Asclepias syriaca (Asclepiadaceae) is a clonal plant, a kenophyte native to North America, and it is known for its ability to form colonies. We present here a modern distribution map of A. syriaca in Ukraine based on extensive research, including data from numerous herbaria, literature, open biodiversity databases, and our own field observations. Our findings indicate that the highest concentration of this species is found within the Forest-Steppe region. We conducted a comprehensive population study using traditional methods, identifying the above-ground shoot as the main unit of measurement. Our research focused on four population sites in the Left-Bank Forest-Steppe (Poltava Region) and one site in Ukrainian Polissya (Kyiv Region) for comparison. The populations studied are thriving and continuously expanding. Our results indicate that intraspecific competition (self-thinning) plays a significant role in the species' territorial expansion. Under the influence of climate change trends (particularly, warming and a decrease in annual precipitation) observed over the past 14 years, a shift in phenophases has been recorded: shoots of A. syriaca emerge approximately three weeks earlier than before. However, other population parameters have not shown significant changes.

Keywords: alien species, Asclepias syriaca, common milkweed, invasive species, population structure, population dynamics

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