The problem how plants as a sessile organisms survive in the heterogeneous environment, changes that are often unfavorable to life, remains one of the most pressing modern biology, especially in connection with forecasts of global climate change and increased man-made pressure. We discussed the available views about numerous types of plant life strategies and mechanisms of competition and coexistence in plant communities in the light of an adaptive essence of phenotypic plasticity and its ecological significance. Autotrophic type of nutrition eliminates competition for inorganic resources as they are unlimited. On our opinion, differences in ontogenesis duration, species biological and ecological traits, reproduction systems, and sequence of seasonal development, as well as plasticity of the plant structural and functional organization in ontogenesis provide plant coexistence in modern biotopes and thus their stability.