

The effects of systematic cutting, fragmentation and burying on weeded and renewing fallow plots on the density and morphological properties of vegetative and generative Tussilago farfara shoots were studied. As the presence of other species increased on fallow plots, the T. farfara population regressed. Under such conditions, fragmentation and burying ensured the renewal and expansion of individuals and persistence of the population. On weeded plots, however, additional cultivation reduced the population density and mean values of the analyzed shoot parameters. These results show that systematic cultivation is a prerequisite for persistence of T. farfara populations. Its favourable effect is exerted through eliminating potential competitors

The survival, seedling and juvenile growth rates and the effectiveness of development and renewal of individuals obtained from seeds and rhizomes were studied. The results showed that the success of Tussilago farfara L. in colonizing disturbed environments, after its seeds reach the site and germinate, is a function of several of the important traits of this species: 1) tolerance of seedlings and juveniles to a wide range of changeable external conditions, 2) fast growth and development of individuals, 3) a high degree of adaptability in reaching successive stages of development, 4) querilla type growth, 5) intense spreading and renewal of individuals of generative and vegetative origin, 6) high effectiveness of vegetative reproduction, 7) adaptable allocation of resources to above-, and underground shoots

The paper evaluates the effect of fallowing on seasonal and multiyear dynamics, as well as on the spatial structure of <em>Tussilago farfara</em> population. In four years turfing and rapid increase in the size of grass populations - those of <em>Agropyron repens</em> (L.) PB. and <em>Dactylis glomerata</em> caused the elimination of <em>Tussilago farfara</em> population. The studies have showed that a decrease in the population size resulted from hampering of both vegetative and generative reproduction. The interspecific competition for available space seems to be a crucial factor limiting emergence of new shoots. In the agrocoenose big population size of <em>Tussilago farfara</em> remained throughout the studies.