Carlina onopordifolia is long- lived monocarpic perennial plant, which repro- duces only generatively, however, it flowers and fruits only once in lifespan (10-20 yrs) and after seeds development it dies. Due to this type of re- production the abundance of population depends on amount of produced seeds, moreover the plant flowers more abundantly every 2-3 years. The plant is highly specialized in respect to habitat and micro-climate conditions. It grows on cal- careous and sun-heated slopes, where xerother- mic grasslands grow with contribution of species typical for steppe vegetation. In Poland it is a very rare species known only from seven isolated nat- ural stands in south and east part of the country. Differences and year-to-year fluctuations in the frequency and the abundance of generative and vegetative specimens in natural stands were stud- ied in 2006 and 2007 years. The regional differ- ences in leaf rosette size and size of inflorescences were examined. The abundance of population in all stands increased from ca. 13600 plants in 2006 to ca. 31950 in 2007. The G test revealed sig- nificant decrease in frequency of flowering plants vs. barren plants between the years in four of all seven stands. The significant differences in mean diameter of leaf rosettes (45; 49; 52 cm) and mean diameter of anthodium of generative specimens (7.17; 7.74; 8.27 cm) were observed in three the most geographically distinct and the most abun- dant populations. The mean values of leave rosette (44.20; 49.31 cm) and sizes of anthodiums (6.05; 7.61 cm) also changed significantly between the years 2006 and 2007, respectively for all data. It can be concluded that in all stands of the thistle in Poland the synchronization of blooming phase takes place. The observations implicate conclu- sions important for practice of monitoring which must be conducted at least for two vegetative sea- sons covering the whole phenology of the species in order to prevent the artifacts.